How to kill wintergrass?

Kill Winter Grass in Buffalo Lawns

Winter Grass is another ugly and unsightly weed in Buffalo grass as well as all other lawn types. It’s bright green leaves and clumping characteristics can quickly overtake a lawn, transforming what would otherwise be a beautiful lawn into a complete mess of weeds.

Winter Grass will begin germinating underground in May, and will start emerging from the soil and in our lawns in late May and June. Winter Grass will continue to germinate, grow stronger, start clumping, and spreading as the winter months continue into July.

By the time August and September roll around, Winter Grass is in full growth, easily outgrowing the Buffalo lawn and sitting above it in stark contrast to the lawn around it. This is also the time that Winter Grass will begin going into full seed, making the weed even uglier.

This same seeding will be planting-out thousands of new Winter Grass seeds into your turf for emergence the following year. So if you have Winter Grass this year, it will be worse next year, worse the year after, and so it continues.

Therefore any Winter Grass in your Buffalo lawn must be treated as soon as possible.

Killing Winter Grass in Buffalo Lawn

Winter Grass is actually a very easy weed to kill, but only if it’s done at the right time.

Winter Grass Weed Killer is diluted with water in a watering can or spraying bottle as per manufacturer’s guidelines, and applied to the entire lawn, not just to the area which appears most affected.

Be sure to measure the lawn before treatment to ensure the correct dosage is applied. Once the Winter Grass Killer is applied to the turf, the lawn is then lightly watered, which filtrates the poison down to the roots of the Winter Grass where it does its work. You should then begin seeing the Winter Grass die off within 2 weeks.

When to Kill Winter Grass

Winter Grass must be treated at the right time of the year, otherwise the herbicide will have no effect whatsoever in killing the weed. We have explained that Winter Grass begins germinating underground in May, and that Winter Grass Killer acts on the root of the weed, also underground.

With this in mind, Winter Grass is best and most easily killed in May, pre-emergent and before we can even see the weed. You may still kill Winter Grass into June and sometimes July. However, the later we go into winter, the more mature the Winter Grass becomes and the more difficult it is to kill.

Treatments done as late as July may not even have a good effect, while Winter Grass treatments in August or September simply will not work – the weed is just too strong and will easily outcompete the herbicide.

A Plan to Kill Winter Grass

So the questions are … how can we kill Winter Grass before we can even see it in our Buffalo lawn, and what should we do if it is too late in the season to apply the herbicide?

If we missed the window to kill Winter Grass in May, June and possibly July, then do not attempt treatments, it will only waste your money. Mark down MAY in your diary for the next year to kill the Winter Grass. Because if you had Winter Grass in your Buffalo lawn this year, it’s a guarantee it will be worse next year, and so it must be planned for and treated properly.

Once the Winter Grass begins to go into massive seeding towards the end of winter, the best thing you can do is to mow the lawn with a rotary mower and catch the clippings.

A rotary mower uses a sucking action to pull clippings off the turf and into the catcher, and will thus do the same for many, but not all Winter Grass seeds. So you are actually making the problem a little less worse for next year.

Mow more regularly when necessary to ensure that no Winter Grass is left to seed for too long between mowings, otherwise you’ll be allowing more seeds to fall back into the lawn for more weeds next year. Once the catcher is full, be sure to empty into the garden bin and not into the garden bed. You don’t want to be moving the Winter Grass problem from your Buffalo lawn and into your garden beds.

Multiple Winter Grass Treatments

You will notice that not all the Winter Grass will die in the Buffalo lawn after a single treatment of Winter Grass Weed Killer.

If this is the case then a second treatment can be undertaken after 3 to 4 weeks, as long as you are still in the safe time period for killing Winter Grass – which is best between May and June, but can also have a good effect in July.

You will also notice that even if you had success in killing Winter Grass this year, it will still emerge next year, and the year after. This is because not all weed seeds will germinate in a single year. Instead they will stagger their emergence over several years as this gives the weeds their greatest chance for survival. Therefore be aware of this fact, and give another simple Winter Grass treatment in the following years if necessary.

As their name suggests, pre-emergent herbicides are applied before weeds emerge. In the case of poa annua, that means applying a pre-emergent herbicide like Dimension 2EW, Hi-Yield Weed and Grass Stopper, Barricade 4FL, or another pre-emergent labeled for poa annua on your lawn before poa annua seeds begin to germinate.

Read the label of any pre-emergent you may consider using to be sure it is compatible with the type of lawn you have. Not all pre-emergents can be used on all grass types.

Apply in the fall before the first frost occurs, before the soil temperature reaches 70 degrees or below. If you live in an area that does not have frost, you would apply before temperatures drop. The timing of your application depends on where you live. Consult our lawn care calendars to determine when to apply your pre-emergent herbicide treatment.

