Vegetable garden cover crops

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PHOTO: Rachael Brugger by Samantha Johnson July 8, 2013

Your vegetable garden is a busy, productive place—for part of the year, anyway. Outside of the growing season, garden soil sits dormant, waiting for your vegetable crops to take their place the following spring. But you don’t have to let that garden soil sit empty and unproductive; instead, plant cover crops that can offer myriad benefits for minimal labor.

You might associate the concept of cover crops with large-scale, commercial farming enterprises. After cash crops are harvested, farmers often plant cover crops to keep the soil covered, reduce weeds, prevent soil erosion and add organic material to rejuvenate the soil with nutrients. You can obtain similar benefits on a smaller scale when you incorporate cover crops (aka “green manure”) into your home or kitchen garden. Here are five cover crops that just might suit your small-scale needs.

1. Annual Rye Grass

Grasses are quick to germinate and generally more effective at controlling weeds than legume cover crops, which are some of the reasons that annual rye grass is such a popular cover crop. Depending on your preferences and your garden’s specific needs, you can seed annual rye grass among your vegetables or wait until you’ve harvested your veggies and plant rye grass as a winter cover crop. In the spring, trap the nutrients by cutting and turning under the rye grass to incorporate it into the soil.

Unfortunately, grasses don’t increase the nitrogen in the soil, which is why you’ll also want to consider pairing it with a cover crop from the legume family.

2. Hairy Vetch

A popular legume cover crop, hairy vetch is commonly used in vegetable gardens and is valued for its nitrogen-fixing ability. Additionally, hairy vetch is impressively versatile and resilient; it’s a good choice in cold climates and drought conditions, and it performs well in a range of soil types and pH levels. Plant hairy vetch in late summer or early fall, and till it under in spring. Alternately, you can mow it down and plant your vegetables directly in the resultant mulch a few weeks later.

3. Buckwheat

If controlling weeds in your vegetable garden is your goal, then consider to checking out this effective “smother crop.” Buckwheat is a non-legume cover crop that’s sensitive to cold, making it perfectly suitable for summer planting. Plant buckwheat any time between late May and late August, and incorporate it into the soil about 40 days after planting. It’s a convenient choice for simultaneously invigorating your soil and minimizing weeds.

4. Red Clover

If you like the concept of one-stop shopping, then red clover as a cover crop will undoubtedly delight you. This legume provides ample quantities of nitrogen and valuable quantities of biomass that benefit your garden soil. Seed red clover among your rows of growing vegetables anytime from spring to early autumn.

5. Winter Rye

As its name implies, winter rye is a winter cover crop suitable for overwintering in many locations thanks to its incredibly hardy and resilient nature. Sow winter rye in late summer or early autumn after your vegetables have been harvested, and then watch out! It grows quickly and vigorously, and will resume growth in spring, at which time you can plow it under and put the winter rye biomass to work in your soil.

Get more soil-boosting garden tips:

  • 6 Soil Problems and Amendments to Fix Them
  • Build a Soil Sifter
  • Soil Testing Chart
  • 10 Natural Fertilizers to Improve Crop Production
  • Bring Clover on Over

Cover crops and green manures in home gardens

Planting cover crops

Some gardeners sow cover crops plants in spring, especially in new garden plots to improve the soil and choke out weeds. In established vegetable or flower gardens, plant a green manure early in the season to improve the soil. After you turn it under, plant warm-season vegetables, bedding plants or container-grown perennials.

If you dig a new garden bed in spring or early summer, grow one or two crops of heat-loving buckwheat or beans. If you start a new garden in late summer, plant ryegrass, rapeseed or oats, which grow quickly in cool weather.

In late fall or the following spring, turn in the dead plant material and plant flowers or vegetables in the new, improved bed. The soil will contain more organic matter and beneficial microorganisms. There will be fewer weeds than before.

Use green manures in established vegetable gardens after you harvest early-maturing vegetables. You can plant green manure where these vegetables were growing to keep the garden weed-free, prevent soil erosion and add organic matter to the soil. Turn in the dead plant material after a killing frost in late fall.

Sow the seed thickly to create a cover that will not allow weeds to compete. Mow the plants down if they flower, to prevent them from self-seeding and becoming weeds themselves. In spring, turn dead plant material from green manures into the soil before sowing seeds or transplanting seedlings. This is also the time to add fertilizer to the soil. If the green manure does not die over winter, wait about two weeks after you turn in the living plant material before seeding or transplanting.

Cover Crops

SERIES 19 | Episode 09

During the wet season it’s often so hot and humid that the last thing I feel like doing is slaving in the vegie garden. But the danger of leaving the garden unattended is that weeds run riot, and torrential rainfall strips nutrients from the soil. The way to counteract this is to plant cover crops.

These are plants that use nutrients in the soil and store it in their plant bodies before the rain washes it away. The nutrients are then returned to the soil when the cover crop is dug in at the end of the wet season. And because they’re nice, thick and lush, they really work to keep weeds at bay.

