Organic weed killer for gardens

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Weeds are the bane of every gardener, especially as the days heat up and vacation season starts. But short of hand-digging them every day, it can be a real challenge to stay on top of your weeds before they strangle out your veggies and flowers.

Here are 10 non-toxic ways to handle weeds in your garden…

Contents

Skip the Toxic Herbicides

Although hand-digging and hoeing are the most effective methods for removing weeds, it can be tempting to use a little Round-Up or other store-bought herbicide to make quick work of your weeds—especially if they’ve gotten a little out of hand. But there are some very important health and environmental reasons to avoid them.

A study by the Massachusetts Institute of Technology found that glyphosate (Round-Up) residue in food may act synergistically with other food-borne chemical residues and environmental toxins to disrupt normal body functions and lead to the development of Parkinson’s disease, infertility or cancer.

Indeed both the state of California and the World Health Organization have deemed glyphosate to be a probable carcinogen.

In 2009, a French study found that a filler ingredient used in Roundup called polyethoxylated tallowamine was more deadly to human cells than the main ingredient, glyphosate.

In the environment, glyphosate usage has led to the evolution of glyphosate-resistant weeds covering an estimated 120 million hectares globally. Glyphosate also chelates micronutrients in the soil, leading to decreased photosynthesis, decreased resistance to drought, and increased spread of disease. In fact, more than 40 plant diseases have been linked to glyphosate use.

Glyphosate is toxic to many beneficial micro- and macro-organisms including earthworms. It also harms soil microbes responsible for growth, mineral uptake and disease prevention. In sum, crops grown with or around glyphosate are simply less nutritious.

Glyphosate’s high water solubility makes it extremely toxic to many frog species and other aquatic life. On land, the major decline of Monarch butterfly populations is partially caused by glyphosate applications killing off the milkweed habitat that Monarch larvae need to feed and grow.

Finally, glyphosate has been found to contaminate ground water supplies as well as rain and air in Spain and the US, threatening our drinking water. Glyphosate has also been detected in the bloodstreams of Americans and Europeans at levels exceeding drinking water standards.

To avoid these serious long-term health and environmental effects, skip the Round-Up and other herbicides, and try some of these effective, organic methods to control your weeds instead.

Related

  • What is a GMO and Why Should You Care?
  • Organic Garden Disease Control
  • The Difference Between Open Pollinated, Hybrid and GMO Seeds

10 Organic Weed Control Methods

1. Mulching

Covering your garden soil with a layer of organic matter can smother and inhibit weeds, as well as prevent new seeds from germinating. Good sources of mulch include wood chips, compost, grass clippings, and straw. Just be sure not to get hay, which can contain a lot of unwanted seeds.

You can also put down ground cloth, newspaper, cardboard, old cotton curtains or bed sheets, landscape fabric, or other thick material on your soil to prevent weeds from growing through. This is especially helpful to do in your garden pathways before you put down gravel, stone or wood chips.

2. Crowding

Wide row planting beds shade the soil as the plants mature.

Weeds can’t take hold in your garden if there’s no space for them.

In ornamental beds, plant groundcovers and perennial plants to cover and shade the soil.

In your vegetable gardens, try either the Square-Foot gardening method or wide-row planting method so that your plant leaves will just touch each other at maturity. As the plants grow, their leaves will shade the bed and deprive weeds of sunlight.

3. Limit Tilling and Digging

Tilling or turning over your garden soil will bring new weed seeds to the surface. Instead, try using the no-till method of gardening or Lasagna gardening, where you disturb the soil as little as possible.

If you are planting seeds, only dig down as far as you need to plant them, instead of tilling up the entire bed. The no-till method also improves soil structure and fertility, and increases the population beneficial organisms in the soil.

4. Solarizing

Solarizing your soil involves covering an area of weedy ground with a clear, heavy plastic sheet. (Black plastic does not work as well.) This only works in full sun and warm weather where the heat will collect under the sheet and literally cook your weeds. Leave the sheet in place for 4 to 6 weeks, and remove only once all the weeds are brown and dry.

For even more effectiveness, till the soil to bring weed seeds to the surface, and let them sprout just before solarizing.

5. Fertilize and Irrigate Carefully

The nutrients and water you give to your garden will help weeds grow just as much as they will help the veggies and flowers you want. Only give your plants what they need.

Use drip irrigation, irrigation bags or olla pots to provide water only to the roots of your plants, not the empty spaces around them. Give heavy feeders like squash, tomatoes and cucumbers extra compost, but, feed crops like root vegetables much less.

6. Boiling Water

Boil a kettle of water and pour it over any weeds to burn them. This technique is great for weeds growing in the cracks of pavement and coming up in your garden paths. The water will cool as it runs off so it won’t hurt any plants you want to keep.

7. Vodka or Rubbing Alcohol

Try this weed-killing recipe on your annual weeds growing in full sun:

  • 2 ounces cheap vodka or rubbing alcohol
  • 2 cups of water
  • a couple drops of dish soap

Mix into a spray bottle. Spray on weeds to dry them out and kill them.

Be careful not to spray on any of your regular plants, because the alcohol will dry out whatever it hits. This spray does not work well in shady areas.

8. Vinegar

This vinegar mix is good for drying out weeds too, though you may have to apply it multiple times on weeds with a long taproot, like dandelion.

  • 1 gallon 5% white household vinegar
  • 1 cup table salt
  • 1 Tbsp. dish soap

Mix into a spray bottle and spray directly onto your weeds, making sure to avoid the plants you want. It works even better in full sun.

If you use 20% or 30% vinegar (available online), this formula will work much better, but the vinegar is so acidic, you will need to use gloves and goggles to ensure any spray doesn’t blow back and burn your skin or eyes.

9. Corn Gluten

Corn gluten meal is a byproduct of the corn milling process that just so happens to prevent weed seeds from germinating. It does nothing to kill weeds once they have sprouted, however.

Corn gluten meal is often applied to lawns to prevent crabgrass and dandelions from sprouting, but it can be used in other garden areas, after the seeds you want have sprouted.

It’s non-toxic, and if you buy certified organic corn gluten meal, there will be no GMOs or glyphosate residue. If you can’t find it in your local garden center, corn gluten meal is available online.

10. Flame weeders

A flame weeder is a wand connected to a propane tank which enables you to pass a flame over a weed in order to fatally heat the plant tissues. Flaming will only kill the leaves above the ground, not the roots, so you may need to flame your weeds a few times before they’re gone.

Flame weeders are extremely effective on all types of weeds, and if you have a large garden or small farm, they are worth the investment. Just take great care when using a flame weeder during a dry spell, when there is a risk of fire.

You can find flame weeders in garden and hardware stores, or online.

With so many great organic weed control methods to try, why would you ever grab a bottle of that toxic stuff?

What is your favorite way to kill weeds in your garden? Let me know in the comments!

Organic Weed Control

How to Kill Weeds with Homemade weed killer and other Natural Methods

A statement of fact is that you can’t prevent weeds 100%.

But it is a fact that you can limit, control or kill most of these unwanted trespassers with a homemade weed killer or other organic weed methods.

Politicians love to say, “The fact is…” Which gets us suspicious because proven “facts” are often the last things you can find.

With weeds though we have ways and means… natural, easy and safe. Fact is we’ve proven it.

Now it’s over to you…

Read on or skip to these recommendations. . . .

Change your soil to fix your weed problem—See main page on Garden Weeds
Smothering weeds
Vinegar as a homemade weed killer
Boiling Water to get rid of weeds
Flame and steam to kill weeds
Oil to eradicate weeds
Hand or hoe for organic weed control
Other natural weed control methods (chickens, tilth, solarisation etc.)
Corn gluten to stop weed seeds growing
Doubtful or dangerous dudes for killing weeds

Organic vs Chemicals

Organic weed killing methods are ‘contact’ killers. They work by destroying the plant matter that they touch. Do this enough and the weed has no greenery to carry out photosynthesis—it starves to death.

Chemical weed killers are mostly ‘systemic’. They are absorbed or taken up by the plant and work from within, destroying and killing the whole plant, roots and all.

NOTE: There are living things in the soil and I know you care about them because you are an organic gardener reading this page.

Good on you… keep our wriggling, scurrying, multiplying beneficial soil friends safe by following these few basic steps when you use organic weed control methods:

  • Sometimes it’s hard to pull or dig out weeds in paths or hard to reach places, and that’s when most of these natural weed zapping ideas are useful.
  • Use these methods judiciously, both to keep weeds from competing with your good plants and for a tidy property. Tidy, who cares, you exclaim! But remember, one weed seeding is as bad as two love-struck rabbits…
  • Horrible monster weeds, such as gorse, blackberry, huge thistles and the likes, are best tackled first by cutting down as much as you can and then using one of these organic weed killing methods on the regrowth, over and over if necessary.
  • For plants with long tap roots, such as dandelions and docks; and for hardy plants with a large root spread or rhizomes, such as some grasses and creepers, you will need to attack any new growth after the first assault. This may mean several applications or multiple goes throughout summer.
  • Choose a calm, sunny day with no rain forecasted. Spray drift from a breeze can be sad, and the hot sun helps certain sprays, especially vinegar, to burn into the plants.
  • Cover over, or peg/tie back any nearby plants you DON’T want to harm. If there’s any possibility of spray or splashes, better to be safe than sorry.
  • Attack the weeds only, avoiding the soil as much as possible. Spraying or burning the center or growing tip and sometimes the tops of the leaves is enough—no need to spray the undersides as you will probably do damage to surrounding plants and ground.
  • You also don’t want to unnecessarily kill insects, such as in mid-summer when native bees zip and hover over the ground, then dive down with their load of pollen where they’ve laid their eggs into their little round holes they’ve dug out—very often in the fine soil between cracks in pathways.

Smothering Weeds

Unflappable, cool gardeners don’t want to change the world; they just want to practice natural, easy ways to grow stuff. They like to get their hands in the dirt and they like to smother weeds before they become a problem.