It is advised that you do two fall pre-emergent herbicide treatments, spaced 30 days apart from one another. This will help ensure your entire lawn is treated, reducing the number of spots you might miss with one treatment. It will also increase the amount of time the pre-emergent treatment will last.

You will also need to apply a spring pre-emergent herbicide treatment sometime between late January and early May, before temperatures rise and weeds begin to germinate. Again, consult our seasonal calendars or contact your local extension office for timing advice.

Watch the video below to learn how to apply a pre-emergent herbicide.

Species category: Grasses

Scientific name: Poa annua

Winter Grass – What is it?

Winter Grass is a low growing turf grass. It appears as a bunch or can be a slightly spreading, winter annual weed. Some subspecies exist that are short-lived perennials which are particularly evident in bentgrass golf greens.
Winter grass is widespread throughout Australia and is a significant weed problem in many situations.
It has a pale green colour with smooth leaves that are finished in a blunt point. The leaves are often soft and drooping and Winter Grass can reach 20-30cm.

When does Winter Grass occur?

Winter grass requires a significant amount of light to germinate, and the optimum temperature range is from 10 to 16°C. The common Winter Grass name derives from its preference for cooler temperate climates in Australia.

It can establish itself at any time during the year but is particularly prevalent in winter and spring.

What damage or effect will Winter Grass have?

Despite its weed categorisation, some varieties can commonly be found on many putting greens.
It is a very common weed in lawns and gardens, and is widespread. Poa annua is characterised by its prolific seed production which makes it a challenge to control. The seeds rapidly germinate and it will grow very aggressively.
On turf, it can be aesthetically displeasing but also cause patches and disrupt the quality of the playing field.


Preparing to overseed your summer bermudagrass with ryegrass for a winter lawn? You’re way too early. That’s just one of the warnings offered by turfgrass researchers at the University of Arizona’s Maricopa County Cooperative Extension program. Overseeding now could leave large bare patches in your Bermuda lawn next summer. Avoid these three common mistakes for a prettier, even lawn all year that requires less work, money, and water.

1. Timing: When you begin to water winter seed, your bermudagrass growth should be slowing down. If it is still hot – as it is in late September – the heat and water will encourage Bermuda to grow again, exhausting the food it should be storing for next spring. That means a starved and patchy lawn next summer. Don’t overseed until mid-October.

2. Scalping: There is a long-held belief that it is best to dethatch Bermuda and then mow and “scalp” the lawn to nearly bare ground before seeding for the winter. This is a myth. Scalping can remove many of the bermudagrass crowns above ground that the root system feeds to resume growing properly in the spring. Once again, that can lead to large bare patches in a summer Bermuda lawn.

3. Fertilizing: It is a waste of time and money to create a layer of manure when overseeding bermudagrass with winter seed. A light dusting of mulch can help to retain some moisture. Simply drag a grass rake over the winter seed to make sure it is in direct contact with the soil or use a reel mower (the type your grandfather used) to grind the seeds into the soil.

The Cooperative Extension has a short and clearly written set of instructions for overseeding bermudagrass with winter grass seed. Here are some of the basics.

Watering for ryegrass seed germination always takes a tremendous amount of water.

1. Preparing: Stop fertilizing your bermudagrass 30 days before you plan to spread your winter grass seed. Two weeks before overseeding raise the height of your typical mowing blades by 30-40 percent and decrease watering by 30 percent.

2. Seeding: Stop watering two to three days before seeding. Lower the mowing height another 25-30 percent, remove the collection bag and leave the clippings as mulch for the winter seed. Use 12 to 15 pounds of winter grass seed for every 1,000 square feet of lawn.

3. Nurturing: Water three to four times a day just enough to keep the seeds moist. Don’t let the water pool or run off the site. Overwatering can make seedlings prone to disease. Once you see the green haze of a new lawn cut water to once a day and then every other day. Slowly lessen the amount of water used on the new lawn over the next three to four weeks. Then you can use Arizona Meteorological Network Turf Reports for precise lawn watering instructions. Fertilize with ammonium phosphate two weeks after seedlings emerge and water the new lawn after applying the fertilizer. Mow when the grass is about three inches high.

A small area of lawn watered appropriately is an acceptable part of a desert landscape. It cools the yard, offers a place for dogs and children to play, and it’s attractive. Wall-to-wall turf is a waste of water in a desert urban center. Check with your city if you are thinking about decreasing the amount of grass in your yard. Some AMWUA cities offer rebates to encourage you to replace grass with desert trees, shrubs, and groundcover.

Note from Water – Use It Wisely: If you do overseed, these steps will ensure that your winter grass is healthy and beautiful. But there is something else to consider. Do you need to overseed? Here are 10 reasons that might convince you to skip that winter lawn.

