Cover Crops in Community Gardens

Prepared by guest contributor Samuel Garrett McKee with assistance from David Neely and Margaret Rossano. Garrett is a garden leader of the Circus-Lyons Community Garden.

Cover crops have become increasingly popular in the past several years, seeing use from large-scale producers down to mid- and small-scale operations. Originating in pre-industrial times, cover crops have been an organic and sustainable, tried-and-true, method of using naturally occurring cycles to benefit soils for hundreds of years. The benefits are clearly seen once implemented, even at the community garden plot scale (10×10 ft, for example). At the Circus-Lyons Community Garden, we have been using cover crops for the past two years with solid results.   

Essentially, when a garden plot would otherwise be unused, we “cover” that soil with a special crop of plants, the purpose of which is to feed the soil, rather than to feed the gardeners. Several weeks before you want to use that plot again for annual planting, the crop is cut down and the plant matter incorporated back into the soil. Fall is a great time to start implementing a cover crop at your garden. Read on for more information and detailed advice.

cover crop planted in October that survived the winter and is growing well in February
Feb. 3, 2019. Cover crop planted in late October, cereal rye, Austrian winter peas and crimson clover. Established before coldest weather hit, overwintering well even with a real winter.  It’s merely waiting for longer warmer days and will likely be a foot tall by April 1.

The amount of information on cover crops can be daunting when you first begin the research, however, clarity can be found by thinking of cover-cropping as reminiscent of natural cycles. Central Missouri was once home to native tall-grass prairie ecosystems: perennial grasslands that harvest sunlight during the growing season and put the resulting carbon into plant  tissue, which is in turn harvested by grazing animals or consumed by wildfire, thus promoting plant competition and further unimpeded growth and diversification. This cycle was carried on without human intervention, adding yearly inputs to the soil.  

Typically, gardeners and farmers plant annual crops during a growing season, fertilize with off-site inputs, harvest, remove any residue of the crop, and then consider things finished. This leaves our soil more or less bare during the winter season, opening up invasion opportunities for weeds as well as the potential for erosion. This system is not reliably found in the natural world where there is continuous biological activity in the soil, year-round. This is what cover crops aim to fulfill.   

rye and clover cover crop with soil probe showing deep rich soil
Jan. 28, 2017. Cereal rye and crimson clover cover crop with soil probe showing the color you’re looking for!

Effective cover-cropping imitates a prairie system in that it provides more overall diversity and duration of biological activity to a plot. It can also stabilize soil; armor against weedy species and erosion; improve water capture/infiltration into subsoil; and improve the soil’s physical, chemical and biological makeup. Many resources exist for guidance on the matter, however, I will speak for what has worked for us at the plot level in our community garden.


Species Selection

Species used are many and again can be daunting to the beginner.  I tend to think about them in botanical terms; grasses (graminaceae), forbs (many families, but you can think of them mainly as flowers), legumes (fabaceae). 

Grasses

Species include cereal rye, oats, annual ryegrass, winter wheat and sorghum.

Pros: Grasses are competitive against weeds (including Bermuda grass!), they establish quickly and reliably, and they can be harvested for grain, mulch or hay, or even grazed. Grasses scavenge soil nutrients that would otherwise leach out or be taken up by weeds. Also, they are usually very winter hardy, easy to plant in fall and inexpensive. Species include cereal rye, oats, annual ryegrass, winter wheat and sorghum.

Cons: Grasses can easily out-compete forbs or legumes planted alongside them, detracting from overall benefits of diverse cover crop plantings. Cereal rye, upon termination, suppresses weeds and/or seed germination allelopathically in the soil, meaning that compounds released by the rye as it is killed will stifle germination of other species for a short period.  A solution to this minor issue would be to allow two to three weeks of inactivity between termination and the next planting.

cover crop planting at community garden
April 23, 2018. Cereal rye, crimson clover, winter wheat adjacent to hand tilled, just terminated cover crop

Forbs

Species include radishes, turnips, buckwheat, and sunflowers.

Pros: Forbs usually have deeper root systems that scavenge/capture nutrients in the topsoil that are unavailable to many crops. The, provide bloom and beauty, and some can be harvested for seeds or flowers, or they can be grazed.

Cons: They are sometimes slower growing or difficult to get established, and they sometimes cost more.

Legumes

Species include clovers, vetches, winter peas, black-eyed peas (cowpeas).

Pros: Legumes sequester nitrogen from the atmosphere and make it available to plants in the rhizosphere (rooting zone). They provide beauty and blooms for pollinators, and can be grazed or harvested for hay/mulch.

Cons: They are they usually slower to establish than grass, and the seed should be inoculated prior to planting. Red clover is a perennial and will persist when not desired, and vetches are semi-aggressive invaders into both urban and wild environments.


