Understanding your garden needs and matching plants to your local climate will help you reap the greatest rewards. Cover crops can perform a wide range of jobs to improve your garden soil. Are you looking to add nitrogen, fight pests, or stabilize erosion-prone soils? Use this guide to identify the best cover crops for a thriving garden!

Part 1: Problem-Solving Cover Crops

Cross-section of subsoil showing the layers beneath the ground surface
Bare, unplanted soils are at risk of losing valuable nutrients, making it hard for the next plant in that spot to be healthy. Cover crop root systems and plant matter (both alive and dead) can help to keep soils vital and loosely textured.
Healthy, dark soil with earthworms
Cover crops add organic matter to soil, which offers food and habitat to earthworms and other "soil critters." Living soil helps air, water, and nutrients make their way to plant roots with ease, which improves plant growth!

1. Cover Crops To Provide Nitrogen

Cover crops add nitrogen to soils through one of two methods: nitrogen fixing and nitrogen scavenging. Nitrogen-fixing legumes such as clover, vetch, and peas convert atmospheric nitrogen into forms that can be used by your plants. Nitrogen-scavenging plants capture excess nitrogen before it can run off and store it in plant tissues. Excellent nitrogen scavengers include radish, rye, sudangrass, and sorghum-sudan hybrids. Grains are also good scavengers.

2. Cover Crops To Improve Soil Structure

One of the best cover crops for aerating compacted soils and improving water infiltration is tillage radish, or daikon radish. Clover seeds, vetch seeds, rye grass seeds, sudangrass, sorghum-sudan hybrids, and mustards all promote healthy soil structure. These cover crops produce byproducts that help soil particles adhere to one another, resulting in a good, crumbly textured soil.

3. Cover Crops To Add Organic Matter or Biomass

Organic matter provides many benefits to soils. Most cover crops provide some amount of organic matter to soils, but plants differ in the benefits they provide. Succulent plants, such as legumes (clover, partridge pea, and vetch), break down quickly in soils. They provide nutrients, but leave behind little lasting biomass. Fibrous plant tissues, such as grasses and grains, break down more slowly. They will tie up nutrients, but build stable humus, or organic matter, in soils. Perennial clovers such as white and red clover can provide both benefits, with the leaves breaking down quickly while the roots and stems contribute to biomass accumulation.

4. Cover Crops To Reduce Soil Erosion

Cover crops that provide good cover and a dense root system help stabilize soils and combat erosion. Clover seeds, annual rye grass seeds, Austrian winter peas, crown vetch seeds, sudangrass, sorghum-sudan hybrids, rapeseed, mustards, and cowpeas are good cover crops for erosion protection.

5. Cover Crops To Manage Pests

Some cover crops produce compounds that help fight soil-borne pests, while others are excellent at attracting beneficial insects. Here are a few pest-fighting plants:

  • Crimson Clover: Blooms to support beneficial insects.
  • Buckwheat: Supports large populations of beneficial insects and pollinators.
  • Cereal Rye: Reduces soil-borne diseases and root-knot nematodes. Not suitable for crops impacted by cutworms and wireworms.
  • Wheat: Suppresses diseases and nematodes.

6. Cover Crops To Suppress and Control Weeds

Cover crops suppress weeds by preventing seed germination, through competition, or by producing a chemical deterrent in the roots, called allelopathy.

  • Seed Germination: Hairy vetch, buckwheat, and daikon or forage radish reduce light penetration into soils, which suppresses weed seed germination.
  • Competition: Dense-growing cover crops and those with aggressive root systems manage weeds through competition. Choose peas, clovers, buckwheat, rye, and oats.
  • Allelopathy: Buckwheat, brassicas including mustards and radishes, sorghum and sorghum-sudangrass hybrids, and subterranean clover produce allelopathic substances. Winter rye is effective against pigweed, lambsquarters, purslane, and crabgrass. Some crops such as lettuce are sensitive to allelopathy, while others benefit, so use with caution.

7. Cover Crops To Improve and Manage Nutrients

Nitrogen is not the only nutrient managed through cover crops. Cereal rye is excellent for nutrient cycling. Buckwheat and brassicas improve availability of phosphorus in soils. Though known for nitrogen fixation, legumes such as clover, vetch, and partridge pea also help cycle phosphorus in soils.