Did you know that up to 70 percent of water use is outdoors? That’s why we love desert plants and feature them each month. You can learn more about Ryegrass and other plants on our Arizona Low-Water-Use Plants page. Visit our page on Choosing and Planting Low Water-Use Plants for tips on plant selection and how to plant properly. Also, be sure to read through all of our featured Plant of the Month blogs!

This article was originally published on September 4, 2017, and is being reprinted with permission. Warren Tenney is the executive director of AMWUA (Arizona Municipal Water Users Association), one of 20 Water – Use It Wisely partners to offer water-saving advice and programs.

What is Winter Grass?

If you have an infestation of Winter Grass or Poa as it is also called, you’ll definitely want to know how to treat it. Winter Grass is the kind of weed, that if left uncontrolled can spread like wild fire before you know it. Here is some helpful information on what Winter Grass is and how to control this nasty weed in your lawn.

What is Winter grass?
Winter Grass, or Poa Annua is a low growing thin bladed grass. It has soft, drooping leaves grown in tutfs with triangular shaped seed heads. Winter Grass in wide spread throughout many Melbourne suburbs and is most common during the cooler months of the year.

When does Winter grass appear?
Winter grass as its name states is a grass which is most common during the cooler months of the year in Melbourne. It begins to germinate in your soil in May. You will begin to see it emerging around late May/ June and it will continue to spread thru your lawn over the cooler months. This is more damaging in lawn varieties such as Sir Walter DNA certified Buffalo, Eureka Premium Kikuyu VG and Sir Grange as they will be dominant during this time so therefore reducing their ability to out crowd the Winter Grass.

How do I get rid of Winter grass?
The best method to prevent Winter Grass is using a pre-emergent product such as Lawn Solutions Oxafert. This will prevent the Winter Grass from ever geminating in the first place. However, if you find yourself in the position where you have Winter Grass in your lawn before you get onto Oxafert, then we recommend a weed control “Winter Grass Killer”. This can be used to spot spray the Winter Grass, it is also recommended you do an application of Oxafert every 3 months on your lawn. Winter Grass can be a stubborn weed so may take one or two seasons to fully eradicate from your garden.

If you have any questions about controlling Winter Grass in your lawn or any other lawn questions please contact our friendly staff on (03) 9730 1128 or email [email protected]

Download our Wintergrass Blog HERE

Spring is just around the corner. Before long you’ll be sowing grass seed, applying fertilizer, and mowing the lawn! To return your lawn to a thick, healthy state, March is the time to begin controlling pesky winter weeds currently taking over your lawn, and preventing summer weeds.

Winter weeds include chickweed, bittercress, henbit and deadnettle, as well as perennial weeds, such as clover, dandelion and wild violets. These winter weeds actually germinate in late September and early October, but they often go unnoticed in the fall when they’re just young seedlings. They overwinter as a small rosette, and come spring they are ready to strike with a vengeance!

Winter weeds typically flower in March, but can start blooming in February if temperatures are warm! Regardless of when they bloom, you can stop them dead in their tracks with the right control product.

Products to Control Winter Weeds

At Merrifield Garden Center, our favorites to control winter weeds are:

Weed Beater, Weed B Gon, Speed Zone.

These control products come in liquid form, in both a ready-to-use spray and a concentrate that can be mixed with water through a tank-type or hose-end sprayer. Generally speaking, liquid weed killers are ideal for controlling actively growing weeds because they typically provide better surface area coverage than granular products. Plus, since they are applied as a spray, they can be turned on or off as needed, limiting waste or overuse.

We really like Speed Zone as it contains the same three active ingredients as the other products, but also has Carfentrazone, which makes it work faster and be effective at lower temperatures (50 degrees, versus 60 degrees). Speed Zone also has a two-week waiting period before reseeding the lawn, compared to the three-week waiting period that most of the other products require. This allows you to get started on your overseeding project sooner so that you will be growing thick and healthy turf.

Most winter annuals can be controlled with just one application of weed killer. However, because perennial weeds live year-to-year with an established root system, some of them may be more difficult to control than others. Clover, for example, can typically be controlled with just one application, while others, such as wild violet, may take several applications to effectively control.

Regardless of the weed control product you use, none of them will hurt your lawn if they’re used as directed. Be sure to treat any existing broadleaf weeds in the lawn now, so that you’ll be ready to start building a beautiful new lawn from a clean slate.

Winter Annual Lawn Weeds

Struggling with lawn weeds? You are not alone. On this page you will find useful information on several winter annual weeds and control methods.

To assist you in your lawn weed id, you will also find weed names, photos, the conditions that promote that weed’s growth and how to control them. Some weeds can be controlled without herbicides, while for others, control will be more difficult without using them.

An “annual” is defined as a plant that germinates from seed, grows to maturity, produces seed and dies within a 12 month period. However, most annuals only live for half a year at best, with a few exceptions.