HOW to be a weed smotherer

  1. Follow the no dig principles on this website. The basis of no dig gardening is to follow Mother Nature’s way and care for the soil from the top down. This almost gives you a weedless garden with a minimum of effort to fix any maverick stray weeds.
  2. Disturb your soil as little as possible, otherwise you will change the natural layers and bring up dormant, buried weed seeds. These will perk into life when they see light and feel air.
  3. Keep to paths and stepping stones. As well as keeping your soil aerated by not treading or wheeling things on it, it stops seeds being deposited there from traffic.
  4. Smother with mulch at least yearly. Use the organic mulch recommendations that you have available… paper, compost, leaves, and so on.
  5. If feasible, lay down drip irrigation so that water goes to plants roots and not all over the surface of the garden and paths.
  6. Smother by overplanting—planting ground covers in flower gardens is a great way to fill up any bare spaces between your ornamentals.

    In the veggie garden do the same. Plant some low growing companion plants, such as nasturtium or alyssum between your larger vegetables.

    Plant herbs, strawberries, vines and quick growing edibles such as radish and salad greens with slow coaches such as broccoli, or climbers like peas’n beans.

    The choices are many, just minimize open spaces.

Here’s how to fix a few grass seeds that have blown in…

Vinegar as a Home-made Weed Killer

Vinegar is probably the most well-known way to kill weeds naturally. It may take half a dozen, more or less, applications, but the plant will give up eventually. The surrounding soil pH may lower slightly if you spill some, but research shows that it will be back to normal within a week if you use ordinary household strength vinegar.

Common old grocery white vinegar containing 5% acetic acid is fine. If you can get a stronger 15-20% food grade solution it will work even better and need less applications.

Research has shown that vinegar with 20-30% or more acetic acid concentrate actually works differently. If the ground surrounding difficult weeds is saturated with this strong vinegar, it will lower the soil pH to such low levels as 3, which stops ANYTHING growing.

Microbes and soil biota will be safe and will go dormant until the pH comes back to normal over time, unless lime is added to speed it up.

This harsh vinegar is apparently left over from the wine industry and should only be used with such tough weeds that are normally almost inaccessible and away from growing areas, such as blackberry, bamboo, ivy and so on.

Acetic acid acts as a desiccant. It burns the leaves, draws out moisture and destroys the plants’ cell membranes. The leaves, stems and any other plant part it reaches will immediately die by simply drying and shrivelling up.

Handle carefully and don’t get any in your eyes. Any acetic acid concentration over 10% will also burn skin, and be especially dangerous to eyes.

HOW to use vinegar for weeds:

  1. Into a sprayer or squirter bottle, pour 1 litre of vinegar.
  2. Add a short squirt (about ½-1 teaspoon) of natural liquid soap to help the vinegar stick to the plants.
  3. To give extra oomph, you can put in 5 drops of an herbicidal essential oil such as citrus, clove, thyme or cinnamon oil.
  4. Put on lid and shake well, then apply to weeds.

Boiling Water to Get Rid of Weeds

This is such a handy way to keep on top of awkward weeds that, unless you’re short of water, it’s worth getting into the habit of using up any leftover water from boiling your kettle or eggs each time.

Be careful of your hands and feet, and keep children and pets away. Go slowly and concentrate when carrying the hot container.

HOW to boil a weed:

  1. Let’s say you’ve made some tea. Grab the jug and go outside and dribble the last of the hot water on that weed poking up by the drain… or by the side of the driveway.
  2. Or you notice some patches of newly sprouted grass or weed seeds in the middle of the gravel path. Boil up the kettle or pot and pour a thin trickle over this unwanted greenery. This should also kill some surface un-sprouted seeds too.

Flame and Steam to Kill Weeds

There’s nothing more satisfying than to watch something annoying in your life (weed), curl up its toes in a puff of smoke or hiss of steam.

Small weeds or a row of weeds on the edge of your garden, can be carefully annihilated, poof… just like that, with a quick pass of a propane flame, or steam gun.

The heat boils the water in the plants’ cells which causes them to burst and die.

HOW to kill weeds with a propane torch (sometimes called vapor or flame torches):

  1. Important: Choose a time after rain or at least when any nearby plants or mulch are soggy and wet. Also have a water hose handy and if possible a friend to follow you to dowse any sparks.
  2. For small gardens you can buy cans with the torch on the end. For larger areas there are propane tanks, like barbeque tanks, with a long gas hose and torch attachment which you may need a trolley/barrow/dolly to cart around.
  3. Simply do a quick swipe over the weeds, which will immediately boil the water inside the plants’ tissues. Don’t linger as it’s not necessary to burn them any longer and turn them into chips.
  4. Another reason for a quick swipe is that you may have nice bricks or pavers nearby and you don’t want to scar or heat these up… so just move the end of the flame back and forth, skimming the surface without stopping.

HOW to kill weeds with steam:

  1. A steam machine can be used as a weed control machine too. These machines are hired or sold for steam cleaning moss, mould, carpets, floors, yards, etc, and to steam old wallpaper off walls.
  2. It is best to use steam to kill weeds in large area, like yards and driveways. If you need to protect a plant, cut out the bottom from a large can, soda bottle, old hot-water bottle, bucket or something suitable, and put over plant.
  3. Hot steam is also very effective for going all the way, or a long way to eradicating woody weeds. As above, but this time put the protection (can, bucket, bottle etc) over the weed you want to destroy, then direct the steam into it. This stops surrounding plants from being harmed, plus concentrates the steam into one powerful spot.
  4. Wear shoes and cover up bare skin. Be careful of the cord to the electrical output, and keep pets and children away.

Oil to Eradicate Weeds

Oil suffocates plants so it makes a great herbicide. Some oils also strip the surface of the leaves which then dehydrates the plant.

Cheap vegetable oils, such as canola and sunflower are biodegradable and will be broken down by soil bacteria.

Gasoline, old engine and diesel oil are toxic to the soil, so don’t use these on garden weeds.

Many herbal and plant oils contain natural pesticide and herbicide properties. They can be mixed with other substances such as vinegar and soap to safely eliminate weeds. These oils are often found in organic preparations in garden shops, and include d-limonene, or citrus oil extract, neem oil, castor oil, pine oil, cinnamon, clove and thyme oil. Cinnamon for example contains eugenol, a particularly potent herbicide.

HOW to kill weeds with oil:

  1. Dribble the oil you have chosen or the homemade mixture containing oil, onto the weed so that it coats and smothers it.
  2. With such weeds as oxalis/soursobs trickle enough oil onto the plant and any bulbils you can see or disturb, so that they are smothered.

Organic Weed Control—By Hand or Hoe—ho hum

When the going’s tough, the tough get going, so they say. Where are ‘they’ though to come and help?

Many people, and me too, find a spot of weeding rather pleasant. Little and often is good; never is better say some! I say enjoy…

HOW to control those weeds before they control you:

  1. If your garden is in full production mode, say in mid-summer, you don’t want to disturb your veggies, flowers and soil structure by yanking or digging out stubborn large or deep weeds.
  2. So in some cases if you have a serious weed problem amongst the vegetable patch, at least make sure you cut off all flower and seed heads of weeds to stop them reproducing.
  3. And if necessary, you can carefully strip down any weedy stems and leaves that are crowding out your good plants, then after harvesting, you can fix the regrowth and roots for good.
  4. Otherwise for normal weeding, the best time is when the soil is damp or wet. Give a pull and most weeds glide out like a figure skater. Use a trowel or little weeder tool to help if needed.
  5. Carry a box or bucket and put the weeds in and dump in compost or where you want them to rot, or make weed tea.
  6. OR choose a sunny day and leave them on the ground, roots upturned to fry in the sun.
  7. If you hoe weeds, just disturb an inch or two of soil and let the sun bake the broken weeds, then go over again for any resprouting ones.
  8. Some people practice weed control by turning over any clods of weeds, such as grass clumps or thickly matted weeds and leaving them upside down. Then the plot is quickly planted up with an aggressive crop, like spuds, which grow and are harvested all before any of these topsy-turvy weeds find their feet again.
  9. Weeds with bulbs, such as onion weed and oxalis/soursobs are best methodically removed with a trowel, plant by plant, bulb by bulb (sob, sniff).
  10. With oxalis it’s best to dig out that long soft root in spring before it forms those ratbag baby bulbs. Also at this time the ground should be damp and easy to work.
  11. If you don’t get all the bulbs, keep at it and any time you see those leaves poke their pretty little heads up, send them to their next life. Also use the oil technique—as described above.
  12. Large woody weeds, like ivy and other vines, plus weeds with tap roots will need to be dug out with a spade.
  13. Enjoy—it’s so much better, cheaper and more useful than going to the gym for exercise!

Other natural weed control methods (chickens, tilth, overplanting, solarisation etc)

Soaps: Herbicidal soaps are sold to kill weeds. They work well and you can also use them as a base then add other ingredients, such as essential oils, to enhance their power.

Herbicidal soaps (Ammoniated Soap of Fatty Acids or potassium soap of fatty acid) are harmless to the environment, and they work by stripping the surface coating on leaf surfaces, causing desiccation or dehydration.

Chickens: Darling creatures and so good at scavenging in the garden and lightly tilling the soil… as well as egg laying.

If your chickens run free, it’s best to have them under fruit trees or in bushy garden, because anything else will be undermined in the search for little critters, or eaten because of the nice green leaves and seeds.

For garden use, either make or buy a moveable frame house of chicken wire with wheels on one end, that is just big enough for a few chickens and light enough to move around the garden (a small, easy to make A-frame works well).

Of course, at the end of summer, you may want to let your chickens run amok and clean up the garden, weeds and pests alike, before you do what you want to do for winter. Chickens will happily scratch and peck out weed bulbs and bulblets, going deep for this treat.

Tilth and sun: This is a favourite organic farmer’s or market gardener’s way to control weeds, but home gardeners can use the idea successfully.

Tilling, even lightly, does expose buried seeds that may burst into life when they get air and light, so keep your cultivation shallow.

Lightly run a shallow tilth machine or hand tool over the soil, exposing and if possible turning over any weeds, then leave the sun to bake the living daylights out of them.

Although it’s not the real deal, no dig way, these new machines are earth friendly enough to just go through the top layer without upsetting the living layers of soil that have built up over time.