Ideal cover crops are green, leafy and use lots of nutrients. Legumes are great because they grow quickly and hold lots of nitrogen. Another advantage is that the bacteria associated with their roots can absorb nitrogen from the air and soil. Lablab is a fast growing legume so you can chop it throughout the wet season and still have enough nitrogen rich leaves to dig back into the soil. Cover crops can also be useful to control nematodes. These are tiny threadlike wormy creatures that live in the soil. Most are beneficial. But the plant feeding variety can invade roots and starve and kill plants. Planting crops that nematodes don’t like, such as corn, sorghum, peanuts, marigolds or spear grass breaks the cycle.

While cover crops are protecting the soil, try growing cassava. The new green leaves are a beautiful vegetable to eat, but it’s what’s under the ground that’s really delicious. The tuberous root can be sliced and fried like chips; boiled and added to vegetable dishes; or made into flour and used in bread and cakes. Cassava grows easily from cuttings. Take lengths that are about 30cm long and 1.5cm thick from the woody part of the plant. Remove leaves and plant into a shallow trench in the ground. Cassava grows into tall spindly bushes that are easily blown over, so prune heavily to keep them to about a metre high.

Once wet season cover crops are planted, it’s a perfect time to start building large piles of compost. Everything decomposes amazingly quickly at this time of year. I wait until the cooler time of day and collect the dry and green leaves and lawn clippings – anything that’s high in nitrogen. This is thrown in a pile on the vegie garden. The basic proportions are one wheelbarrow of green to two to three wheelbarrows of hay or dry leaves. Add branches and palm fronds to keep the pile aerated and you won’t even have to turn it. A good tip is to throw a tarp over it and this stops the heap getting wet and soggy.

Before you know it, the wet season will be over. There will be loads of beautiful compost and the cover crops will be ready to be dug back into the vegie garden – to return all the goodness they’ve been storing, back into the soil.

Basics of Cover Cropping

Considerations for Deciding What to Grow

What is the crop time?
Figure out how long it will take your cover crop to mature from the time you seed it to the time you kill it. The trick to getting the maximum benefit of cover crops is to allow the crop to get as mature as possible without making seeds. When the time comes that you can let it go no further, you kill it, allowing it to provide a layer of mulch on the soil, which feeds the soil food web below as it decomposes.

How will you kill the cover crop?
There are a variety of methods for killing a cover, but the most popular for home gardeners is mowing, weed eating, or just chopping down with some loppers. However, make sure you’re working with a cover crop that will die from mowing, otherwise you’ll end up with a regenerating cover, which may not be what you’re after. For example, winter annual rye will only die-by-mowing after it creates a seed head, but before it releases its seeds. Austrian winter peas, on the other hand, can be mowed anytime and will die.

How long will it take the cover crop residue to decompose?
Residue that is tender, like buckwheat or peas, will be assimilated by the soil critters much faster than sorghum stalks or barley stems. This is important based on what you plan to do with that bed after cover cropping. Do you want to kill the cover crop and plant seeds as soon as possible? If so, consider a tender cover like buckwheat. Do you instead want to kill the cover crop and have its residue provide mulch on the soil for as long as possible? If that’s the case, sturdier, carbon-rich crops like oats or sorghum are great options.

What is the season?
Some cover crops are best for summer, like cowpeas, soybeans, and sorghum-sudangrass hybrids, whereas there are other specific cover crop options for wintertime, such as winter wheat, clovers, and Austrian peas.

What is the subsequent food crop?
Knowing what you want to grow after the cover crop is done will help you select the best cover crop species. For example, if you plan to grow a high-feeder (a crop that pulls a lot of nutrients from the soil), like tomatoes, it’s a great idea to precede the tomato crop with a leguminous cover crop like field peas or clover, which will add nitrogen to your soil. On the other hand, some cover crops can have negative effects on the food crop you plan to plant. Winter rye residue is allelopathic (releasing toxic chemicals as it decomposes) to seeds of certain brassica species. If you are prepping soil for your spring cole crops and are planting from seed, consider a different cereal grain like wheat, instead.

Winter Cover Cropping : A Fine Time to Build Soil

The best winter cover crops differ from region to region, by growing zone and the crop’s winter hardiness, but from a management perspective there are basically two types, winter-killed and winter-hardy, along with a third, blended type of the two.

1 • Winter-killed cover crops: Killed by cold, but have sufficient biomass to protect the soil.

Depending upon growing zone, the peas, clover, and ryegrass in the mix are winter-killed, while the rye and hairy vetch regrow in spring.

Oats are an prime example of this first type. Sown in summer, they will put on a lot of growth, and often maintain active growth into early November, dying slowly after several hard frosts. The winter-killed mulch and root mass will hold the soil in place, however, until the following spring.

Other crops that may be grown for winter-killed mulch include field pea, oilseed radish, and rapeseed.