Annual weeds will either be “summer annuals” and “winter annuals”. This page is for winter annual lawn weeds. Most winter annuals will germinate in late summer or fall, survive through the winter and grow quickly in the spring. The will produce seed and die by late spring or early summer.

Since annuals die each year, they must come back the following year from seed. To ensure their survival, most annual lawn weeds produce an enormous amount of seed. Some plants can produce several hundred thousand seeds each year. They are quite successful since annual weeds are some of the most abundant weeds on earth.

Most lawn weeds don’t like competition, so a thick lawn turf is your greatest defense against weeds. Focusing attention on weed control without building a thick turf is a guarantee you will have continued weed problems. For lawns in poor condition, it may take a couple of years om improvement before you see a major reduction in lawn weeds.

The lawn weeds listed on this weed identification page are not an exhaustive list and you may have other lawn weeds common to your geographical area. Be sure to check with your local university extension office for specific conditions in your area.

Important notice: A mention of any herbicide on this website is not an endorsement, but is only a list of commonly used and effective products. Herbicides should be used as a last resort. Remember, that herbicides can be dangerous, so be sure to read the entire label before using.

Please note that different states, or even regions within states, may have specific laws pertaining to herbicide use or specific products. Your local university extension office can be a great help in determining what products are available and legal for you to use. Not all herbicides are available for homeowner use and the EPA is removing or adding herbicides frequently. Always use and store products according to instructions on the label.

Corn Speedwell

  • Winter annual with prostrate growth habit.
  • A dense matt forming weed of thin or poor quality turf.
  • Small rounded leaves no more than 1/2 inch in diameter.
  • Small blue to purple flowers about 10mm across.

Weed Identification

Corn speedwell is a spreading winter annual that germinates in the fall. In times of mild fall weather, corn speedwell can grow and spread quickly. It survives the winter and then grows considerably more by mid-spring.

This is a plant that is seen mostly in poor quality turf and doesn’t compete well with thick turfgrass. It is primarily a prostrate growing weed that forms dense mats. In lawns where corn speedwell has been a problem, any condition that would lower turf quality only benefits the weeds and becomes more invasive.

Look for a plant with leaves positioned opposite each other along the base. However, farther up the stem, the leaves are smaller and set alternately on the stem.

The flowers are a blue to purple color and very small, about 10mm across. The seed pods are heart shaped.

Cultural Practices

Speedwell can be a difficult plant to remove by mechanical means. The weed tends to break easily and leaving a lot behind.

In warm season grass, there is nothing to slow corn speedwell germination. By the time it germinates warm season grasses have gone or are going dormant. Thicker grasses such as zoysiagrass may only experience slight problems. In the spring, many warm season grasses can get very weedy until it breaks dormancy.

Building a thick healthy turf, whether in warm season grass or cool season grass, is the best way to discourage winter annual weed invasion.

Herbicide Use

You can use a preemergent in the fall to discourage seed germination. However, in warm season grass if you plan on overseeding, a preemergent will hinder your lawn seed from germinating as well.

The best time for post-emergent herbicide use is in the fall or early spring. Weeds are still young and growing making them easier to control. By mid-spring, the weeds have already hardened and are more tolerant of herbicides.

Use herbicides with 2,4-D, Dicamba, MCPP, or MCPA. A formulation with at least three of these ingredients will provide best control.

For a preemergent herbicide, use one with the active ingredient Pendimethalin. Others may also be labeled for corn speedwell.


  • One of the most common winter annuals.
  • Square stems.
  • Leaves positioned opposite each other on stem.
  • Slender, tubular, pink flowers at the tips of stems.
  • Spreads by seed.

Weed Identification

Henbit, sometimes confused with purple deadnettle, is a common winter annual with an upright growth habit. It grows in moist soils and can reach heights of 12 inches by mid-spring. One of the unique characteristics of this plant is its square stems.

The leaves are positioned opposite each other along the stem. They are rounded with rounded tooth edges and each set makes a circle (whorl) around the stem. There is a small space between each set of leaves so that a small amount of stem is clearly visible.

The flowers are slender and tubular shaped with two lips opposite each other on the flower’s top. The flowers are pink to purple and can be ½ to ¾ inches long. The flowers arise from between the leaf whorls on the tip of the stems.

Cultural Practices

Henbit, like many winter annuals, does not compete well with thick turf. It prefers thin or poor quality turf best. Dormant warm season grass may have a problem with henbit in the spring. However, in newly seeded lawns, henbit can be a major problem weed. In small patches, pulling may offer some relief. Henbit can survive until May and then dies back until germination in the fall.

Herbicide Use

Herbicides need to be applied in early spring. Using a formulation designed for the cooler temperatures in spring is desirable. In late spring the plants have harden being near the end of their life, so they will be less susceptible to herbicides.