Corn Gluten to Stop Weed Seeds Growing

Corn gluten is called a pre-emergence weed killer… it’s definitely the sharpest trick in the box for stopping seeds from sprouting. It is a natural by-product of processing corn or maize into corn meal, which is used in foods like chips, tacos, animal and pet foods.

Like a one-armed paper-hanger, corn gluten is useless for most things… except for those lurking weed seeds. It has an oily coating and inhibits the formation of roots.

It does not harm existing plants and as a bonus this weed seed terminator has high nitrogen content, so it feeds your soil as well.

Corn gluten is available at stockfeed outlets and garden centres. You may have trouble finding an organic, that is non GMO supply.

HOW to use Corn Gluten to prevent weed seed sprouting:

  1. In early spring and again late summer if necessary, sprinkle over area where weeds were or you know there are unwanted seeds. Use according to packet instructions or at 1 kg per 9.30 square meters (2 lbs/100 sq ft).
  2. Rake lightly in, or if putting down paver cracks, sprinkle with sand of gravel to stop it being washed out.
  3. Wait 6 weeks before the corn gluten has completely broken down before you sow desirable seeds.

Doubtful or dangerous dudes for killing weeds

Salt: Vast amounts of salt are spread in countries to melt snow which covers roads and pathways that are essential for transport use. This salt often washes onto the land and can cause high soil salinity which limits many plants from growing.

This salt also slowly leaches down and finds its way to the lowest levels going into rivers, lakes and the sea. It causes harm to water life both flora and fauna, as well as promotes unwanted water weeds and algae.

Salt (sodium chloride) is natural, but it doesn’t biodegrade, so if you want to use it on some weeds, do so sparingly and only on spot weeds in difficult places or in cracks in paths or driveways. Make sure your vegetables and other prized plants are not growing down the line or nearby as they may suffer.

Plastic: Nuking weeds with plastic works brilliantly… unfortunately. Plastic is a wonderful invention, but like many wonderful things, it gets abused, overused and the unintended consequences thunder in… and in plastic’s case, it is clearly becoming a no-brainer shocker of a problem.

Stepping off my platform for a moment, I’m not against using plastic, BUT only used plastic. I don’t buy new plastic, unless there’s no alternative (think, my computer). I try to avoid plastic packaging, and I certainly will not buy any of these plastic weed mats, grow bags and other garden stuff.

But by all means, like me, make use of other gardeners’ hand-me-downs. If you find a pile of plastic plant pots, some polystyrene seed trays, plastic mesh, sheeting, and any of the 101 other plastic fantastic paraphernalia going begging—grab it and give it another use.

HOW to use plastic sheeting for soil solarization:

  • Soil solarisation kills weeds and can actually sterilize the soil and kill all life if hot enough. You need plenty of sun for this method to work.
  • There is some debate about the merits of black or transparent plastic. Transparent plastic lets the light in so will encourage the weeds to grow initially, but only for them to get severely burnt by the direct sunlight… as well as allowing heat to build up under the clear plastic. Black plastic absorbs the heat, blocks the light and cooks the weeds and soil underneath.
  • If you use transparent plastic, have the weedy area as dry as possible, so that those weeds have to cope with lack of water as well as heat.
  • With black plastic it’s more effective to wet the area first to help really stew the weeds.
  • Whichever you use, lay the sheet, or large bags over the area of weeds you want to kill. Overlap generously and secure with rocks, bricks, boards, wire pins or whatever is heavy enough. Pile soil around the edge if you can. The closer to the ground you can make the plastic, the less air there is for the struggling weeds.
  • After a month or more in good hot sun, you may be able to see enough damage so that you can now make your garden there. A hand’s length down should be dead as a dodo, roots and all.
  • In some climates, and especially with deep rooted crab, elephant, kikuyu type grasses, you may need to leave the plastic there for up to a year for total weed control. Keep your eyes open to grass tentacles surfacing many meters away, even under driveways!

Happy weeding,
Now all you have to worry about is a small equation,
which goes something like this. . .

Wind plus birds plus neighbors = Neighborly weeds dropping in for a visit.

Back to HOME page: No Dig Vegetable Garden

Uncategorized

How to Kill Weeds Without Harmful Chemicals

It’s that time of the year when our lawns are still dormant, but cool seasonal weeds are beginning to pop up in the lawn and landscape. The 14th century reformer, Martin Luther, once said, “You can’t stop a bird from flying over (or landing on) your head, but you can stop it from building a nest in your hair.” While no lawn or garden will ever be 100% weed free, we can keep the weeds from taking over your lawn. Organic weed control involves a multitude of gardening techniques and it is quite possible to have a weed free lawn & garden and not use toxic synthetic chemicals.

Organic weed control is much more than killing weeds safely. It is first about growing healthy turf in fertile soil and minimizing weed pressure. Organic weed control is further achieved by using an Integrated Pest Management (IPM) program to establish weed thresholds, prevent weeds, and eradicate as a last resort.

There is no quick fix, magic spray weed killer in organic lawn care. Organic weed control is more about the holistic organic management of the lawn and soil, which results in fewer weeds. The theory (and practice) being that a healthy lawn and soil will promote turf growth which will out-compete weeds.

The first thing to understand is that the health of the soil is the key point in creating a weed free lawn. Healthy soil yields a healthy lawn and landscaping that will resist weeds. Use organic fertilizers, compost and organic soil amendments to build the health of your soil. Sow grass seed in the spring to thicken up your lawn. Trim and thin out the canopy of your trees so that your lawn receives the proper amount of sunlight. (Remember, Bermuda grass needs a minimum of 8 to 10 hours of direct sunlight every day to be thick and healthy. St. Augustine needs a minimum of 4 hours of direct sunlight.) Also, over watering or areas in your lawn where the water drains poorly and the soil stays moist will also cause your lawn to be thin and sickly. Our southern grasses must completely dry out between waterings in order for them to be green, lush and weed resistant.

Correct cultivation practices must be performed to reduce the opportunity for weeds to thrive. Weeds thrive on weak, stressed out turf and compacted, unhealthy soil. Eliminate those conditions and grass will win over weeds.

While “scalping” your lawn is a fairly common practice, it will actually weaken your lawn’s root system and make your turf susceptible to a variety of weeds and diseases.

  • Mow at the highest level possible to encourage a dense lush, lawn capable crowding out of weeds.
  • Reduce soil compaction by aerating your lawn.
  • Improve water and nutrient uptake by de-thatching with our microbial compost tea.
  • Topdress with Spriggs Brothers organicly enriched compost and soil amendments.
  • Re-seed bare spots or thin lawns this spring to avoid them from being taken over by weeds.
  • Avoid scalping the lawn when mowing. Damaged crowns recover very slowly and give weeds an opportunity to establish.
  • Water deeply and infrequently, maintain adequate soil moisture but do not over-water.
  • Apply corn gluten meal, an organic pre-emergent, @ 20 lbs per 1,000 sq ft in your lawn in mid February and a second application 4 to 6 weeks later (March/April). An average size lawn will need 80 to 120 lbs of organic pre-emergent per application. Corn Gluten Meal suppresses seed germination and provides a quick green up for your lawn.
  1. Weeding by Hand

    Use a gardening tool to remove weeds from your lawn and landscape, or remove them by hand. Some people are choosing a more dramatic organic gardening measure to control their weed populations. In the West, hiring a herd of goats to eat weeds is quickly gaining popularity. Goats prefer to eat brush, leaves and twigs. They munch grass only as a last resort.
    Now, I don’t think we need to resort to goats. But hiring your kids (or hiring Spriggs Brothers) to spend a few hours hand weeding will keep the weeds from taking over your lawn and landscaping. The best way to manually pull weeds is to grab the plant close to the ground, encircling its leaves with the fingers of one hand, using a small-bladed knife or sharp-edged weeding tool. Use it in the soil to slide under the roots of the weed to loosen them and help remove the plant from the soil. Be sure you get the roots of the weed. Throw the weeds into a compost pile or the trash. Do not leave the pulled weeds on the ground. Many weeds have seeds that will germinate and multiply your weed problem.

  2. Spot spray the weeds with an organic post-emergent

    Now, while the grass is dormant and the weeds are green, is the best time to spot spray the lawn with an organic herbicide. Acetic acid in vinegar has plant killing properties and can be used as a non-selective weed killer. Household vinegar does not get above 5% acetic acid and weeds would need repeated applications.
    We recommend using a 10% vinegar based herbicide with orange oil, molasses and bio wash. Spraying a vinegar herbicide on dormant grass won’t harm your turf, but if you over seeded with winter rye or fescue, the vinegar will kill the cool season grass. You can buy the organic postemergent at the organic store. If you don’t know where to buy the post-emergent, we will sell you a gallon of our recipe, or you can hire us to spray your lawn for weeds.

  3. Let nature burn out your weeds in your lawn

    Henbit Annual Poe (Bluegrass) Many of your cool season weeds, but not all weeds, will die out when the temperatures get to be in the mid to upper 80 degree mark. Henbit, annual poe (bluegrass), and other cool season weeds will naturally die off in the warmer temperatures, especially if they get direct sunlight. When the temperature warms up, usually April/May, mow and bag your lawn to 3/4 an inch shorter than normal for two weeks in a row. Put down a high nitrogen organic fertilizer or corn gluten meal, and your weeds will naturally die and disappear.
    We recommend that you diligently follow the first two steps in steps in February and March and then when the temperature warms up, nature will finish off the job. Using multiple methods is the key to successful weed control. Combining different strategies brings excellent results.

  4. Control the weeds in your flowerbeds

    A good 2 to 3 inch layer of shredded mulch is a great way to prevent weeds from taking root in your landscaping and gardens. Avoid pine bark or other mulch “chips”, as these will wash away after a heavy rain. After hand weeding the flowerbeds, put down a 1/8 inch layer of newspapers as an organic weed barrier. Wet it down so it won’t blow away. Then add a 2 to 3 inch layer of hardwood or cedar mulch. The newspaper will compost into the soil and along with the mulch will help build healthy soil. The newspapers will be an effective weed block for 6 months, or about the same time you need to replenish your mulch in the fall.
    We recommend that you add lava sand, green sand, corn meal and molasses to your flowerbeds before you put down your fresh layer of mulch this spring. Work the soil amendments into the soil, loosen the soil up to alleviate soil compaction and to get oxygen and nutrients around the root zone or your shrubs and perennials.