The caveat with this type of cover crop is that you have to clear the land and plant the cover crop early enough to get significant amounts of biomass to hold the soil over the winter. That could mean winter cover-cropping only on ground that grew spring vegetables, or it could require undersowing the cover crop in a summer crop such as corn. The big advantages of a winter-killed cover crop is that the mulch is easy to till under in spring, and the land can be planted right away.

2 • Winter-hardy cover crops: Survive through winter, resume growth in spring.

  • Establishes ground cover quickly.
  • Hardiest winter cover crop to stem wind & water erosion.
  • Deep & extensive root structure prevents compaction, improves soil tilth.

The second, winter-hardy type can either grow through winter or go dormant for a period when temperatures and/or daylight reach a certain threshold, then renew growth in late winter.

They can usually be planted after the summer vegetable crops, and will grow through fall to establish root systems that protect the soil from the dynamic forces of wind and water over winter.

Some examples of crops that will survive the winter — depending on winter temperature lows — include winter rye, winter wheat, hairy vetch, Austrian winter peas, and crimson clover. Winter rye and hairy vetch are recommended for the northern United States.

In regions where these crops survive winter, they will grow vigorously in early spring. They will need to be mowed close to the ground, to stop growth, and then incorporated into the soil. Because decomposition of the cover crop debris will tie up nitrogen, it’s a good idea to wait two or three weeks before planting.

Mixed winter-hardy & winter-killed cover crops

Many growers use a mixture of cover crops from the two categories. Johnny’s Fall Green Manure Mix is a blend of winter rye, field peas, ryegrass, crimson clover, and hairy vetch. The peas, clover, and ryegrass are winter-killed. The rye and hairy vetch regrow in spring.

Winter forage

Take note that if deer are numerous in your area, they tend to prefer winter rye over almost all other winter cover crops. You may want to consider sowing a mixture of medium red clover and oats, as the deer do not like oats as much.

Another practice would be to sow forage turnip around the perimeter of the field to satisfy the deer’s hunger. Sown by mid-August, turnips will generally grow slowly until temperatures fall below 20°F/-6.6°C. While turnip bulbs remain grazeable even after freezing, they do begin to deteriorate soon after a thaw.

Using Cover Crops in the Home Garden

Circular 1057 View PDF picture_as_pdf

Robert Westerfield, University of Georgia Department of Horticulture, Extension horticulturist
Carmen Westerfield, U.S. Department of Agriculture, district conservationist

Cover crops can be an important component to any home garden. They are used for various reasons, including building the soil, controlling soil erosion, and limiting the initiation and spread of certain diseases and insects in the soil. Cover crops are primarily used to “rest” or leave a garden area open during non-production times. Therefore, they are most often planted in the fall. However, summer cover crops can be equally effective and can provide the same benefits as a fall cover crop.

Benefits of Cover Crops

It is important to mention the benefits of cover crops and why you should consider using them in your garden. Leaving an unplanted area of your garden as bare soil can easily lead to the germination of unwanted weeds and to damaging soil erosion. Cover crops are intended to cover this bare soil and provide a cheap source of nutrition for your garden plants, when cover crops are turned under and decomposed into the soil. They also increase the organic matter of the soil, as they break down into humus.

Cover crops look more attractive than bare soil and, depending on the type of cover crops you plant, can attract beneficial and pollinating insects. They can also be used between rows in your garden to help hold the soil and block weeds from germinating. Rotating between different vegetable families, as well as planting cover crops, can assist in starving out damaging soil pathogens by providing a non-host plant. Overall, the planting of cover crops is an essential organic method of protecting your garden, building better soil and increasing production.

Selection of Seed

The time of year will determine whether you plant a cool- or warm-season cover crop. Cool-season cover crops should be established after the summer garden fades, usually from early September into the first part of October. If you are not planning on planting a winter vegetable garden, you should consider seeding your entire garden in a cover crop.

Try using a combination of a cereal grain with some type of legume. Typically, wheat, oat or rye is planted with a legume, such as clover or winter peas. The grass-type cereal grain is quick to establish and helps hold and protect the soil while the slower germinating legume crop takes hold. Legume crops have the added bonus of fixing atmospheric nitrogen, which can be used by the crops that follow when the legumes are tilled into the soil. This can help reduce your fertilizer expenses.

A typical mix might be 3 to 4 pounds of a cereal grain with 0.25 pounds of a legume per 1,000 square feet. For a garden as large as an acre, you can go with 50 pounds of cereal grain and 5 pounds of clover per acre.

An important consideration is the use of a legume inoculant. Specific Rhizobia bacteria invade the roots of legumes, forming nodules where nitrogen fixation takes place. These bacteria are specific for different legumes and can be purchased to inoculate legume seed prior to planting. Inoculant comes in the form of a powder and is actually live bacterial. There are specific inoculants for various types of clovers and other legumes, so be sure to purchase the correct one.

Nitrogen fertilizer should not be applied to legume cover crops as this interferes with nitrogen fixation; however, applications of phosphorus and potassium according to soil test recommendations can enhance nitrogen fixation. Be sure you do not use ryegrass for a winter cover crop. Ryegrass is different than the cereal grain rye, and it is much too competitive and difficult to eradicate.

