Freezing winter weather, hot summer sun, and high temperatures can wreak havoc on the soil in vegetable gardens. Cover crops for gardens not only protect the soil from weather extremes, but are also used between crops to restore fertility, suppress weeds, or to protect or restore a garden bed left unplanted for a season. They can also be used to reduce fertilizer use, restore or trap nitrogen, and improve soil and water quality.
Before the invention of synthetic fertilizers, cover crops were planted in between harvests to scavenge and store nitrogen and other elements, preserve soil structure, slow water runoff and evaporation, protect garden beds from erosion, and suppress weed growth. It’s a sustainable method overlooked by many home gardeners but is widely used in organic agriculture.
Many gardeners see Fall as the end of the gardening season – they pick the last of their tomatoes, peppers, and beans and put a lid on it. But Fall is a critical season for your vegetable garden beds, as they need to be protected from the coming winter weather. You’ve probably also seen what harsh summer weather does to open spaces between your vegetables – cracked, dry, hard-baked soil. The best way to protect your garden beds from these weather extremes is by planting a cover crop, also known as “green manure”.
What are examples of cover crops?
Cover crops are primarily legumes, grasses, and brassicas and include oats, buckwheat, vetch, beans, peas, daikon radishes, tall fescue, winter peas, forage radish, mustards, clover, barley, ryes, sudangrass and many more. Which cover crop you should plant depends on your region and purpose: protecting beds from erosion, suppressing weeds, or restoring fertility.
Planning is key in cover cropping, as you need to give the plant sufficient time to perform its function (note that some seeds can overwinter and grow in the following spring). Time of year is also important. For instance, clover seed must be planted mid to late summer to give it enough growth to establish before the onset of winter.
Cover crops are planted at different points in the gardening cycle – some in spring, some in winter, some in fall, but the intent is to let them grow until they winterkill or until the next planting cycle when they are tilled into the soil to provide nutrients, serve as a mulch layer and/or to increase soil tilth. Certain deep-root cover crops are excellent for breaking up compacted soil as they create passageways for air and water as their root systems decompose.
Daikon Radish breaks up clay soil
For instance, Daikon radish, grown largely for its use in Asian cuisine, not only protects the soil with its generous foliage but its long taproot – sometimes 3 feet or more – is highly effective in breaking up clay soil when left in place to decompose. Daikon Radish seeds germinate quickly and the radish grows surprisingly fast, reaching maturity in 60 days. The taproot’s deep penetration is remarkably effective in loosening compacted soil, creating lots of paths for air and water. That makes for an environment that earthworms and other soil organisms love. Plus its foliage casts a wide shadow, making it a marvelous weed suppressant. I’ve used Daikon Radish as a cover crop several times and it really does work as advertised.
The choice of a cover crop depends on:
- what was planted in the soil bed most recently
- your geographic region
- condition of your soil (compaction, fertility, etc.)
- what you’ll plant in the same bed next season
- recent disease or pest problems
Uses for cover crops
- Fix nitrogen
- Trap nitrogen
- Soil protection from erosion
- Soil improvement (tilth)
- Weed suppression
- Alleviate soil compaction
- Reduce nematodes
- Attract beneficial insects
Best practices for cover cropping
Most gardeners typically use cover crops to protect their garden beds from winter weather to prepare for spring crops; or from summer weather before planting a fall crop. To be safe, use a combination of cover crop seed to cover all the bases: weed suppression, restoring and maintaining fertility, restoring soil tilth, and protecting soil from erosion. By planting combinations of cover crops, you will likely have at least one of the cover crops growing successfully. Sample combinations are below, but many different combinations are available.
- Annual ryegrass and crimson clover
- Radish, crimson clover and annual ryegrass
- Radish and annual ryegrass
- Radish and crimson clover
- Radish and oats
- Crimson clover and radish
- Red, ladino, and sweet clover
- Annual ryegrass, crimson clover, red clover, radish, and sweet clover
- Hairy vetch and oats
- Cereal rye and hairy vetch
- Triticale and annual ryegrass
- Peas, oats, and hairy vetch
Cover Crops By Region, United States
Legumes fix nitrogen, improve soil organic matter and soil structure, and prevent erosion. Legumes typically grow slower than grasses.