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Some people might feel torn between using a weed killer that works and one that isn’t toxic to the environment. The good news is, now you can have both.

There are some great organic weed killers out there that take care of your weed problem without causing collateral damage.

There are a lot of different types of products out there which can make it tough to find the best organic weed killers. That’s why we did the research for you, to help you find the perfect solution for your lawn or garden.

Benefits of Using Organic Weed Killer

A lot of gardeners prefer to use organic, more natural methods for weed control as opposed to harsh, toxic chemicals that can damage the surrounding plants and maybe even contaminate groundwater.

Using organic weed killers is also a better choice for your family, especially if you have pets or young children running around your yard.

So, what makes chemical weed killers so bad? The main ingredient, glyphosate, builds up in the soil and sticks around for a long time. With enough exposure, it can lead to genetic mutations or cause cancer.

The main difference between chemical and organic weed killers is that organic weed killers do not use glyphosate so they’re much safer. As we’ll see, they also work in a completely different want than chemical herbicides.

Another thing that is great about organic weed killers is that they don’t have the same potent, chemical odor that traditional weed killers do. Because a lot of them are derived from essential oils, some of them even smell good, believe it or not.

Finally, when you use an organic weed killer, you don’t have to wait days to use your yard again. This is particularly great if you have kids or pets that love to spend time roaming around the yard. You can usually replant in the area pretty quickly, too.

The 8 Best Organic Weed Killers for Garden & Lawn

There are a lot of great organic weed killers out there. If you’re not sure which one to buy or are feeling a bit overwhelmed, here are eight of the best ones available.

Picture Organic Weed Killer Weed Link
Green Gobbler Vinegar Weed & Grass Killer Crabgrass, Dandelions, Clover Weeds, White Clover, Moss, etc.
Natural Armor Weed & Grass Killer 250+ Types of Weeds & Grasses
Doctor Kirchner Natural Weed Killer All Types of Weeds & Grass
ECO GARDEN PRO – 100% White Vinegar Organic Weed Killer Dandelions, Clover, Chickweed, Dollar Weed, Thistle, Crabgrass, Moss, General Weeds & Grasses…
BioSafe Weed Control Concentrate Variety of Weeds & Grasses
Weed Slayer Organic Grass and Weed Control All Types of Weeds & Grass
OrganicMatters Natural Weed Killer Spray 250+ Weed Types
Bonide Fast Acting Weed and Grass Killer Grassy Weeds & Broadleaf Weeds

Best Organic Weed Killer Reviews

1. Green Gobbler Vinegar Weed & Grass Killer

This weed killer from Green Gobbler kills weeds in less than 24 hours. The main ingredient is acetic acid, derived from corn. Acetic acid is the same material found in table vinegar only this concentration is four times as strong.

Since this product is certified organic, it’s ideal for residential or agricultural use. You can use it on driveways, mulch beds, farmlands, and more. It’s effective against all kinds of weeds, including white clover, moss, dandelions, and crabgrass and it’s ready to go right out of the bottle.

Apply using the included sprayer. For best results, use on a calm sunny day and mix with a surfactant. One of the best things about this product is that it comes with a 30-day money-back guarantee. If you’re not happy, Green Gobbler will refund your money with no questions asked.

2. Natural Armor Weed & Grass Killer

Another great option is from Natural Armor, a family-owned company dedicated to its customers and the environment. This organic formula is chemical-free with no glyphosate and kills more than 250 types of grasses and weeds.

Because this weed killer is biodegradable, non-toxic, and environmentally friendly, it’s safe for your family and pets as well as groundwater, birds, and fish in the area. The bottle comes with a sprayer and is ready to apply, no mixing or diluting required.

You should see results in as little as 24 hours, if not sooner. We love that this product also comes with a 100% money-back guarantee. If you’re not satisfied with the way it works, Natural Armor will give you a hassle-free refund.

3. Doctor Kirchner Natural Weed Killer

Doctor Kirchner uses saltwater, food-grade commercial-strength vinegar, and soap to create this powerful and effective weed killer. You don’t have to mix or dilute it, just pour the liquid weed killer into a spray bottle and apply.

This formula was designed to take care of weeds without harming the surrounding environment. It’s pet-friendly, kid-friendly, and completely safe when used as directed. Spray until the weeds are saturated and wait. That’s it! Results are visible within hours with peak results between 12 and 24 hours.

Something great about this product is that it has a really long shelf life so you buy a large bottle, use what you need, and save the rest for when you need it. Every bottle is proudly made in Fort Pierce, Florida and starts with ocean water collected at high tide. You can’t get more natural than that.

4. ECO GARDEN PRO – 100% White Vinegar Organic Weed Killer

This formula from Eco Garden Solutions is extremely environmentally friendly. All of the ingredients are selected to be safe for not only kids and pets but also fish, bees, and any livestock that may come into contact with it.

Because it’s so safe, you can use this product just about anywhere. It’s made of natural white vinegar, Himalayan rock salt, plant activators, and co-factors that eliminate a variety of weeds, including clover, dandelion, crabgrass, white clover, thistle, and more.

Eco Garden Solutions is a great company, too. They only use pharmaceutical-grade ingredients that are sustainably sourced whenever possible. Each bottle is backed by a 100% satisfaction guarantee. If you’re not happy, they’ll issue you a full refund.

5. BioSafe Weed Control Concentrate

If you’re looking for something that works fast, take a look at this product from Biosafe Systems. It kills unwanted grasses and weeds in as little as two hours and is effective against liverwort, spurge, crabgrass, ragweed, dandelions, and more.

Something we really like about this product is that it won’t travel through the soil and harm surrounding plants. Plus, you can replant in the same area only four days after application.

This product works best when it’s applied to weeds that are a little wet from rain or dew. Because it begins to work on contact, it’s easy to see where you’ve applied it which helps avoid healthy plants. The formula works better in warmer weather but is effective at any time.

6. Weed Slayer Organic Herbicide Natural Grass and Weed Control

With a name like Weed Slayer, you can bet this one gets the job done. This formula is made from a plant-based herbicide that’s derived from clove essential oil called eugenol, a natural alternative to glyphosate that’s safe for your family and the environment.

This product is a little different than what we’ve seen so far in that you have to mix it. The weed killer comes with a quart of AgroGold. Just mix the two solutions in equal parts and mix them with water prior to application. Easy-to-understand instructions are included.

Something that we really like about this product is the smell. Since it’s derived from essential oils, it has a pleasant odor when you spray it. This product works a little slower than some of the other products we chose but it’s overall effective and extremely safe.

7. OrganicMatters Natural Weed Killer Spray

OrganicMatters natural weed killer is made using safe, natural, organic ingredients and kills more than 250 different types of weeds, including dandelions and crabgrass. It contains no glyphosate and is safe to use around mulch, walkways, wells, and water systems.

This product is ready-to-use and includes a heavy-duty sprayer that attaches right to the bottle. Just attach it and you’re ready to get spraying! It dries quickly and starts working in less than 24 hours. One gallon covers approximately 1,000 square feet.

Since this formula is all-natural, it’s safe to use around your family and pets as well as bees, birds, butterflies, and other wildlife. If you’re not happy with your results or unsatisfied for any reason, contact the company within 30 days of purchase for a full refund.

8. Bonide Fast Acting Weed and Grass Killer

Finally, we recommend this weed killer from Bonide. It treats a variety of grassy weeds and broadleaf plants with results in as little as a few hours. Make sure you check out the included instructions for specifics on how to handle each type of plant.

Something we really like about this one is that, once it dries, it’s waterproof so it keeps working, even if the weather turns later in the day. You can use it in temperatures as low as 40 degrees F and it’s safe around mature trees, borders, driveways, even school grounds.

This product must be mixed with water before application, roughly one part weed killer to three parts water. A measuring cup is included so you can get the proportions correct. Just mix well and use a spray bottle to apply. The main ingredients are citric acid and clove oil so it smells great, too.

What is the Best Organic Weed Killer?

All of the products that we included in this review are great but, if we had to choose one, we’d go with Green Gobbler Vinegar Weed & Grass Killer. We love that it gets results in less than 24 hours and uses acetic acid derived from corn as the main ingredient.

A lot of people try to use white vinegar to kill weeds. Well, this product uses the same acid found in vinegar only it’s four times as strong which makes it much more effective. It’s ready to use right from the bottle and includes a sprayer so you don’t need anything extra to apply.

Another reason we highly recommend this product is that it comes with a 30-day money-back guarantee. If you try it and it doesn’t work or you’re not happy with the results, contact Green Gobbler for a refund, no questions asked.

How Does Organic Weed Killer Work?

Organic weed killers work a little differently than chemical weed killers but their method for killing weeds depends on the active ingredient. The products we chose to use a few different active ingredients. Here’s how they work.

Acetic Acid or Vinegar

Acetic acid is the acid present in white vinegar but at a much higher concentration. So, they actually work in the same way only white vinegar will likely take a lot longer to have the same effect on the weeds.

Weed killers that use acetic acid as the main ingredient work directly on the leaves and should cause browning within 24 hours. Younger plants are usually more responsive to vinegar while older, hardier plants require the more powerful acetic acid.

Because these weed killers work on the leaves and the parts of the plant above ground, you may need to use several applications in order to get the root. If not, the weeds will reappear in a few weeks. That said, weed killers with a high concentration of acetic acid may get the root sooner.

Note that acetic acid is, obviously, acidic and may temporarily raise the acidity of the surrounding soil. This is temporary and typically resolves on its own when rain or watering rinses away the residue.

Salt or Saltwater

The best way to understand how salt and saltwater work as a weed killer is to think about an ocean beach. Part of the reason why plants don’t grow in the sand is that the constant exposure to saltwater removes all the moisture and nutrients. This is exactly how it works on weeds.