Summer cover crops can also be beneficial when you need to rest an area of the garden yet protect the soil from erosion and invasive weeds. Typical summer cover crops include buckwheat, millet, cowpeas, sorghum-sudangrass or soybeans. Depending on your selections, they should be planted at a rate of 1 to 5 pounds of seed per 1,000 square feet. They can be planted as a single cover crop or mixed in any combination; reduce the planting rate appropriately when mixing seeds.

Planting and Establishment

Cover crops establish quickly when planted on a well-prepared seedbed. Prepare the bed by removing old vegetable plants and tilling the area to a depth of 4 or 5 inches. Seed can be broadcast over the intended planting area at the proper rate discussed earlier. It is best to test the soil prior to planting to determine the pH and fertility needs of your cover crop. Lime and fertilizer can be applied at time of planting and should be tilled into the soil just prior to spreading seed.

After the seed has been planted, lightly rake or drag the seed into the soil to establish good soil contact. Tiny seeds, such as clover, should not be buried deeply; make sure they are just barely below the soil surface. If you happen to have access to a roller or cultipacker, it is an excellent idea to go over the seedbed with such a tool to help firm the bed and increase germination.

Water the newly planted area every other day for the first week or two to assist in germination. Once the cover crop is up and growing, you can cut back watering to once a week. A fully established cover crop will typically survive on rainfall alone.

Use in Prevention of Soil Erosion

One of the greatest benefits of cover crops is erosion control because cover crops reduce the amount of time soil is left bare. Living plants and plant residue intercept falling raindrops and absorb the erosive energy of the rain before the water reaches the soil. The cover also slows the flow of water across the surface and increases the rate at which the water soaks into the soil.

Cover crops address the management concepts of soil health by:

  • Disturbing the soil less (less is more).
  • Increasing the diversity of soil biology and assuring a successful growing area by using a combination of plants.
  • Keeping a living root system of plants growing throughout the year.
  • Controlling erosion and compaction before they start.

Status and Revision History
Published on Sep 30, 2014

Cover Crops For the Garden

Unlike garden crops planted for their delicious edible outcomes, cover crops planted between growing seasons boost soil health and ensuing vegetable production—a sort of crop’s crop. Planted in rotation with edibles, cover crops improve soil by adding and retaining minerals and organic matter. They also reduce soil erosion, and keep soil loosened and aerated, while increasing water infiltration and helping suppress weed growth. Some even attract beneficial insects.

Non-Legumes and Legumes

Cover crops divide roughly into two categories: non-legumes and legumes.

The best non-legume cover crops have fibrous root systems that reduce soil loss and take up nutrients that might otherwise leach out of the soil over the winter. Plus, their energetic growth suppresses weeds. Popular non-legumes for gardens are buckwheat; grasses such as oats, winter rye, barley and Sudangrass; and several plants in the brassica family.

The main advantage of legume cover crops is their ability to fix nitrogen gas in the atmosphere into nitrogen that can be used by plants. Most-used legume cover crops for the garden include crimson clover, hairy vetch and cowpeas.

While both types of cover crops contribute organic matter to the soil, non-legumes produce more of this biomass. Chopping or cutting back cover crops before they go to seed is the best practice to avoid unwanted reseeding. The cut organic matter is left on top of the soil as mulch or tilled under.

As mulch, cover crops continue to suppress weeds and add nutrients to the soil as they decompose. If you till non-legume biomass into the soil, do it several weeks before planting garden crops, because the actively decomposing materials “tie up” nutrients the newly planted crops need.

When and What to Plant

Summer cover crops are planted following harvest of short-season crops and cut prior to planting. Buckwheat provides excellent weed suppression, but it must be cut soon after it begins flowering to avoid unwanted reseeding. The legumes cowpeas and crimson clover are good for summer, and can be planted together with non-legumes for weed suppression and added nitrogen.

Winter-kill cover crops are planted after garden crops are harvested, then killed by freezing temperatures. The following spring, you can plant early-season greens and veggies right into the resulting mulch. Winter-kill cover crops include oats, brassicas and field peas for USDA Zone 7 and colder. Crimson clover will winter-kill in Zone 6 and colder.

Overwintered cover crops are planted late in the season. They are seeded even as late fall crops are being harvested and then live through the winter, providing weed suppression and ample biomass when chopped down before flowering the following spring. In temperate climates, good overwintering crops are winter rye, hairy vetch and crimson clover. In far northern regions, winter cereals such as rye, wheat and triticale are good choices.

Edible Ground Covers for Vegetable Gardens

When we think of ground covers, we often think of things like grasses, sedums, and other fast-spreading, low-growing plants that cover or creep along the earth. Essentially, they function as living mulches to reduce weeds and retain moisture by blocking sunlight.

But in a vegetable garden, where I’m trying to maximize production of my land in a way that’s beneficial to the ecosystem as well, I sometimes feel like a layer of mulch — even if it’s organic mulch like compost or straw — is a wasted opportunity to do something more.