8. Cover Crops To Provide Lasting Residue or Mulch

Crop residues from yellow blossom clover, rye grass (Lolium), winter rye (Secale cereale), sudangrass, sorghum-sudan hybrids, and barley provide a long-lasting mulch to suppress weeds and conserve soil moisture.

Part 2: Cover Crops To Meet Your Needs

1. Cover Crops For Your Gardening Timeline

Like vegetables, some cover crops are better suited to cooler growing seasons while others thrive in the summer heat. Winter cover crops are widely used to protect and condition soils during the fallow cold season. Warm-season cover crops are commonly used in the spring or summer to balance soil nutrients between other crops. Use the following list to select cover crops according to the time of year.

2. Cover Crops Based On Growth Rates

Plant biology is another factor affecting cover crop selection. Some crops are fast-growing and perfect for quick cover between other crops. Others are perennial, providing an excellent living mulch. The following traits can help guide you in selecting an appropriate cover for your unique situation.

  • Growth Rate: Buckwheat, berseem clover, Austrian winter pea, annual ryegrass, and oats are all fast-growing crops ideal for providing quick cover between crops or on sensitive sites.
  • Annual vs. Perennial Cover Crops: While most cover crops are annuals, there are a few perennials commonly used for living mulch, erosion control, or biomass production. These include medium red clover, crown vetch, and vernal alfalfa.
  • Winter-Killed vs. Winter-Dormant Fall-Planted Crops: Not all crops that we consider "winter cover crops" actually produce during the winter. Many are "winter dormant," surviving the cold and resuming growth in early spring, when they put on the bulk of their biomass. Others are "winter killed," meaning the plants die in winter but continue to stand, providing soil protection and preventing erosion from wind or rain. Which group a crop falls into depends on your climate, since a crop that is winter killed in a cold region may survive the winter in a milder one.
    • Winter-Killed Crops: Oats, spring barley, and oilseed or forage radishes put on fall growth that protects soils, then die back once winter temperatures arrive. Radishes also penetrate soils, providing aeration, and their tissues decompose over the winter months, leaving a clean seed bed for early-season spring crops.
    • Winter-Dormant Crops: Winter rye, winter wheat, triticale, and spelt are very cold hardy and survive winter in most regions. Hairy vetch, crimson clover, and Austrian peas also go dormant during the winter months in locations where the plants are winter hardy. Fall planting provides an initial surge of growth, yielding roots that help hold soils over the winter.

3. Cover Crops For Termination Methods

After the role of a cover crop has been filled, plants are generally terminated or killed to prepare planting beds for the main crop. Crop termination also returns nutrients and biomass to the soil. Many cover crops are terminated to prevent them from going to seed and becoming weedy.

Understanding how a cover crop will be terminated or killed is critical to plant selection. Some cover crops used in large-scale farming operations are killed using herbicides, but this is obviously not an option for organic gardeners, and one we don't generally recommend. Before planting a cover crop, know how to terminate its growth cycle and select crops that fit your termination plans. Following are common techniques used for different crops. Also note that timing can be critical in terminating certain crops such as ryegrass.

  • Cutting, Mowing, and Lopping: Depending on the size of your cover crop planting, you may use a lawn mower, string trimmer, hand shears, or pruners to cut the crop to the ground. Most cereal grains, buckwheat, and peas can be managed by cutting. Cut material can be used to mulch beds, composted, or tilled into the soil.
  • Winter-Kill: Winter-killed crops can be tilled into the soil, cut and used as a mulch, or plants and seeds can be directly sown or transplanted into the standing crop residues. With the latter method, be sure to consider the light needs of seeds. Lettuce, for example, requires a clean seed bed. In colder regions, winter-killed crops include oats, spring barley, radishes, field peas, berseem clover, and frost-tender warm-season crops such as buckwheat, cowpeas, soybeans, sudangrass, and sorghum-sudan hybrids.
  • Tillage: Low-growing white, red, and berseem clover seeds can be terminated by tilling into the soil. Annual rye grass is also commonly managed with tillage.

4. Cover Crops Suitable To Your Region

As with any crop, it is important to match cover crops to your winter hardiness zone. Some cover crops may be winter-killed in one region but go dormant in warmer climates. Likewise, plant hardiness varies by region, including both cold and heat tolerance.

American Meadows' cover crop product pages include information on the ideal regions to grow each species as well as USDA hardiness information.

Have questions? You can always contact us for recommendations and advice for planting the right cover crops.

Share this post:
Tags:
How To Choose