Applying an organic weed killer that uses salt as an active ingredient dries out the weed and the surrounding soil. Over-applying can cause bald spots in the soil and cause some short-term damage so you have to be careful to apply as precisely as possible.

One of the best places to use this type of weed killer is in cracks along sidewalks, roads, and walkways. Because there isn’t a lot of grass or other growth in the area, you don’t have to be quite as careful about precise application.

Eugenol

Eugenol is a compound found primarily in clove essential oil which is a common ingredient in organic weed killers. It works in a similar way as acetic acid in that it destroys the outside of the leaves, causing cell leakage and death.

Also like acetic acid, eugenol is good at killing the parts of the weed above ground but isn’t the best choice for weeds with extensive root systems or those with bulbs, tubules, or rhizomes in the soil.

Still, these weed killers are appropriate and very effective in certain situations, including along the edges of buildings and walkways and for treating spot growth of small, immature weeds.

Do I Need a Surfactant?

You may have noticed that some of these products recommend using a surfactant for more effective results. What exactly is a surfactant and why do you need one?

Most organic weed killers are applied directly to the leaves of the plant but most leaves have a thick, waxy coating that’s a little difficult to penetrate. Water, an ingredient in most weed killers, simply beads off and rolls down the plant.

This is where a surfactant comes in.

A surfactant is something that allows things to blend, stick, and work better. They’re common in a lot of chemical reactions but, for our purposes, surfactants help break down the waxy surface of the leaf and hold the weed killer in place so it’s more readily absorbed.

Using a surfactant makes weed killers more effective because it prevents it from being washed away and gives the weed killer the time it needs to work effectively. Some of these products ask that you use an additional surfactant while others may already have one included in the mixture.

Do you need a surfactant? Not necessarily because the weed killer you choose may already have one added. That said, if you choose a product that recommends using a surfactant, it’s a good idea to do so. You’re likely to get better results.

Conclusion

There’s a lot to think about when it comes to choosing the best organic weed killer. There are a lot of great products out there and, while none of them use the same toxic ingredients as chemical weed killers, they work in different ways.

We think all of these products are great but we highly recommend Green Gobbler Vinegar Weed & Grass Killer. It works within 24 hours and uses acetic acid derived from corn as the main ingredient. It’s like white vinegar on steroids and is effective without harming the environment.

Another great reason to give it a try is that it’s backed by a 30-day money-back satisfaction guarantee. If you’ve never tried an organic weed killer before, this is a great way to give a try. What do you have to lose?

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Large Area Weed Killer

By Ellen Brown

Q: I want to use a homemade, non-toxic weed killer to kill off weeds in two large garden areas in my back yard. Spraying with a small spray bottle is not reasonable. Could someone give me a recipe or a conversion that would work in an Ortho bottle that I can connect to my garden hose?

KJV from Wisconsin

A:

KJV,

This recipe is very strong and will essentially kill the soil, and everything growing in it, wherever you apply it (including any beneficial microbes). It is not selective, meaning it will kill your ornamentals along with the weeds. If used heavily, you may have trouble growing new plants in areas where it’s used unless you bring in some new soil. Don’t use it on or near concrete or apply it on windy days. For best results, apply on a hot day and wait at least 24 hours after applying.

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Recipe:

  1. Mix 1 pound of salt with one gallon of white vinegar.
  2. Stir until the salt dissolves.
  3. Mix in one teaspoon of liquid soap.

About The Author: Ellen Brown is our Green Living and Gardening Expert. Ellen Brown is an environmental writer and photographer and the owner of Sustainable Media, an environmental media company that specializes in helping businesses and organizations promote eco-friendly products and services. Contact her on the web at http://www.sustainable-media.com

Answers:

Well, I know that if you pour ordinary salt and water on weeds they die off after a few days. Maybe you could use a strong salt solution? It would be eco friendly and cheap too.
Let me know how it goes if you try it.

Chicky (09/03/2004)

By Louise

I know that I have taken vinegar and put it in a spray bottle and sprayed it on the weeds and in a couple of days the weeds were gone. Just be careful that you don’t spray it directly on the plants. (09/13/2004)

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By Jenny

This isn’t exactly what you’re looking for, and it’s not a quick fix, but you can lay down wet newspaper (at least six sheets thick, in my opinion). Cover with sticks, rocks, dirt, etc. so it doesn’t blow away. Next year the area should be clear of weeds and ready to be worked for a garden, lawn, or whatever. Good luck. (05/02/2009)

By A

Where Can I Get Organic Weed?

Back in the day, you assumed that pot was grown more or less organically, just from the vibe of the dready guy who sold it to you at the very least. Now that legal weed is a $10 billion industry, and folks like John Boehner, the straight-laced former Republican speaker of the U.S. House of Representatives, are looking to plow into those profits, it’s not unreasonable to imagine that industrial weed might have more in common with industrial agriculture than with the old-school backwoods pot grower ethos.

For the most part, it does. But unlike the rest of agriculture, there is no federal oversight of marijuana production (because the feds don’t recognize it as a lawful crop), which means there’s no one telling industrial growers which agrichemicals can and can’t be used. This lack of federal involvement in the legal marijuana industry also means you won’t find USDA-certified organic weed on the shelf at your local dispensary. But it does exist under other names.

The question of how to obtain organic weed brings up a slew of other questions, which we unpack below.

What Are the Environmental Impacts of Cannabis Cultivation?

The answer varies depending on the context.

Old-school guerilla-style plantings in Northern California aren’t as “green” as you might imagine. While these growers may be less inclined to spray agrichemicals, their methods are irresponsible in less obvious ways. Illicit plantings are often on steep land where erosion is problematic, for example, and may require unsustainable quantities of irrigation water from nearby streams. The negative impacts of this kind of outdoor cultivation on watershed health have been well-documented.

Legal marijuana cultivation, on the other hand, typically occurs indoors in tightly controlled settings where photosynthesis is stimulated not by the sun’s rays, but by huge light fixtures that slurp energy from the grid day and night. Water use is relatively modest with indoor cannabis cultivation, and fertilizers and pesticides can do little damage to the environment when contained in a grow room, but the greenhouse gas emissions associated with the all those grow lights is worrisome.

The number of legal outdoor farms is starting to grow, in part because the cost of electricity to produce the crop indoors is so steep (and an unnecessary expense if your main reason for growing indoors is to keep the plants hidden from the authorities). To obtain maximum yields, marijuana requires copious irrigation, fertilizer, and often pesticide use, so it’s likely that legal outdoor farms will have all the environmental impacts associated with comparable high-input crops, like corn.

“There will be no such thing as USDA organic marijuana until the feds legalize the crop.”

What Are the Health Impacts of Smoking Weed Grown with Chemicals?

While there is little evidence of people getting sick or dying from consuming marijuana laced with pesticides, shockingly high concentrations of toxic chemicals have been found in legally-obtained samples.

One study found pesticide residues at levels above 100,000 parts per billion – several orders of magnitude greater than the what is considered safe for consumption. In 2016, officials in Colorado, the first state to legalize recreational marijuana, found that 49 percent of samples tested contained unapproved pesticides. There have been scores of cannabis product recalls due to pesticide residues.

It’s worth noting that most research on the health impacts of pesticides focuses on worker exposure or consumption of food crops – not on crops that are smoked, which may actually pose greater hazards. You’d think such research had been done to assess the dangers of agrichemical use on tobacco, but apparently this isn’t the case. As Slate noted in 2016, “the EPA has not assessed the long-term risk of pesticides used on tobacco, because it has said the health risks of smoking cigarettes are so bad as to outweigh the pesticide risks.”

As you might expect, obtaining federal research grants to study pesticide use on a federally-banned crop is difficult. The federal status of the plant also makes pesticide regulations, which are typically set by the EPA, full of ambiguity. Lacking a national framework, a patchwork of state-level regulations have emerged regarding both pesticide use and the testing of marijuana products for consumer safety, but implementation has been slow and spotty.

Why Can’t I Find Legal Cannabis with the Organic Seal?

Organic products have been regulated at the national level for several decades, rather than by individual states. The only way you can label a product as organic is to be certified by a USDA-accredited certifier; but of course the rules don’t allow illegal substances to be receive the organic stamp. So there will be no such thing as USDA organic marijuana until the feds legalize the crop.

Naturally, there are no rules against growing weed organically, you just not supposed to label it as such. However, it seems many growers and dispensaries are openly flouting the USDA’s labelling rules – perform a Google search for “buy organic marijuana” and you’ll see what I mean – even though technically they could be fined by the USDA for doing so (apparently the agency has better things to do than enforce that particular rule).

Where Can I Get Organic Weed?

At least two companies are offering third-party certification for marijuana grown in a manner consistent with USDA organic standards, without actually calling it organic on the label – Certified Kind and Clean Green. These are a great place to look for organic marijuana options near you. Clean Green lists 108 certified growers and 21 certified dispensaries in six of the nine states that have legalized recreational marijuana thus far.

What’s the difference between organic vs non-organic marijuana?

It’s not much different than the food you eat. The difference between locally grown organic vegetables and vegetables grown hundred of miles away without organic farming is very much the same as the weed you smoke.

In 2015 the state of Colorado had to destroy tons of cannabis multiple times because they tested too high in chemicals like pesticides. There’s no framework requiring growers of cannabis to adhere to an allowable chemicals regimen. Their biggest challenge is controlling things like spider mites and mildew.

I’ve worked in the wine industry for a while where the debate about organic vs. non-organic farming has been going on for years. There was a vineyard manager I spoke with you had a great quote. He said, “would you paint your baby’s crib with lead-based paint or latex paint? Before you answer, you should know lead-based paint would be considered ‘organic’ whereas latex would not.” The point being is just because something is “organic” doesn’t automatically mean it’s better. There are farmers who farm responsibly, maybe even “better” than organic but they don’t go after the certification.

Comparing wine to food or cannabis isn’t apples to apples, however. Wine grapes go through a production process including fermentation and laboratory adjustments. Food and cannabis come straight off the plant and go into your body. I would say it’s more important for the food and cannabis to truly be grown in the purest way possible. Controlling spider mites or mildew without harsh chemicals is possible, but as grow operations scale up it becomes more challenging.