There’s no denying the importance of mulch: In addition to smothering weeds and conserving water, it reduces soil erosion and helps curb the spread of disease in a garden (by preventing soil from splashing back up onto the leaves). It also keeps the garden neat and tidy, and most organic mulches eventually break down and add nutrients back into the soil.

But is there a better way to mulch in a vegetable garden so you can fully utilize every square inch of growing space?

Yes! Try edible ground covers.

Intercropping with Edible Ground Covers

In a way, planting edible ground covers in the patches and rows between your vegetables is a type of intercropping (also known as interplanting).

Intercropping is the practice of growing multiple crops within the same space in order to achieve a greater yield from land that otherwise would be left unused by a single crop. Usually, vegetable gardeners will tuck quick-growing crops like lettuces and radishes under taller and slower-growing crops like tomatoes and peppers.

While these early-maturing varieties make good understory plants, they need to be reseeded often so you’re not continually left with bare soil after every harvest.

A better option in a vegetable garden is to grow long-season annuals or non-aggressive perennials that stay low to the ground, don’t compete for nutrients, and have other benefits like attracting pollinators or repelling pests.

Here are my five favorite ground covers for vegetable gardens that are not only ornamental, but edible as well.

Easy-Care Edible Ground Covers

1. Nasturtiums

Most people think of nasturtiums (Tropaeolum majus) as flowers, but they’re also vegetables in their own right. (See my recipes for nasturtium pesto and poor man’s capers.)

These self-seeding annuals grow quickly on long, thin vines that drape over garden beds beautifully. Their lush green leaves are reminiscent of lily pads, and when they bloom, the flowers attract pollinators all day long, making them a good option as a ground cover for berries, cucumbers, and other crops that need more than just wind for pollination.

Nasturtiums are also highly attractive to aphids, which may sound like a nuisance to some, but this is what makes them such a great trap crop — that is, a crop that’s sacrificed in order to keep aphids off your more valuable crops. Plant them around susceptible crops and as soon as you see an infestation on your nasturtiums, pull the affected leaves so the aphids don’t jump to your other plants.

2. Oregano

Herbs like oregano (and its Mediterranean cousins, thyme and marjoram) are ideal for in-ground garden beds that see some foot traffic. They can tolerate a little trampling and still be effective as a ground cover. As a bonus: Stepping on oregano releases its fragrance into the air, and it’s these same aromatic oils that repel insects like mosquitoes and fleas.

Oregano (Origanum vulgare) is a loose, open plant that can grow up to 2 feet tall, but likes being pinched back to maintain a low and bushy growth habit. Creeping oregano (Origanum vulgare ‘Humile’), on the other hand, quickly spreads to form a dense mat under 3 inches tall. Bees love the clusters of delicate flowers that bloom in summer. (For humans, the flowers make a fragrant and pretty garnish for soups, salads, and other dishes.)

The herb is a cold-hardy, drought-tolerant perennial (often surviving freezing temperatures) and needs well-draining soil and full sun. That means it should only be used as a ground cover for plants with similar water needs, such as chard, okra, and artichokes. It also grows well with deep-rooted plants that don’t need to be continually saturated.

3. True French Sorrel

True French sorrel (Rumex scutatus) is what I sometimes call the uncommon sorrel, in contrast to the common sorrel or garden sorrel (Rumex acetosa) that’s more readily available in garden centers. (I wrote more about True French sorrel here, if you want an in-depth profile of this ancient herb.)

The plant is a low-growing hardy perennial with distinctive shield-shaped leaves. A couple of small plants will quickly grow into a patch less than 12 inches tall. In my own garden, where I planted True French sorrel in a bed that received partial shade, it stayed under 6 inches tall.

I love to grow it because it’s low-maintenance, not so common, and has a lemony flavor that’s unlike anything else in my garden. As a ground cover, it stays a brilliant green year-round and the clumps can be lifted, divided, and replanted elsewhere when you need to fill in some space in your beds.

4. Alpine Strawberries

Unlike garden strawberries (Fragaria ananassa), most varieties of alpine strawberries (Fragaria vesca) don’t self-propagate via runners, making them a friendly option for intercropping.

Since alpine strawberries produce tiny (yet delectably sweet and fragrant) fruit, many gardeners skip them in favor of big, juicy garden strawberries because they find the smaller, near-wild cultivars aren’t worth the effort. And it’s true that you would need several plants to harvest a single cup of alpine strawberries. (I promise that it is worth the effort once you’ve tasted them! Read more about the Yellow Wonder variety I grew in my garden.)

As an edible ground cover, however, alpine strawberries tick off all the boxes: tough yet non-invasive, and able to tolerate a variety of soil conditions (especially if you forget to water for a short spell). They have a low growth habit and tend to hold fruits up high, often above the leaves. And because of its pale color, Yellow Wonder, in particular, doesn’t attract birds the way bright red strawberries do.