Most grasses scavenge nitrogen, improve soil organic matter and soil structure, prevent erosion and provide forage. Grasses have relatively quick growth.
Brassicas prevent erosion, suppress weeds and soilborne pests, break up compacted soil, and scavenge nutrients.
|California and West||Bell Beans, Fava Beans, Field Pea, Lentil, Lupine, Medic Mix, Subterranean Clover, Sweetclover, Balansa Clover, Berseem Clover, Crimson Clover, Persian Clover, Red Clover, Rose Clover, Wooly Pod Vetch, Common Vetch, Hairy Vetch, Purple Vetch, Cowpeas, Chickpea, Sunnhemp, White Clover||Barley, Annual Ryegrass, Sudangrass, Buckwheat Annual Fescue, Cereal Rye, Triticale, Wheat, Flax, Japanese Millet, Proso Millet, Sorghum, Teff,||Mustards, Daikon Radish, Forage Radish, Tillage Radish, Japanse Radish, Rapeseed|
|Southwest||Lespedeza, Medic Mix, Subterranean Clover, Cowpea, Sesbania, Lablab, Hairy Vetch, Common Vetch, Crimson Clover, Berseem Clover, Arrowleaf Clover, Yellow Sweetclover, Red Clover, Alfalfa, Austrian Winter Pea, Lablab, Sesbania,||Barley, Buckwheat, Sudan Grass, Sorghum-Sudangrass, Forage Sorghum, Pearl Millet, Annual Ryegrass, Cereal Rye, Wheat, Oats, Triticale, Foxtail Millet,||Mustards, Turnips, Forage Radish, Rapeseed|
|Midwest||Crimson Clover, Berseem Clover, Red Clover, White Clover, Hairy Vetch, Cowpea, Field Pea, Winter Pea, Soybeans, Alfalfa||Barley, Annual Ryegrass, Winter Cereal Rye, MIllet, Sudan Grass, Sorghum-Sudangrass, Buckwheat, Oats, Wheat, Triticale,||Mustards, Daikon Radish, Forage Radish, Oilseed Radish, Tillage Radish, Rapeseed, Forage Turnip,|
|Pacific Northwest and Northwest||Crimson Clover, White Clover, Red Clover, Peas, Wooly Pod Vetch, Hairy Vetch, Common Vetch, Austrian Winter Pea, Fava Bean, Bell Bean,||Barley, Cereal Rye, Annual Ryegrass, Sudan Grass, Sorghum-Sudangrass, Oats, Winter Wheat, Buckwheat,||Mustards, Daikon Radish, Oilseed Radish, Canola,|
|Mid-Atlantic||Crimson Clover, Red Clover, White Clover, Hairy Vetch, Cowpeas||Annual Ryegrass, Sudangrass, Rye, Buckwheat, Oats, Sorghum- Sudangrass, Triticale||Mustards, Daikon Radish, Forage Radish, Oilseed Radish, Tillage Radish, Rapeseed|
|Northeast and New England||Alfalfa, Alsike Clover, Red Clover, Sweet Clover, White Clover, Hairy Vetch, Soybean, Cowpea,||Annual Ryegrass, Sudangrass, sorghum-Sudangrass, Winter Rye, Cereal Rye, Oats, Buckwheat, Japanese Millet, Teff||Mustards, Daikon Radish, Forage Radish, Oilseed Radish, Tillage Radish, Rapeseed|
|Southeast||Crimson Clover, Arrowleaf Clover, Hairy Vetch, Lespedeza, Peas, Cowpeas, Caley Pea, Perennial Peanut, Armex Lupine, Sunn Hemp||Annual Ryegrass, Rye Sudangrass, Oats, Wheat,||Mustards, Daikon Radish, Rapeseed|
Sources: Penn State Extension, Old Farmer’s Almanac, Cooperative Extension System, USDA-Cover Crops for the Southeast, New England Vegetable Management Guide, University of Minnesota Extension, Washington State University, New Mexico State University
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