Fall Cover Crops

After the summer garden crops have played out and freezing temperatures are on the horizon, you should be thinking of cover cropping by October through mid-November.  The trick is to get the crop established and at least 4- to 6-inches tall before the harsh temperatures set in. Species that work well at this time include Austrian winter peas, crimson clover, cereal rye, winter wheat, and oats. Doing a two to four species mixture seems to work well, as each year is different and having multiple species to fill in unexpected gaps is ideal. Cereal rye, crimson clover and winter peas have been a good combo for us at Circus-Lyon garden. 

Late Winter/Early Spring Cover Crops

Similar species as work in the fall will also work from late February through March and even into early April. Snap peas could be viable for this outcome, as well, since they are a legume. We’ve even had seed sown in January warm spells that germinates in early March and grows vigorously all throughout spring. 

Summer Cover Crops

After a spring crop is harvested, you can plan to seed a cover crop into an otherwise fallow plot.  Species which work well for this would be buckwheat, mustard greens, annual sorghum, black eyed peas or anything which can handle heat, sunshine and long growing days. Buckwheat puts out a long taproot, bringing otherwise unavailable nutrients up into your plot’s topsoil as well as providing much-needed blooms for pollinators. However, if left to go to seed, buckwheat will seed your plot in many little individuals that will compete with desired crops when given the opportunity! Cowpeas (or Black-eyed peas) are a great legume choice for summer. 

buckwheat cover crop planted in summer amongst other garden vegetables
Aug. 5, 2017 Buckwheat establishment following sweet corn.

Terminating Your Cover Crop

Cover crops must be “terminated” once the time rolls around for planting of desired food crops.  Many ways exist to do this, but I will detail the way which has worked for us. First we mow or weed-eat the cover crop about two to three weeks prior to our desired planting date. We let the residue of the cover crop sit for several days after mowing, then turn it by hand into the soil using a shovel or a tiller.  Small plots are best done by hand. Be sure to break up the clods and root systems while turning it over, and try to get dead plant matter buried. This provides food for earthworms and countless other micro biota in the soil to consume and make available for your soon-to-follow food crops. Some warmer season cover crops, such as oats or buckwheat, will self-terminate, or winterkill, when exposed to cold temperatures. This is also a convenient time to incorporate compost into the soil to feed the incoming crop.  

cover crop mowed down and tilled in
March 30, 2018. Mowed cover crop adjacent to mowed, then tilled cover crop.

Optionally, legumes and forbs can be allowed to flower before you terminate them, which provides blooms for native pollinators and honey bees (crimson clover is worth growing for the flower alone!). Buckwheat seed can be harvested easily enough by hand and used the following year, or ground into gluten-free flower. Cowpeas and snap peas can be harvested for consumption.     

A good cover crop is a species that “behaves” in an agricultural setting, meaning it doesn’t escape or become invasive, is an annual, doesn’t persist after termination, and is consistent in establishing  and flowering like any other crop. A cover crop’s ability to suppress weeds is perhaps its most powerful feature, as the ideal period after termination to planting is a very short window, excluding many undesirable weed species otherwise abundant in our community gardens.


Summary

In summary, cover crops provide a suite of benefits to your garden plot including improving soil structure, fertility, water holding capacity and overall diversity; weed suppression; carbon sequestration; soil conservation; and supporting earthworms, pollinators and wildlife habitat. We have ordered cover crop seed through Wilson’s Garden Center or picked up larger custom amounts from Bourn Feed and Supply Inc., both located here in Columbia.   

Another wonderful benefit you will notice immediately is the aesthetic beauty the verdant, lush cover crops provide during otherwise dreary times of year. As the great conservationist Aldo Leopold once wrote,

“A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise.”

Cover crops can help community gardeners accomplish this simple yet powerful truth.

Tips for Watering Community Gardens

This year, the City of Columbia is raising water rates during the summer months to encourage water conservation. This may impact community gardens to a great extent. The Community Garden Coalition and others have worked with the City to successfully create an exemption to protect some community gardens from the highest water rate tier.

Regardless, we all want to make the best use of the water we use and not waste it. Following are some tips for efficient and effective use of water.

  1. Most plants need about an inch of water a week. In very hot and windy weather, they may need two inches of water in a week. Raised beds will need more water than regular garden plots. 
  2. It is best for the plants to water deeply once or twice a week. This will encourage the roots to move deeper into the ground and will make more efficient use of the water in the soil. When you are starting seeds, it will be necessary to keep the soil moist, so you may need to apply water more than once a week until the plants are established.
  3. Many of our soils in central Missouri are high in clay content. Adding organic matter will benefit plants and also increase the water holding capacity, making better use of water. Compost is one of the best ways to add organic matter.
  4. Applying water to the base of plants will make the best use of water. Ideally soaker hoses or drip irrigation is the most efficient, but that is not practical in most of our community gardens. Directing water to the base of plants will help in water conservation. It will also keep water off the leaves of plants and reduce the chances of diseases.
  5. Watering in the morning is better than watering in the evening as leaves of plants will have a chance to dry off during the day and will reduce disease development.
  6. Mulching plants will help conserve water. Leaves and grass clippings and straw make good mulch and can be turned into the soil in the fall to improve organic matter. The Community Garden Coalition provides some straw during the season. (Ask your garden leader if you don’t know how to obtain straw.)
  7. To make watering easier, group plants that require the most water together. These include lettuce, spinach, broccoli, tomatoes, peppers and cabbage. Group plants that require less water together. These include beans and corn.