5. Squash and Melons

If you’ve ever grown a Three Sisters garden (learn more about this Native American planting method, with suggested layouts for your own Three Sisters), then it should come as no surprise that squash and melons (Cucurbitaceae family) make excellent ground covers for large open spaces.

And that’s the key: They should only be planted in large open spaces, otherwise they could make it difficult for you to harvest your other crops (not to mention the amount of real estate they take up). The sprawling vines are thick and prolific (which is what makes them so effective as a ground cover) and have a tendency to climb, so they should be kept away from structures where their habit isn’t desired.

In small spaces, consider planting another cucurbit as an edible ground cover: cucumbers. Though we usually think of them as climbers, cucumbers grow perfectly fine along the ground. They still produce vigorous vines, but the smaller leaves and smaller fruits make them more manageable than squash and melons. Compact varieties like Mexican Sour Gherkins are another good option to try.

Choosing and planting cover crops for raised beds

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Once I pulled my garlic from its raised bed this summer, I hadn’t made plans to plant anything else in it. A few weeks later, I found myself with a giant raised bed full of weeds. Rather than pull them and allow more to make a home, I thought I’d plant a cover crop instead. So I headed to my local seed supplier, William Dam, which has a retail shop, to ask about the best cover crops for raised beds.

What are cover crops?

On a broader scale, cover crops are planted by farmers to revitalize and improve the soil structure in their fields between plantings. You might see the word tilth used in descriptions of cover crops. Soil tilth refers to the health of the soil. A variety of factors from aeration and soil composition to moisture content contribute to the health of your soil (or lack of).

Cover crop seeds are sown in your raised bed, and the plants are later turned into the soil. An added bonus? These fast-growing, shallow-rooted crops help to prevent weeds. Cover crops are also known as green manure or green crops, because you’re basically growing your own compost.

Planting cover crops for raised beds

How do you make this nutrient-rich compost? Fall is a great time to grow cover crops because your veggie-growing season is coming to an end, and the beds will be empty until spring. When you’re ready to plant your cover crop, pull all the existing plants and weeds out of the raised bed. Densely seed your raised bed in late summer or early fall. Be sure to read the seed packet for timing as some plant varieties need warmer weather to germinate than others. However you don’t want the plants to mature before the winter. Some cold-tolerant cover crop varieties can be planted up to a month before your first frost date.

I just sprinkled the seed mix that I chose from my hands, being sure to broadcast the seed evenly throughout the raised bed. I want the plants to grow close together to keep the weeds away!

Allow the cover crop plants to grow through the fall and forget about them until spring. Plants will grow until winter arrives. Some varieties will go dormant and others will be killed off by the winter weather. In the winter, plants help to provide cover for microorganisms to overwinter. In the early spring, if they’re perennial, the plants may provide nectar for early pollinators, depending on when you mow them.

You want to make sure you mow down your plants before the seed heads mature. In a raised bed, I will likely use my whippersnipper (edge trimmer) to cut the plants. You could also try using your lawnmower. Then, I’ll use a rake to lightly turn the plants into the soil. (I’ll add photos of this process in the spring of 2020.)

You want to give the plants a few weeks to decompose before sowing seeds or digging in transplants. I’ve seen recommendations range anywhere from two to four weeks, to four to six weeks. Consult the seed packet for this info.

Which cover crops should you plant in your raised beds?

There are a few options to consider when choosing cover crops for raised beds. Niki has planted buckwheat, fall rye, alfalfa, and white clover in hers.

My 50/50 pea and oat mix to add to my raised bed as a cover crop.

Peas and oats: At William Dam, it was recommended that I plant a pea and oat 50/50 mix. It’s listed as a “very effective nitrogen and biomass builder.” And that the oats will utilize available nitrogen, building soil structure and suppress weeds (which is what I need them to do), while the peas will fix nitrogen for the following crops (which I will plant next spring). I will allow the plants to die off over the winter and then till the plants into the soil in the spring.

This raised bed owner grew oats as a winter cover crop because they die over the winter in cold climates. Then in spring, she chopped them up in the bed with her mower and left the residues in place to serve as a mulch.

Buckwheat (pictured in main image): Not only is buckwheat fast growing, it also breaks down quickly. If you let it flower, it will attract pollinators and beneficial insects. Mow the plants within 10 days of blooming, or anytime before.

Winter rye: This is a fast-growing crop that doesn’t mind the cold. You can plant it later in the season than many other plants. It’s touted as a great soil builder that helps to loosen compacted soil.

Winter rye is touted as a great soil builder that helps to loosen compacted soil.

Clover: Clovers fall under the legume category with alfalfa, which is typically used in farmers’ fields. White Dutch clover is a popular cover crop choice because of the flowers, which will attract bees. Some gardeners are starting to use this in their lawns, as well. Clover also attracts beneficial ground beetles and helps to combat cabbage worms. Crimson clover has really pretty flowers and doesn’t mind a bit of shade. This might be a good choice for a couple of my raised beds that get more dappled shade from the expanding tree canopy than when I first placed them.