As a basic rule, similar lawn weeds can usually be controlled by the same herbicide mixture. This is also true with the two lawn weeds, henbit and the similar looking plant, purple deadnettle. (in photo on left

Using a 3 or 4 way herbicide formulation (3 or 4 herbicides mixed together) will provide best results. Using 2,4-D, Dicamba and MCPP will control henbit.

Common Chickweed

  • A winter annual that grows best in shaded areas.
  • Grows in mounds 5 to 7 inches tall.
  • Small white flowers with 5 deeply lobed petals.
  • Can be easily pulled up by hand.
  • Gets it name when it was used as a starter food for young chickens.

Weed Identification

Common Chickweed is a winter annual that prefers moist sites. It is common to see it growing in gardens, mulch beds under trees or on the shaded side of homes. It has a good cold tolerance and can survive temperatures near 0 degrees. It will bloom all winter even when temperatures dip several degrees below freezing.

It has a shallow root system making it easy to be pulled up by hand. The plant has weak stems that cannot stand well on their own. They must lean on other limbs to form a mound. The limbs that touch the soil will root at the nodes.

The mature leaves are approximately ½ inch long with a smooth texture. An interesting fact about the leaves is that they fold up around the stem at night.

The flowers grow in clusters on a long stalk starting from the leaf axils. There are five white petals on each flower. However, each petal is deeply lobed which gives it the look of ten petals.

Cultural Practices

Chickweed grows in moist, shaded soil. It is found on shaded hillsides, shady side of lawns, mulch placed under trees and related sites. It will grow in sunny areas as long as the temperature remains cool.

The primary way of preventing chickweed from establishing is to build a thick, vigorously growing lawn. Mowing your grass at its tallest recommended height will help as well. Taller mowing heights promote deeper rooting and strengthens grass. However, warm season grasses may experience problems with this and other lawn weeds until it breaks dormancy.

Herbicide Use

Several herbicides are labeled for control of common chickweed. Products containing 2,4-D plus Dicamba will control it. For its close relative mouseear chickweed, the same mixture will also work well. Using a formulation of at least three herbicides will give better control and also help control other lawn weeds in your lawn.

A preemergent can be applied in the fall before seeds germinate. If you are planning to overseed your lawn, you shouldn’t use a preemergent. If you do, your grass seeds won’t germinate. Several products available to homeowners are labeled for common chickweed including “pendimethalin”.

Redstem Filaree

  • Listed as a noxious weed in many states.
  • Deeply lobed leaves that somewhat resemble a fern.
  • Small, brightly colored five petaled flowers.
  • Strong, but not unpleasant smell.
  • Seed pods resemble a bird’s beak.

“Redstem Filaree photos by Steve Matson, 2004”

Weed Identification

Redstem filaree, also called California filaree and redstem stork’s bill, is considered an invasive and noxious weed in many states. It is a low growing cool season lawn weed that has both a taproot and fibrous root system. After germination, it begins growing in a rosette pattern and can either continue growing prostrate or in an upward fashion.

Redstem filaree has hairy and reddish colored stems. The leaves are deeply lobed and attach alternately on the stem with no petioles. Some other species of filaree have leaves that are not quite so lobed. Because of the shape of the leaves, it is often confused with a similar looking weed called Carolina Geranium.

The flowers of redstem are pink to purple, approximately ½ wide with 5 petals. It flowers profusely in the spring and to a lesser degree through fall. The seed pods resemble a bird’s beak and tend to grow together in clusters. As the pods mature, the tops often curl like a pig’s tail.

Cultural Practices

Redstem Filaree is a common weed on roadsides, fields, and poor quality lawns. It can be found in much of the U.S., including semi-desert climates. The best way to keep this weed out of lawns is to work on building a thick, healthy turf. Most lawn weeds cannot compete with thick turfgrass. The plant can be pulled by hand since it doesn’t root at the nodes.

Herbicide Use

Many homeowner herbicides do not do a great job at controlling this weed. The effects are marginal. Using common herbicides as 2,4-D plus Dicamba can offer some control, but not exceptional. Look for formulation with at least three different herbicides mixed together for better effect. Adding a “sticker/spreader” to the herbicide mixture increases it effectiveness in controlling lawn weeds. It works by binding the herbicide to the plant which aids in the absorption. (See the page on Herbicides for more information.)

Small and Large Hop Clover

  • A common forage crop, but also grows extensively throughout the U.S.
  • Low growing cool season annual with yellow globe flowers.
  • Stems are green to reddish colored.
  • Leaves consist of three leaflets.

Weed Identification

Large and small hop clover are very similar except that large hop clover, like the names sounds, is just a little larger. All annual clovers, including it relative black medic, are low growing. In unmowed areas, such as hillsides or pastures, it can grow more upright, extending a foot or more in height.