At some gardens, there have been times where water was left on all night, soaking the garden plot and running onto other plots. This is very wasteful and we hope you will make an effort to see that this doesn’t happen at your garden. If you find water left on and unattended, it’s best to turn it off.

Water is essential for plant growth. The CGC and garden leaders want you to be successful in growing your garden and encourage you to use the amount of water needed for plant growth. Following proper watering techniques will result in the best plant growth and production.

Prepared by guest contributor Don Day with assistance from members of the Community Garden Coalition board of directors. Don is a garden leader of the Broadway Christian Church Community Garden

When to Plant Your Warm Season Vegetables

When should you plant your warm season vegetables?

This weekend, May 11 and 12, the Community Garden Coalition will offer warm season plants like tomatoes and peppers to gardeners. See times and other details.

So, we thought we’d take a moment to explain why we chose a date in mid-May despite some long periods of warm weather in April.

Weather in Mid-Missouri is highly variable, as anyone who has lived here for more than a month knows! When gardening experts discuss freeze dates for our area there are two critical time periods. The first is the average frost-free date. The second is the final frost-free date.

Although these dates shift over time, a recent report by Pat Guinan the state climatologist lists April 10 as the average frost-free date for Boone County. However, local factors can impact this. For instance, valleys tend to be cooler than hilltops, and urban gardens are usually warmer than rural ones because all the concrete holds the temperature higher.

The latest frost on record in Columbia was May 9, 1906. That may seem like a long time ago, but we were close to freezing this year on April 27. We want to give our gardeners, especially eager new ones, the best chance for success. Distributing sensitive plants a little later can avoid the sad circumstance of a late frost killing everything.

garden plants protected wih buckets and sheetsHere’s what my vegetable garden looked like in preparation for the cool weather at the end of April. As an experienced gardener, I am a gambler and my heirloom tomatoes were getting too big for my indoor pots. As you can see, protecting those transplants from frost was a lot of work, and not many gardeners are up to that sort of challenge—material and time wise.

Another consideration is that many warm season plants, especially eggplant and peppers, don’t like “cold feet.” They want warm soil to send their roots into, and can become stunted and drop their flowers when temperatures dip below 50 degrees.

It’s always a guessing game to pick the optimum time to plant in mid-Missouri, but these are some of the factors we try to balance when we plan our events. Hopefully the warmer weather will hold for the rest of May and your garden will grow happily.

Spring Gardening Workshop March 9

Each Saturday morning, the Columbia Center for Urban Agriculture and community partners will be offering workshops for beginning gardeners at Parkade Center (the temporary home of the Farmers Market).* You can check out “Planning & Planting a Spring Garden” next Saturday, March 9 at 9 a.m. and again at 10:30 a.m.

See details and a full list of workshops here.

*Please note the location has been updated from the original posting.

Free Fruit Tree Workshop

apple treeYou are invited to a FREE fruit tree pruning workshop at Bethel Church Community Garden (201 E Old Plank Rd.) February 19 at 4 pm. Come learn from Jim Quinn, MU Extension horticulturist about how to get the most out of your fruit trees with pruning.

No RSVP or registration required. In case of bad weather, the back-up date is Feb 22.

Free Gardening Forum

Alice LongfellowHere’s another great, free opportunity to expand your gardening knowledge in the off-season. The local Discovery Garden Club and the Columbia Public Library are sponsoring a forum with Alice Longfellow and Ann Wakeman.

Winter Garden Forum
Sunday, January 31 › 1:30-3:30 p.m.
Columbia Public Library, Friends Room

You’ll learn about mixing edible plants with ornamentals and about Missouri native wildflowers. Light refreshments served.

Act Fast: Master Gardener Class Registration Ends Jan. 19

If you’ve thought of becoming certified as a Master Gardener, now’s your chance to register for this spring’s sessions, but act quickly because they’d like all registrations in by Tuesday, January 19. Classes start Jan. 26 and go through April. Learn more at this link.
MO Master Gardener logo

Who are Master Gardeners? Here’s what they have to say about themselves:

Master Gardeners are adults of all ages who love to garden. They are members of the community who are interested in lawns, trees, shrubs, flowers, gardens & the environment.

You don’t need to know everything about gardening; this program is all about learning and then sharing your knowledge with others through volunteer service. Check it out!