Ultimately, for legalization to work it’s critical the feds do put some sort of benchmark in place. We’re talking about an industry that could grow to be $30B in 2020 (to put that into context, the NFL is a $12B business, and it took 50 years to build). There are so many products that use the plant material, consumers need a way to know what they’re putting into their body.

On a side note, nobody says “harshing their mellow” anymore.

Organic Marijuana: How And Why To Cultivate it

LET’S START AT THE BEGINNING: WHAT IS ORGANIC CANNABIS?

It is important to know that there is no official process for certifying cannabis as “organic”. Due to our beloved plant’s difficult legal landscape, it cannot be regulated by the same licensed bodies that accredit organic fruit and vegetables. Instead, we have to rely on understanding what growing organically means and applying the same principles to cannabis cultivation.

A general definition of growing organically is “to farm or cultivate in a way that supports natural, sustainable processes”. Thousands of years of natural cannabis cultivation have achieved just that. The plant would be grown outdoors, using the land and soil to supply nutrients. In turn, the cannabis plant would support its own natural ecosystem before being harvested. The process would then be repeated seasonally by growers.

It wasn’t until cannabis prohibition became widespread that growers were forced to head indoors. The result was, in most cases, a need to supplement natural routines with artificial ones. In this case, pesticides, chemicals and artificial lighting were used to speed up or enhance growth and production.

If we now refer back to our organic spectrum: If we grow indoors, but this time we use a natural produced growing medium without any pesticides, technically, those plants are being grown organically—at least to a degree. If you factor in the lights (artificial) and the cost of running an indoor grow, does your grow room still fall under the umbrella of sustainable?

Growing cannabis organically comes in many forms. Unfortunately, until marijuana can be sufficiently regulated, what constitutes as organic is up for debate. However, that doesn’t mean that growing organically is something you should disregard.

WILL YOU BENEFIT FROM GROWING ORGANICALLY AT HOME?

The benefits of growing produce organically come widely documented. Cannabis is no different, as you will be ingesting it. Whether that be literally, or by smoking/vaporising, marijuana and the components you used to grow it will be entering your body. By using pesticides and chemicals to enhance growth, you are running the risk of those compounds entering your body when the cannabis plant absorbs them.

The most exciting benefit is the improvement in flavour and aroma. Organic growing supports the natural production of cannabinoids and terpenes. Working together, these chemical compounds give cannabis its highly desirable aroma—and effects of course. With many strains sold on their flavour alone, anything that offers a boost is greatly received. All of the plant’s energy can be put into its development, rather than having its potential hindered by unnatural chemicals.

On a wider scale, your environmental footprint is also substantial, depending, of course, on how you grow cannabis. Electricity, heat, water; all of these elements can have an impact on the broader environment. Switching to an organic grow, indoors or out, can save you money, while supporting a natural ecosystem.

We will cover some easy to follow steps that all growers can take, if they want to grow cannabis organically. Before we do, let us consider the impact of growing organic cannabis on a commercial scale.

WHAT ARE THE IMPLICATIONS OF GROWING ORIGINALLY ON A COMMERCIAL SCALE?

Despite the challenge surrounding cannabis and its legality, business is still booming. The number of US states legalising the plant on a medicinal and recreational basis is steadily increasing. European nations are also slowly moving towards a greater acceptance of cannabis. The demand for weed is growing, which means we need more of it. Some estimations put the energy usage of commercial cannabis operations at more than that of hospitals of the same size. The environmental impact is significant.

The rapid rise in demand also puts commercial growers under more pressure to deliver. You cannot rush nature, so inadvertently pesticides and chemicals become an attractive option. Mainstream consumers are faced with the same risks as those growing artificially at home. Foreign substances can enter the body, and have the potential to cause harm.

Organically grown cannabis is better for the environment, safer for consumers, and stands a better chance of being accepted for future scientific studies. It supports the industry’s desire to become a trusted commodity, ensuring cannabis production can remain sustainable.

GROWING ORGANIC CANNABIS AT HOME REQUIRES SMALL CHANGES

We have talked in length about the benefits of growing cannabis organically. Although the drawbacks are minimal, there are still some disadvantages. Growing organically can take longer, and may cause yields to be smaller. The good news is, with proper research, the majority of drawbacks can be negated.

Organic growing is a sum of all its parts. It is essential to consider the entire picture before making a switch. Here is how you can take an organic approach to growing cannabis.

SOIL

Soil is the lifeblood of cannabis—organic soil centres on sustaining the perfect environment for microorganisms. If we focus on feeding them, they will naturally support the food web, and supply our cannabis plant with the vital nutrients it needs. To do this, you have two options. Creating your own super soil from scratch, or buying a ready-made organic soil. Assuming you want to do the former, you will need a few unique ingredients.

A mix of earthworm castings, bat guano, kelp meal, perlite, peat moss, pumice and fish emulsion is a good place to start. It may sound like a lot, but in reality each component is only added in small amounts. Several specific soil recipes can be found online for those keen to experiment.

Once your soil is prepared and your seedling planted, all you need do is water regularly. From this moment on, normal growing routines can be resumed.

LIGHT

A completely organic and sustainable environment would use natural light to fuel photosynthesis. If you live in a climate that can provide those requirements, moving your cannabis plants outdoors is the best way to grow organically. If you cannot, adjustments in the types of light you use can lessen your impact on the broader environment. Switching to LEDs is a perfect example of growing more sustainably. High quality LEDs can use up to 70% less electricity than a 1000W HPS light.

Thankfully, yields using LED lights have been improving. This is driven by both a better understanding from growers and an improvement in the quality of lights available. Some growers use a combination of LED and HPS lights. LEDs are most suitable for the vegetative stage, while HPS lights support bud production during the flowering stage. Ultimately the degree to which you grow organically comes down to personal preference. There is no denying that the money saved by LED grow lights is a welcomed bonus.

PEST CONTROL

Encouraging a natural ecosystem should discourage the majority of pests. Every element of organically grown cannabis supplies the next entity in the cycle. Organic matter provides the soil with nutrients, which feed the microorganisms and so on. Pests, however, can still occur and without the ability to use artificial pesticides, what are your options?

Companion planting is the best way to support the ecosystem you have created, while preventing pests from destroying all your hard work. Basil and dill will repel gnats, while marigolds are ideal for avoiding an aphids infestation. Just make sure you leave sufficient space between companion plants and your cannabis. You don’t want them to have to share nutrients.

There are some natural pesticides made using need oil, which you can also try. They have shown efficacy for the treatment of most common pests. The lesser-known Bacillus thuringiensis is also worth considering. It is useful in preventing fungus, mosquitoes and caterpillars.

THE FUTURE OF ORGANIC CANNABIS CULTIVATION

We have covered the principles that underpin organic growing alongside several tips for taking on the challenge yourself. While it is true that from a commercial perspective, there is not a verified accreditation for organic growing, the importance of doing so is significant. Not only is a more flavoursome product produced, but the weed is also free from potentially harmful substances.

Some independent institutes are being set up to certify commercial growers as organic. The hope remains that as the legality of cannabis increases, the same standards set by other areas of commercial growing can be applied to the marijuana industry. Growing organically supports the fundamental value of nature—something that is at the very heart of cannabis. Mother nature gave us marijuana, and it seems only right to give something back.

Vinegar Weed Killer: Grandma’sRecipe For Fast Weed Control

Do You Want A Vinegar Weed Killer Recipe?
Take Your Pick… Make Your Own… Or Think Twice?

Everyone has weeds. Many have heard that you can use vinegar as an herbicide to get rid of them. Is it true you wonder? How do you use it?
Yes, it is a fact that you can kill weeds with vinegar. That sounds great, doesn’t it! People hate to spend money for a product to get rid of weeds, and vinegar is cheap. Many people would like to avoid chemical sprays, and vinegar is all natural. Sounds like the best of both worlds.
Except….. there are a few exceptions, limitations, & details, that you should know about before you grab a bottle of vinegar off the shelf and seek revenge on those weeds.

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Facts About Vinegar And What It Can Do

Vinegar is a natural product, usually derived from grain, apples or grapes. It is distilled through a fermentation process. The vinegar you buy is typically labeled at 5% acidity. This means it contains 5% acetic acid, the active ingredient.
Acetic acid is what makes vinegar a weed killer. Actually, it makes vinegar a plant killer. Acetic acid, from any source, will kill most vegetation because it draws all the moisture out of the leaf.
It is fast. Spraying full strength vinegar on a plant in full sun will often result in a withered, brown plant in only a few hours, for sensitive weeds, or by the next day in tougher plants.
It is non-selective, meaning it might kill everything it touches. This limits the usefulness of a vinegar weed killer, to the extent that you are able to control over-spray that would get on desirable plants.
Do you have places where you could use these characteristics of a vinegar weed killer? If it seems like a good idea, how do you use it? That brings up an interesting development.

Somebody Changed Grandma’s Recipe!

We don’t know whose Grandma started it, or how. It may have been an accident when she tossed out a bad batch of apple cider! The idea has been around a long time. But through the years, there have been quite a few variations for making a vinegar weed killer.

Searching the internet and other sources for home made remedies comes up with a wide range of formulas that appear to have originated from one basic recipe. Look at this simple chart to see the range of suggestions you can find.

VINEGAR SALT SOAP WATER OTHER
1 gallon 1 cup 1 tbsp none none
1 gallon 1 cup 1 shot warm none
1 gallon 1 lb. 1 tbsp none none
1 gallon none 1 tsp none orange oil
4 cups ¼ cup 2 tsp none none
1 cup none ½ cup 2/3 quart none
2 parts none 1 part 2 parts none
1 tbsp none 1 tsp 1 gal, hot none
1 tbsp 1 tsp none 1 gal, hot 1 tbsp gin
1 oz. none 1 oz 1 quart 1 oz. gin
1 gallon none none none none
1 gallon none 1 oz none none

What do you think? Do you want to try them all?

The differences in concentration for each ingredient, and the combination of mixes, make you wonder! Are any of them a good idea?