The leaves alternate and consist of three leaflets. The center leaf is on its own petiole. The stems feel a bit woody and are green to reddish (small hop clover) in color.

The flowers are globular and grow in clusters. In mowed turf, the plant tends to grow prostrate with stems laying flat on the ground. Large and small hop clover spread by seed.

Cultural Practices

Since this species of clover prefers fields and other low maintenance areas, working on a thick turf will keep most of it out. If your lawn is in poor condition, it may take a couple of years to get it where you see a major reduction in lawn weeds. Pulling or hoeing may reduce the amount of lawn weeds present, but seeds are in the soil guaranteeing another crop in the fall.

Herbicide Use

Herbicides may be the quickest means of controlling this weed. Since it is an annual, a preemergence may be useful to prevent the seeds from germinating. It will need to go down before the seeds germinate. After germination, preemergents will have no effect.

For growing weeds, a post-emergent broadleaf herbicide will need to be used. Look for herbicides with a three or four herbicide mixture for best control. Dicamba with MCPP or MCPA should help give some control. Check the label to make sure it lists your target weed.

Virginia Pepperweed

  • Winter annual found throughout most of the U.S.
  • It prefers dry soil conditions in full sun locations.
  • The stems grow erect and are multi-branched.
  • Leaves grow alternately on the stem.
  • Almost all seeds germinate in late summer or fall.

Weed Identification

Virginia Pepperweed is a small mustard-like winter annual that develops from a taproot. As with most annual lawn weeds, it is found in poor quality lawns, roadsides, gardens, and low maintenance areas. It forms a rosette pattern when young, but later develops upright stems. As it matures, it looses its basal leaves.

The leaves are toothed over most of the leaf. However, near the base of the leaf it becomes lobed. The leaves on the stem are arranged alternately.

One of the identifying marks is its seed pods. The seed pods look like tiny lily pads. They are round, but flattened disks that attach near the top of the stem. At the top of the stems are clusters of tiny white flowers with four petals.

Cultural Practices

Since the plant grows from a taproot it is possible to pull them up by hand. Since it is associated with poor quality turf, working on a thick turf will keep this weed and most other weeds out.

Herbicide Use

If you had problems with Virginia pepperweed before, there will be seeds in the soil from previous crops. Using a preemergent herbicide in late summer will work to stop weed seeds from germinating. Isoxaben is labeled for Virginia pepperweed. However, keeping lawn weeds out of bare soil is a difficult task even with a preemergent.

For established weeds you will need a post-emergent herbicide. Several herbicides are labeled for controlling this weed including 2,4-D, Dicamba, MCPP, MCPA, triclopyr plus clopyralid and others. Many herbicides will be formulated with 3 or 4 different herbicides for best control of weeds. Make sure the herbicide you use lists the target weeds on the label.

Use herbicides according to label instructions. Always be safe. Make sure you wear all personal protective equipment (PPE) listed on the label.

Crabgrass and Foxtails- Annual Grassy Weeds
Crabgrass and Foxtails are two major annual grassy weeds that can cover your lawn. You will find detailed information on their growth habits and how to control them before they even start.
Broadleaf Summer Annual Lawn Weeds
Many of the most problematic lawn weeds are annuals. Here you will find specific summer annual weed information, with weed names, photos and control methods.
Perennial Broadleaf Weed Identification Page 1
Click here for weed identification and control of common perennial lawn weeds. This page has detailed information on Canada Thistle, Mouseear Chickweed, White clover, Dandelion, Field Bindweed, Ground Ivy and Common Mallow.
Perennial Broadleaf Weed Identification Page 2
Click here for perennial weed identification and control. You can find detailed information on Buckhorn Plantain, Broadleaf Plantain, Red Sorrel, Wild Violets, and Common Yarrow.
Yellow and Purple Nutsedge
Nutsedge is a summer perennial grass-like weed. They can be particular problematic since they cannot be controlled by broadleaf weed herbicides. Click here for weed identification, growth habits and control methods.
Go from Winter Annual Brosdleaf Weeds back to Lawn Care Academy Home

Grounds Maintainance

If you’re fortunate, the only scares you’ll have this month are from the ghosts and goblins of Halloween and not the ineffectiveness of your weed-management program. With upcoming holidays and other fall-maintenance activities, you easily can forget about weed control. However, with appropriate action now, your weed problems will not come back to haunt you.

The weed-control strategy you should use depends on the types of weeds present. Therefore, the first thing you need to do is determine the major weed species at each property you maintain. You may need to use different strategies at the different sites, based on the predominant weed species. For example, wild onion may be the only serious weed at one site, while another location has common chickweed and annual bluegrass as the predominate problems. These two sites would certainly require different treatments.