White Dutch clover is popular both as a cover crop and in lawns.

I will report back with images of my cover crop!

Check out these raised bed articles for more tips:

    • The best soil for a raised garden bed
    • DIY potting soil
    • A compost how-to guide
    • Planting a raised bed
    • The benefits of raised bed gardens

Use Cover Crops to Improve Soil

How to Take Cover Crops Down

Speaking of taking down, this is the sticking point for most gardeners when it comes to cover crops, which is why it’s a good idea to start small with your first cover crop plantings. Traditionally, cover crops are plowed under, but most gardeners chop, cut, or pull them, and use them for mulch or compost. Or you can assign the task to a flock of pecking poultry. All are sound methods, and it is possible that composting cover crop plants produces a more balanced soil amendment compared to chopping raw-crop residue directly into the soil. Pulling plants saves time, too, because you don’t have to wait three weeks (or more) to plant, in order to avoid possible negative reactions between rotting plant residues and the plants you want to grow. For example, the cover crop known as sudex (a fast-growing sorghum-Sudan grass hybrid) produces gargantuan amounts of biomass (leaf, stem, and roots), but fresh sudex residue in the soil inhibits the growth of tomatoes, lettuce, and broccoli. Oats, wheat, and other cover crop plants also produce allelopathic substances that can temporarily hinder the germination and growth of other plants, too, but not in quantities sufficient to cause serious disturbances in the garden. If you chop in fresh cover crop residues, just plan to wait two to three weeks before sowing crop seeds.

Top Cover Crop Options

The following cover crops work well in a wide range of climates and situations, and they’re not hard to take down, as long as you do it at the right time and in the proper way. We’ve selected these six because they are easy to manage using hand tools, grow during different seasons, and provide multiple benefits in the garden.

During the summer, buckwheat (Fagopyron esculentum) is in a class by itself as a cover crop. Seeds sown in moist soil turn into a weed-choking sea of green within a week, with many plants growing 2 feet high or more and blooming in less than 30 days. Should you need to reclaim space that has been overtaken by invasives, buckwheat can be your best friend. In my garden, buckwheat has been a huge ally in cleaning up a spot overrun by dock, bindweed, and other nasties that grow in warm weather. For two years, each time the noxious weeds grew back, I dug them out and planted more buckwheat. Throughout the battle, the buckwheat attracted bees and other buzzers in droves. Fortunately, even mature buckwheat plants are as easy to take down as impatiens — simply pull the succulent plants with a twist of the wrist, or use a hoe or scythe to slice them off at the soil line. You can let the dead plants die into a surface mulch and plant through them, gather them up and compost them, or chop them into the soil.

In late summer, while the soil is still warm, you have a fine opportunity to try barley (Hordeum vulgare), a fast-growing grain that’s great for capturing excess nitrogen left over from summer crops, which might otherwise leach away during the winter. Barley often suffers from winter injury in Zone 6, and is often killed altogether in Zone 5 and above. This is good! The dead barley residue shelters the soil through winter, and dries into a plant-through mulch in spring in cold zones.

Early fall is the best time to grow the dynamic duo of soil-building cover crops — oats (Avena sativa) mixed with cold-hardy winter peas (Pisum sativum). When taken down just before the peas start blooming in spring, an oat/pea combination cover crop is the best way to boost your soil’s organic matter and nutrient content using only plants. Both make a little fall growth when planted in September, and in spring the peas scramble up the oats. On the down side, one or both crops can be winterkilled before they have a chance to do much good north of Zone 5, and in more hospitable climates it will take some work to get the plants out of the way in spring. Do it by mid-April, because the job gets tougher as the plants get older. Cut or mow them down first, and then pull and dig your way through the planting. A heavy-duty chopping hoe works well for this.

Hairy vetch (Vicia villosa) needs a good head start on winter, too, but it’s hardy to Zone 4 and gives a huge payback in terms of soil improvement, and saved time and labor. Unlike many other cover crop plants, you can quickly kill hairy vetch by slicing just below the crown with a sharp hoe. When hairy vetch is beheaded about a month before it’s time to plant tomatoes and peppers, you can open up planting holes and plant through the dried mulch — no digging required.

Late fall is not a lost season for cover crops, but in most climates you’re limited to cereal rye (Secale cereale), the cold-hardiest of them all. Rye will sprout after the soil has turned chilly, but be sure to take it out early in spring, before the plants develop tough seed stalks. Or let your chickens keep it trimmed; leave the birds on the patch longer in spring and they will kill the rye for you. If you’re looking for a cover crop you can plant in October for cold-season poultry greens, cereal rye is probably the best choice.