If you would like to know exactly what these different ingredients do, you must read What To Expect From Home Made Weed Killer.
A few of the critical cautions mentioned will help you narrow down this list of recipes for vinegar weed killer.

Some of the combinations seemed too weak and probably wouldn’t work, while others were too wacky to even try. I decided to try the last two on the list, to find out what full strength vinegar as a weed killer could accomplish.

Sampling With Vinegar Weed Killer

I have plenty of weeds in one area of my yard that is not landscaped, so I did not have to worry about over-spray that might kill good plants.

I sprayed weeds (1) with full strength vinegar plus soap; (2) with full strength vinegar only; and (3) with soap and water only, just for comparison.
Here are my results:

Using Full Strength Vinegar And Soap

  • The soap added was dishwashing soap, 1 oz per gallon.
  • The weeds were affected the fastest and most completely with full strength vinegar and soap, compared to the two other groups.
  • Weeds in full sun for several hours died faster than weeds that were in shade an hour after spraying. This reflects how the plant requires more moisture in the sun.
  • All the weeds appeared completely dead 24 hours later.
  • About half of the broadleaf weeds died completely, including young dandelions. (No older dandelions, which have a large taproot, were sprayed.) One week after spraying, the other weeds were showing new growth. (As an example, see the photo of oxalis below on left.)
  • Three days after spraying, crabgrass weeds were showing new growth appearing from the base of the plant, and about 60-70% of them recovered. The younger crabgrass plants were more likely to die. (Photo on right, crabgrass one week after spraying.)
  • A patch of Bermuda grass under one area of heavy weeds turned brown, but eventually recovered.

Oxalis, a broadleaf weed, starts to re-grow one week after being sprayed with a vinegar weed killer.

Crabgrass also starting to regrow quickly, at about 5 days after being sprayed with vinegar.

Using Only Full Strength Vinegar As A Weed Killer

  • The vinegar spray without the soap was not as effective as vinegar with soap. It was even obvious while spraying that the plain vinegar was not readily staying on the leaves of the weeds, especially not on crabgrass.
  • Not as many of the broadleaf weeds died, and all were slower to show symptoms. Those that survived were quicker to recover. Control was about half compared to the spray with soap.
  • The crabgrass also recovered more quickly than in the first batch.

Soap And Water Only

  • Dishwashing soap was used at 2 oz per gallon.
  • The soapy water alone had no apparent impact at that concentration on weeds or grass.
  • The soap aids the effectiveness of the vinegar but does nothing on its own (at that rate).

I used a small sprayer, 1 ½ quart size, that pumps up pressure. This puts out a smaller, softer spray pattern than my larger tank sprayer. It allowed me to confine the spray to the desired area much better.

I also sprayed some weeds in ground cover and had a little bit of overspray. The ground cover died where it was hit, but it is the spreading kind and has filled back in.

The conclusion appears to be that a vinegar weed killer can be effective on some weeds, in some situations. However, consider the following information before you decide to try it.

More Facts About Using A Vinegar Weed Killer

Vinegar won’t move through the plant to kill the root, like some chemical sprays will do. The root may die anyway, depending on the variety of weed, and how mature it is. Young weeds may not have sufficient reserves to put out new growth. The older weeds that grow back would be weaker, and many should die with a repeat application of the vinegar weed killer.

Some plants are not as susceptible to vinegar. A waxy coating or a “hairy” (fuzzy) surface may interfere with the absorption of the vinegar. This is the type that would suffer more by adding the soap to a vinegar weed killer recipe.

Vinegar applied to the soil as a full strength drench could kill the root directly. This is not recommended, since roots from good plants could also be affected. Also, the effects on soil microorganisms is unclear. They might die, or move out of the area, or become inactive temporarily. This would reduce soil fertility.

Vinegar would lower the pH of the soil, making it more acidic. This could be good if your soil is alkaline, not so good if it is already acidic. Yet, it is unlikely that the small amount used would cause much variation.

(EDITORIAL NOTE: If you have a large area to spray, and would prefer to avoid multiple applications, an alternative would be Round-up, or the generic alternatives. It can kill root and all in one spraying. Like the vinegar weed killer, it is non-selective.
Yes, this is a chemical spray. I mention it because some of you may find it acceptable. There is strong commentary by both advocates and critics regarding the safety of this product. Glyphosate is the active ingredient and may not be as bad as some other chemicals, in terms of lingering in the soil.

But everyone should evaluate where can you personally make some contribution to lessening your stressful impact on the environment. This may be one of those situations where if you decide to use it this time, you also commit to a more proactive approach next time.)

Disclaimer

Anyone desiring to use a vinegar weed killer should be aware that the results they get will be quite unpredictable. It would be wise to try sampling before using any formula on a broad scale.

Vinegar weed killer can be found in a few products made by garden suppliers, but they have to meet certain regulatory guidelines before they can recommend using vinegar as an herbicide. This is for consumer protection.

Don’t blindly accept the recommendation of anyone on the internet, or other sources, saying vinegar weed killer is safe, natural and effective.
It might be in some situations, but not in others, it all depends. There are so many variables.
Use your best judgment. You’ve learned here the basic factors that should help you decide if it is a good idea to use a vinegar weed killer in your situation.

Update & Caution: Using Stronger Vinegar

A number of sources on the internet have begun to suggest the use of a stronger version of this homemade weed formula, usually in blogs and forums. Is this a good idea?

Gardeners have contacted me inquiring about finding and using a more concentrated vinegar weed killer. It is possible to obtain vinegar in a 10% or 20% concentration, though these are not commonly found at domestic retail outlets.

Caution: be extremely careful if you intend to use this harsh product. The fact that it is still called vinegar can lull you into a misguided complacency, thinking it is a mild, natural solvent.
Remember, this is an acid, and you need to treat it with respect, the same as with other caustic substances like pool cleaners.

OUCH! Caution Repeated: I was quite careful while handling the product, until the very end after cleaning up. Unknowingly, I had spilled over the edge of the bottle and got some of the full strength liquid on one hand.
Very quickly I started feeling a burning sensation. I immediately rinsed off the acid, but the damage was done. My skin had burn marks on the affected area, as if I had grabbed a hot bar-b-que grill.

I tried the 20% acetic acid and found the results favorable at killing some of the weeds which were resistant to the common formula mentioned above. These were larger, more mature weeds, of different varieties. They responded quite quickly to the spray and did not grow back.

Noteworthy is that it was an extremely hot day, which contributed to the impact of being a desiccant to thoroughly dehydrate the weed.
Also realize that the stage of growth can affect a plant’s regenerative properties. These weeds were already forming seed-heads. Sometimes when a plant has invested its energy into forming seeds, it is unable to recuperate after being harmed. This varies from species to species, so your results may vary.

Wear a good quality nitrile glove or some type that is resistant to chemicals — and be careful. It would also be smart to wear safety goggles and a mask to interrupt any vapors. This may seem silly to some of you macho types, but you never know when something might splash, plus some people will be more sensitive than others.

If you are of a mindset to take this approach and try the stronger vinegar solution, here are a few on-line suppliers for the 20% acetic acid product sold in one gallon containers, each found on Amazon.

The pic on the right may be the best price, except for the full case price below:
Bradfield Horticultural Vinegar
OR 20% Vinegar – Generic Brand
OR Vinegar 20% Gallon size in case of 4.

Note that this is typically used at full strength, unlike the concentrated version of chemical lawn and garden products that are diluted with water before spraying.

If you dilute the 20% acetic acid you end up with the less potent product like the grocery store variety. The strong solution is too expensive with shipping to plan to dilute it.

Also note that the coverage of a one gallon bottle at full strength is going to be limited. Most common garden sprayers will cover at most 1,000 sq. ft. with a gallon of liquid, so consider that into the overall cost of your project before you go this route.

Commercial Vinegar Weed Killer?

As a final note, quite a bit of testing is being done on natural alternatives to the chemical nightmare. Based on that research, the usefulness of vinegar as a weed killer is being better understood.

Finding the best way to utilize that knowledge is the next step, and a number of companies have jumped through the required hoops and brought to market a fast acting weed and grass killer that uses the high octane version of this ingredient.

These commercial products frequently add various additional ingredients, like citrus oil or clove oil, with the expectation that the mixture will make it work faster, or broaden the effectiveness to kill a wider range of weeds, or make the damage more permanent.

It may accomplish that, or it may simply set apart one product from another for marketing purposes. I plan to have some comparative testing done on several of these products later this spring. Check back later for an update to this update.

Other active ingredients are being promoted as well, such as concentrated citrus oil, or ammoniated salts of fatty acid. I’ll investigate these as well in the future.

What To Expect From A Home Made Weed Killer.

Chemical Weed Killers.

Lawn Weeds general info page.

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Organic Herbicides – Do They Work?

by W. Thomas Lanini

In recent years, several organic herbicide products have appeared on the market. These include Weed Pharm (20% acetic acid), C-Cide (5% citric acid), GreenMatch (55% d-limonene), Matratec (50% clove oil), WeedZap (45% clove oil + 45% cinnamon oil) and GreenMatch EX (50% lemongrass oil). These organic products can be effective in controlling weeds, but there are limitations. In this article, I will summarize the information that we have learned from trials on the efficacy of these herbicides and economic considerations for commercial use. Although these products are of interest for use in sustainable production systems, organic growers should always check with their organic certifier in advance of the intended application as such use of the alternative herbicide may not be cleared by all agencies.

Weed Control and Selectivity

Organic herbicides kill weeds that have emerged but have no residual activity on those emerging subsequently. Further, while these herbicides can burn back the tops of perennial weeds, perennial weeds recover quickly.

These organic products are effective in controlling weeds when the weeds are small but are less effective on older plants. In a recent study, we found that weeds in the cotyledon or first true leaf stage were much easier to control than older weeds (tables 1 and 2). The control ranged from better than 60% to 100% if these weeds received high volumes of these materials when they were just 12 days old. When broadleaf weeds were 26 days old, even high volumes of these materials gave at best less than 40% control.

We also found that broadleaf weeds were easier to control than grassy weeds — the best control on even young, 12-day-old grass weeds was only around 40 percent. This may possibly be due to the location of the growing point (at or below the soil surface for grasses) or the orientation of the leaves (horizontal for most broadleaf weeds).