In some ways, it’s easier to control winter weeds than summer weeds. However, if you neglect them, winter weeds can become a major burden in spring when you need to devote your time to other maintenance practices. Thus, treating for weeds now buys you time in the spring. And no matter what season it is, it is always easier to maintain a site in weed-free condition than it is to bring a heavily weeded site back into top condition. It pays to be proactive in your weed-control program.

Because we already have passed the peak period for winter-annual germination (which mostly occurs in September and October), your weed-management activities right now will have to address both the control of existing weeds and residual control for weeds that will germinate later. I hope that you applied pre-emergents in August because winter annuals germinate in early fall, with little germination during the coldest winter months. However, a second flush of germination can occur in early spring as temperatures start to rise. This is why some operators use split applications of pre-emergence herbicides: to control both flushes of germination. An August application for controlling fall-germinating weeds may no longer be effective by March, when more germination can occur.

Classification of winter weeds Most winter weeds fall into two categories: grasses and broadleaves. Weeds such as yellow nutsedge-neither a grass nor a broadleaf-are not a concern in winter because these plants go dormant with the onset of cold weather in the fall and do not emerge in spring until after temperatures have warmed up. Likewise, you cannot control warm-season grasses such as dallisgrass and bermudagrass in winter because these species also go dormant.

Broadleaf weeds consist of annuals, biennials and perennials. Examples of winter annuals include common chickweed, corn speedwell, vetches, rockets and henbit. Biennial weeds include certain thistles, such as musk thistle. Perennial winter broadleaves include bulbous buttercup and mouseear chickweed. In addition, seed of certain perennials that grow actively in warmer weather, such as dandelion and buckhorn plantain, often germinate in fall and early spring and therefore need attention in a fall weed-management program.

Grasses are either annual or perennial. Annual bluegrass is a common winter-annual weed. A perennial biotype of annual bluegrass exists, but this predominately is a golf-course problem. Quackgrass is a cool-season perennial grass that can invade turf and ornamental beds. If you maintain warm-season turf, you know that clumps of cool-season grasses such as tall fescue become quite apparent when the turf goes dormant. Cool-season grasses can be a conspicuous weed problem in such circumstances.

Other perennial monocot weeds (that are neither grasses nor broadleaves) of concern in fall and early spring include wild onion, wild garlic, grape hyacinth and star of Bethlehem. As in summer, perennial winter weeds are harder to control than annuals.

Weather conditions Weather conditions obviously are quite different in winter than summer, and this can impact weed management, especially herbicide applications. Temperature is an important factor for post-emergence herbicide application. Applicators frequently ask me about the minimum temperature in which they can apply post-emergents. This is not an easy question to address. I prefer air temperatures above 60 degreesF, with good soil moisture so weeds are actively growing. As temperatures drop, two effects occur. First, the development of injury symptoms is much slower compared to applications at higher temperatures. This does not necessarily mean that control ultimately will be worse. But if, for example, a herbicide takes 1 week in summer for effects to become visible, it may take 2 or 3 weeks in the winter. Thus, you may need to inform your clients not to expect fast results in the winter. Some weeds, such as henbit, seem to take an especially long time before complete control is apparent.

In some cases, however, control is less in winter because herbicides are not readily absorbed and translocated at low temperatures. This is a greater issue with systemic compounds than with contact products. Generally, I feel that ideal conditions for systemics are above 60 degreesF, while 50 degrees to 60 degreesF is acceptable, and 40 degrees to 50 degreesF is marginal. Avoid applications below 40 degreesF. Some applicators have told me that their cutoff temperature is 50 degreesF, but I have successfully used post-emergence herbicides at temperatures between 40 degrees and 50 degreesF. Nevertheless, applications below 50 degreesF increase the chance of erratic control, and you may have to retreat some sites. As in summer, it’s best if no rain or irrigation occurs for at least 24 hours after applying a post-emergent.

Cold weather generally is not a concern for pre-emergence herbicides and can actually help certain products. Volatility losses are less in cold temperatures, a benefit for products such as trifluralin and dichlobenil which can volatilize during warm temperatures. Also, herbicide breakdown by microorganisms is slower in low temperatures, increasing herbicide longevity and, thus, the length of weed control for pre-emergence herbicides.

Rain and falling snow help incorporate applied pre-emergence herbicides. Further, due to cooler temperatures, the need for immediate rainfall or irrigation for incorporation can be less critical than it is in summer. However, do not apply pre-emergence herbicides to frozen ground or ground covered by snow.