In any season, you may find many more great cover crops in seed catalogs, or among your leftover seeds. As you consider possibilities, think about plants that quickly produce an abundance of leaves and stems, but are easy to pull up or chop down if you decide you don’t want them. Bush beans, leafy greens, or even sweet corn can be grown as short-term cover crops, along with annual flowers such as calendulas and borage in early spring, or marigolds and sunflowers in summer. Teaming up a flower with a cover crop plant is always fun, whether you’re planting sulphur cosmos with cowpeas in summer, oats with dwarf sunflowers in late summer, or bachelor’s buttons with crimson clover in the fall. Whatever you do, just don’t leave your soil bare or you’ll be missing out on a chance to capture solar energy to recharge your food web.

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To locate mail-order sources for cover crops, go to the MOTHER EARTH NEWS Seed and Plant Finder.

Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.

I am finally getting around to writing this, ah well. Let me begin by wishing you all a happy height of gardening season! The weeds and the fruit and the veggies and the flowers are keeping me hopping, as I imagine you are. Ah, but the pay-offs are worth it. Now, let me share another bit of garden discovery with great pay-offs: Cover crops. When I first started gardening, I knew nothing about cover crops. As time and experience went by, I learned of this practice, but was convinced (for whatever reason) that this was a large scale agriculture idea, not suitable for a small backyard plot. Then, a couple of years ago, I was somehow motivated to revisit the idea – call it an inspiration or a garden tweet, I don’t know. Anyway, my curiosity and research led me to numerous articles on the Internet that assured me this practice is of great value to home gardeners and has been used by many. Surprise, surprise, surprise!

So, let’s start at the beginning. A cover crop is planted for the purpose of improving soil quality and nutrition and, perhaps, for attracting beneficial insects. Cover crops improve the quality of soil by adding nitrogen and organic matter, and improving soil tilth and water penetration. One that is planted in the fall and tilled under in the spring is often referred to as “green manure”. This addition of organic matter feeds the soil dwelling fungi and bacteria so they can release nutrients back into the soil. Cover crops also choke out weeds and stabilize the surface of the soil while breaking up and aerating with their deep reaching roots.

I don’t remember seeing seed for cover crops in any nursery or seed catalog until recently. Now quiet a few of the better suppliers carry a wide variety. In choosing which cover crop you want to try, you must consider what you are hoping to accomplish. Cereal crops, such as winter rye, will help build organic matter. Addition of nitrogen would call for a legume crop, such as vetch or peas. If you want the best of both worlds, you can choose a seed mix. Just remember, if you choose a legume, you will need to employ an inoculant when you plant. You probably already do that with your sugar snap peas and bush beans, right?

Most home gardeners would want to put in a cover crop for winter. The idea is to reap the benefits without much work. If you plant a winter garden, this might be a drawback. But, if you are not much of a winter gardener, then putting in a cover crop is great for suppressing weeds, and requires minimal watering. Planting is easy. Just prepare the bed, scatter the seed and rake it in, then cover with a mulch of straw. A new planting will need water for germination and to get a good start, then just minimal watering and no additional fertilizer. In the spring, let the crop grow until about a month before you want to plant. Then, weed whack the cover crop and turn it in with a rototiller or spade.

The first year I tried this, I planted winter rye – mostly because I got a late start on the project and didn’t get the seed in until late October. This is a hardy grain and did just fine. I did not let the seed heads mature and decided to pull the stalks out rather that turn them into the soil. It turns out that rye is great for keeping the weeds down because it has some allelopathic properties that keep them from growing. Since I was going to plant vegetable seeds in the beds I had covered, I did not want to take a chance that they might react to this residue. All went well.

Red clover detail My second try was this past winter. I planted red clover and was very pleased. When the time came to plant veggies in the bed, I whacked the clover down and turned it in, waited a month, then planted my crops. I made sure to cut it down before it flowered and went to seed. This stops the plant from taking up nutrients in the soil to store in its seed. The soil was beautiful and loose, and the clover had broken down completely. The clover did great, even with the cold and snow, and, best of all, no weeds to pull. Nice.

The takeaway lesson has been that the small investment of time and effort in cover cropping pays huge dividends. My soil was enriched with organic matter, water infiltration and water holding capacity was increased, weeds and soil-borne diseases were suppressed, plant available nitrogen was added and beneficial insects were attracted. In addition, I grew my own mulch and fertilizer. Finally, I am certain my soil, my veggies and the environment all thanked me for this effort.

So, there you go. I encourage you to give this practice a try if it fits your needs. It is inexpensive , low maintenance, and there is plenty of information on the Internet, including charts to help you choose the best cover crop for your needs and your region. Happy gardening to you all!

Resources for cover crop article:

Mother Earth News: Grow Cover Crops for the Best Garden Soil by Harvey Ussery

Mother Earth News: Use Cover Crops to Improve Soil by Barbara Pleasant

Marin Master Gardeners: Cover Crops boost soil in vegetable beds by Marie Narlock

University of California Agriculture and Natural Resources Cooperative Extension Sacramento County: Cover Cropping in Home Vegetable Gardens by Chuck Ingels

Oregon State University Extension Service: Cover Crops for Home Gardens by R.L. Rackham and R. McNeilan

Rodales’s Organic Life: Cover Crops

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