All of these materials are contact-type herbicides and will damage any green vegetation they contact. However, they are safe as directed sprays against woody stems and trunks. For turfgrass sod production, organic herbicides could be applied when preparing the seedbed and then again with the first flush of weeds. Grass seed could be planted a bit deeper (1/4 to 1/2 inch deeper) to delay turfgrass emergence, so that the organic herbicide could control the broadleaf flush without adversely affecting the turfgrass.

Application

Organic herbicides kill only contacted tissue so good spray coverage is essential. For example, a large, flat nozzle (e.g. 8006) would be preferable in turfgrass production. In tests comparing various spray volumes and product concentrations, high concentrations at low spray volumes (20% concentration in 35 gallons per acre) were less effective than lower concentrations at high spray volumes (10% concentration in 70 gallons per acre). Because organic herbicides lack residual activity, repeat applications will be needed to control new flushes of weeds.

In addition to high volume, we found that adding an organically acceptable adjuvant resulted in improved control. Among the organic adjuvants tested thus far, Natural wet, Nu Film P, Nu Film 17 and Silwet ECO spreader have performed well. Although the recommended rate of these adjuvants is 0.25 % volume per volume (v/v), increasing the adjuvant concentration up to 1% v/v often leads to improved weed control, possibly due to better coverage. Work continues in this area, as manufacturers continue to develop more organic adjuvants.

Environmental Conditions

Optimum environmental conditions are required when applying these organic products for good control of weeds. Temperature and sunlight have both been suggested as factors affecting organic herbicide efficacy.

In several field studies, we observed that organic herbicides work better when temperatures are above 75° F, so applications in the winter may be less effective than summer applications. However, recent experiments have assessed winter weed control during cool conditions (table 3), and in spite of cold temperatures, plantain control was very good with Weed Pharm, or the high rates of Weed Zap or Biolink. Annual bluegrass control was also good with these same materials during cool conditions.

Sunlight has also been suggested as an important factor, and anecdotal reports indicate that control is better in full sunlight. However, in a greenhouse test using shade cloth to block 70% of the light, we found that weed control with WeedZap improved in shaded conditions (table 4). The greenhouse temperature was around 80° F, so it may be that sunlight is less of a factor under warm temperatures.

Economic Considerations

Organic herbicides all work if you have enough volume and concentration to directly contact the weeds. However, these herbicides are expensive and may not be affordable for commercial crop production at this time. Cost in 2010 was about $400 to $600 an acre for broadcast application, which may be considerably more expensive than hand weeding. Moreover, because these materials lack residual activity, repeat applications will be needed to control perennial weeds or new flushes of weed seedlings. We see these herbicides eventually being used commercially with camera-based precision applicators that “see” weeds and deliver herbicides only to the weeds, not to the crop or bare ground.

W. Thomas Lanini is Cooperative Extension Weed Ecologist, Department of Plant Sciences, UC Davis.

Are There Alternatives to Glyphosate for Weed Control in Landscapes?

Controlling Seedling Annual Broadleaf Weeds Without Glyphosate

Skip to Controlling Seedling Annual Broadleaf Weeds Without Glyphosate

Many options are available to control small broadleaf weeds. The best alternative is to prevent the weeds from emerging by using mulches and sanitation practices that prevent the introduction and spread of weed seeds. Preemergence herbicides may be used to control annual grasses and small-seeded broadleaf weeds. However, even in the best-managed landscapes, some weeds will germinate and establish. These weeds will need to be controlled, manually or with postemergence herbicides, before they go to seed.

Manual removal

There will always be some hand weeding in landscape plantings. Remove weeds before they have a chance to establish a large root system and before they go to seed. This is best accomplished with frequent weeding – about every 2 weeks. Hand weeding frequently is effective for annual weeds but can also control perennial weeds before they become well established. The limitations, of course, include the expense and availability of labor to do so.

Flame, steam or hot-foam weeding

Heat can kill seedling broadleaf weeds. Flame weeding is effective on seedling broadleaf weeds growing in hardscapes but should not be used in areas where flammable mulching materials are present. Sites where flame weeding may be practical include cracks in driveways, between pavers, or in gravel mulch. When using a flame weeder you do not need to actually burn the weeds. A brief exposure to the flame will heat the water inside the plant without flames. The leaf tissues will collapse very rapidly after treatment. Larger weeds will require repeated treatments. Flame weeding will provide only foliar damage to grasses, perennial sedges and perennial broadleaf weeds. These types of weeds re-grow rapidly following treatment.

Where flammable materials are present, steam or hot foam weeding are preferred over flame weeding. The effect is similar to that of flaming. Commercial equipment is available that use pressurized steam (e.g. WeedTechnics™) or hot water + foaming agent (e.g. FoamStream, Weedingtech™). These machines remove the hazard of fire but do use about 60 gal of water per hour of use. Also, the output from these devices is HOT and accidental contact with the foam or steam can cause severe burns.

Postemergence herbicide alternatives

Several other non-selective herbicides are available for use in landscape plantings. These include: Diquat (Reward™), pelargonic acid (Scythe™), glufosinate (Finale™ and others), and many “natural products” such as vinegar and botanical oils. All of these products have contact-type activity. That means they do not translocate to the roots of treated plants. If applied at the labeled dose and with thorough spray coverage, each of these herbicides will control seedling annual broadleaf weeds. None of these products have residual activity (i.e.: no root uptake and no preemergence weed control) in soils.

Glufosinate (Finale™, Bayer Corp.) is a non-selective, postemergence herbicide that is sometimes described to be a contact action but is “locally systemic” – meaning it moves within treated foliage but does not translocate throughout the plant. Thus, Finale typically does not control perennial weeds (such as: bindweed, goldenrod, bermudagrass, and mugwort) as well as glyphosate. Yet, reduced translocation of Finale may offer advantages over glyphosate in some trim and edge applications and in landscape beds where one may avoid systemic damage to landscape ornamentals from inadvertent spray drift. Like the other postemergence herbicides described above, glufosinate has little or no potential for root uptake when applied to the soil.

Diquat (Reward™, Syngenta Corp. or Diquat SPC™, Nufarm Ltd.) is a postemergence, contact weed killer. It kills small annual weeds. Large annual weeds and perennials will be injured but not killed. Thorough spray coverage is necessary to achieve optimum results. In our research Reward herbicide was more effective when applied in spray volumes of at least 2 gal per 1,000 ft2 (over 80 gallons per acre). Advantages of Reward include rapid kill of small seedling weeds and relatively low cost. Compared to the other contact herbicides described in this section, diquat is more effective on young seedling grasses. Also, small amounts of spray drift will cause only cosmetic damage to landscape plants and will not translocate to kill desirable plants. Additionally, Reward is not as temperature sensitive as many other herbicides, working well in cool and warm weather. Disadvantages of this herbicide are lack of control of perennial weeds, grasses, or well-established annual weeds

Pelargonic acid (Scythe™, Gowan Co.) is also a postemergence, contact herbicide that controls small seedling broadleaf weeds but only injures larger annual weeds and perennials. In cold weather, Scythe is not as effective as Reward, but in warm weather Scythe provides very rapid weed control. Advantages of Scythe include very rapid symptom development (tissues show symptoms in less than 30 minutes), and Scythe™ is perceived by many people to be an alternative to traditional herbicides. Customers who do not wish to have pesticides applied to their properties will sometimes accept the use of soaps (such as insecticidal soaps) and may accept the use of Scythe, often considered to be a “herbicidal soap.” However, users should know that Scythe is not a certified “organic” option. Similar herbicidal soaps are available which are organic certified. As with Reward, spray drift on desirable plants will cause cosmetic damage but will not translocate to kill the entire plant. In all applications, avoid contact with desirable vegetation. The main disadvantages for Scythe are higher cost and it is somewhat less effective than Reward on larger weed seedlings. Additionally, the odor is persistent and offensive to some people, and spray drift can be a severe eye irritant.

Several OMRI-certified nonselective, contact-action herbicides are available in the marketplace; some of the more commonly-used products are described below and summarized in Table 1. These products generally contain one or more of the following ingredients: fatty acids, acetic acid (vinegar), or natural plant oils. Ammonium nonanoate (Axxe™) is an OMRI certified formulation of pelargonic acid, the same active ingredient as Scythe. Its performance is understandably nearly identical to that of Scythe. FinalSan™ is a mixture of fatty acid soaps with similar contact-activity. Suppress™ is an emulsifiable concentrate of two short chain fatty acids (caprylic and capric acid). These products are fast acting, contact-action herbicides destroying the integrity of the leaf surface and cell walls. They work in the same way that Scythe™ (pelargonic acid) does. But unlike Scythe, Suppress, Axxe and FinalSan have been approved by OMRI for use in organic agriculture and horticultural operations, including in and around landscapes. Suppress is less active when the carrier water pH is greater than 6.0. If water used to dilute the spray has a pH higher than 6.0, the addition of an acidifier like Biolink™ to the dilution water before mixing will improve product efficacy.

Many product formulations containing acetic acid (vinegar) and various botanical oils are available through commercial and retail distributors. These products are non-selective and have contact action similar to fatty acid herbicides. They are effective on seedling annual broadleaf weeds but only burn the foliage of perennial weeds, large annual weeds and grasses. Complete spray coverage is important to obtain optimum results. Symptoms are rapidly visible – within an hour on a sunny, warm day. Users should remember that “natural” does not always mean “safe”. Most products containing vinegar and natural oils have higher dermal toxicity than synthetic herbicides and may carry a “Danger” signal word on the label (Table 1). When using these natural products, avoid contact with skin or eyes, and avoid inhaling spray fines.

Contact-action herbicides, including OMRI-certified products, can be effective post emergence tools for small annual broadleaf weeds. They are less effective on grasses and sedges and, at best, will only knock down the top growth of perennial weeds. Still, with regular repeat applications, these products can be useful postemergence tools.

Steam Weed Control

C. Wilen CC BY – 4.0

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Steam Weed Control

C. Wilen CC BY – 4.0

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