Winter weed control in turf You may need different programs for warm-season and cool-season turf. You can take advantage of the dormancy of bermudagrass to use products that would injure the turf during active growth. This allows you to selectively suppress species such as tall fescue growing in dormant bermudagrass. Conversely, cool-season grasses are actively growing in cool conditions and are susceptible to these products. However, on overseeded warm-season turf, your control strategies must accommodate the presence of the actively growing overseeded species. * Cool-season turf. In cool-season turf, you can control emerged broadleaf weeds using combination products that contain two or more of the following active ingredients: 2,4-D, 2,4-DP, MCPA, MCPP, triclopyr, clopyralid and dicamba. Because deciduous trees and shrubs drop their leaves in the fall, the potential hazards from volatilization and drift are less at this time than in the summer. This especially applies to ester formulations, with which volatility on hot summer days can be significant. However, ester formulations penetrate the waxy coating of leaves better than amine formulations, so fall offers a good window of opportunity for weed control with ester formulations of broadleaf herbicides. Products containing 2,4-D also can control wild onion and wild garlic.

On newly seeded turf, the stand must be well established before you can treat it with a post-emergence broadleaf product. You usually can treat if the site has been mowed three times.

You can apply isoxaben in fall for pre-emergence control of broadleaves after you’ve treated existing weeds with a post-emergence product. Isoxaben not only controls broadleaf weeds as they germinate, it also reduces regrowth of certain perennial broadleaf weeds that your post-emergence product may not have completely controlled.

Some pre-emergence grass herbicides also control certain annual broadleaves from seed. However, the primary benefit of “crabgrass preventers” at this time of year is to stop germination of annual bluegrass, along with providing early season summer-annual grass control. Examples of these products include dithiopyr, prodiamine, pendimethalin, benefin plus trifluralin, bensulide and oxadiazon. Just remember that if you treat turf with a pre-emergence crabgrass herbicide in the fall, this might affect reseeding the following spring. Products vary in this regard, so check the label for specific information.

You can use ethofumesate for post-emergence control of annual bluegrass in a range of cool-season grasses. You may need multiple applications for acceptable control. In bermudagrass, you only can use ethofumesate when the turf is dormant. * Warm-season turf. In warm-season turf, greater options are available for winter-weed control. In addition to conventional pre-emergents, you can use products such as atrazine, simazine, metribuzin, pronamide and imazaquin. These herbicides provide both pre-emergence and post-emergence annual-weed control, including annual bluegrass and broadleaf weeds such as common chickweed. Check the labels for tolerant warm-season species and the weeds that these products control.

Glyphosate and diquat provide post-emergence annual-weed control in dormant bermudagrass. Glyphosate, pronamide and atrazine also control cool-season perennial grasses such as tall fescue, bluegrass and orchardgrass. Imazaquin and 2,4-D products control wild onion and wild garlic. Post-emergence broadleaf combination herbicides control existing broadleaf weeds, and you can add isoxaben to the application for residual broadleaf weed control.

Winter weed control in ornamental beds Winter weed control is more difficult in ornamental beds than in turf, especially broadleaf weed control. Essentially no chemical exists for selective control of emerged broadleaf weeds in ornamental plantings. You must treat existing broadleaf weeds with careful applications of non-selective products such as glyphosate, diquat or glufosinate.

A much better strategy is to use pre-emergence herbicides for control of annual weeds in landscape beds. In woody ornamentals, use a combination treatment, such as a sprayed application of isoxaben with a grass herbicide such as pendimethalin, oryzalin, oxadiazon, napropamide or prodiamine, or apply a granular pre-pack combination such as Snapshot, OH-II or Rout. Dichlobenil is another option for controlling a wide range of weeds, including certain perennials, in woody ornamentals. These combination treatments control a wide range of annual weeds if you apply them before germination (dichlobenil also has post-emergence activity). In bedding plants, the best option is to use one of the granular crabgrass products. Check the labels for these products to determine the tolerant ornamental species.

People frequently ask me how to control chickweed and vetch in beds. The preferred strategy is a fall application of a pre-emergence herbicide before these weeds germinate. In spring, your best option generally is hand-weeding.

Weed identification and knowledge of herbicide selectivity is important for ornamental as well as turf areas. Most of the post-emergence grass herbicides available for use on broadleaf ornamentals will not control annual bluegrass. Although clethodim will provide some control of Poa annua, the best option is to use a pre-emergence crabgrass preventer for annual-bluegrass control. Control cool-season grasses-such as quackgrass, tall fescue and orchardgrass-with post-emergence grass herbicides such as sethoxydim, fluazifop or clethodim. If you intend to add mulch, do so after application of a pre-emergence herbicide. Also, you can use landscape fabrics to improve weed control over mulch alone.

Assess the sites you maintain for the presence of weeds. Develop a program to control both the existing weeds, as well as weeds that will germinate later. Beneficial results from such a program will be apparent in spring, when instead of playing catch-up, you’ll have time to devote to more pressing maintenance tasks.

Dr. Jeffrey Derr is an associate professor of weed science with Virginia Polytechnic Institute and State University (Virginia Beach, Va.).

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