The floor should not be left open. While vast, empty fields, torn from the ground and waiting to be planted, may seem like the essence of American agriculture, bare soil is not part of Earth's natural growth cycles. In fact, the healthiest soil is covered with plants that grow year-round.
Faced with the harmful effects of conventional cultivation, such as soil erosion, compaction and fertilizer runoff, the agricultural industry has turned to sustainable agricultural practices such as cover cropping.
Many home gardeners rely on growing cover crops as an effective and economical way to protect and enrich their soil between growing seasons rather than leaving it bare in winter. After all, what gardener wouldn't want a simple, inexpensive way to keep their garden safe to enrich the soil, suppress weeds, increase yields and prevent nutrient loss?
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What are cover crops?
Cover crops are plants planted between growing seasons to protect soil, prevent erosion, and conserve nutrients. In agriculture, farmers plant non-cash crops to cover the soil after harvesting. During the winter or fallow period, these cover crops create a living mulch that protects the soil from wind and water erosion and suppresses weeds. In the spring, the farmer turns cover crops into "green manure," providing organic matter and nutrients to enrich the soil for future crops.
Garden cover plants differ from ground cover plants primarily in terms of their purpose. Cover crops are grown to improve soil health and fertility (not necessarily for food or to look pretty), and ground covers are generally low-growing plants used for landscaping purposes, to fill gaps, to control weeds in ornamental gardens, and to remove or replace grass. These perennial cover crops act as living mulch, suppressing weeds as the garden grows. They can also help retain water and enrich the soil.
Although growing cover crops has been a common practice for thousands of years in agricultural history, their use fell out of favor in North America in the 1950s when synthetic fertilizers, herbicides, and chemical pesticides became widespread. In the late 20th century, cover crops returned as one of the shining stars of sustainable agricultural practices for home farmers and gardeners.
Benefits of green manures
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It is not surprising that our ancestors used covers to improve agriculture. The benefits of cover crops and their green manures are many and accessible to home gardeners, whether they have a large farm or a container garden. Garden cover crops, in particular, help restore soil health after a season of nutrient deficiency by growing edible plants.
Erosion Control: Cover crops protect soil from wind and water erosion, protect topsoil and reduce runoff.
Improve soil structure: Cover crops improve soil structure by breaking up compacted soil, allowing better root penetration.
Improve aeration: The roots of cover crops improve aeration by creating channels in the soil, improving microbial activity and soil fertility.
Nutrient Enhancement: Cover crops (such as legumes) enrich the soil with nitrogen and other nutrients by fixing and accumulating biomass, thereby increasing soil fertility.
Conserve water: Covering crops not only reduces runoff, but also improves filtration and conserves soil moisture.
Disease and pest control: Some cover crops (such as mustard) act as biodisinfectants by reducing fungi and controlling parasitic nematodes.
Weed Control: Cover crop planting creates a dense stand of growth that suppresses weeds and other unwanted plants.
Supporting biodiversity: Cover plants provide habitat for insects, birds and soil organisms.
Financial benefits: Cover crops can increase productivity and reduce the need to purchase fertilizers and herbicides.
Related: What is no-dig gardening and why should you try it this spring?
The best cover plants for the home garden.
Cover crops are generally divided into three categories: legumes, hardwoods, and cereals. Each has its own advantages and characteristics.
legumes
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Legumes such as alfalfa, peas, chickpeas, and peanuts are nitrogen-fixing cover crops due to their symbiotic relationship with rhizobia bacteria living in their roots. These bacteria convert nitrogen from the air into a form available to plants. Gardeners may need to inoculate legume seeds with soil bacteria if they have not been pre-treated.
Legumes contain more nitrogen than grasses, so they break down faster and release nitrogen and other nutrients more quickly than grains and hardwoods. In addition, they provide excellent weed control. Legumes also attract wildlife. So, if deer are considered garden pests in your area, you may want to consider another product.
Ideal for: Enriching soil with nutrients for future crops.
Our recommendation: Outsidepride Crimson Clover Legume Seeds for $24.99 at Amazon
Non-GMO purple clover seeds produce masses of fast-growing red-flowering legumes that add nitrogen to the soil and prevent runoff and erosion.
Grain
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Grain cover crops include annual grasses such as oats, rye, and wheat. They have a large root system, which makes them great for reducing erosion and water runoff. These plants are particularly effective at fixing nitrogen, meaning they capture nitrogen from the soil, incorporate it into plant biomass, and return it to the soil when the plants turn it into green manure. They also produce more biomass than other plants, meaning soil organic matter increases significantly.
Ideal for: adding biomass and protecting soil from erosion and nutrient leaching.
Our recommendation: Don't plant winter rye seed for $22.91 at Amazon
This winter rye seed is non-GMO and open pollinated. With a fibrous root system that improves soil drainage and protects plants from wind and water, winter rye is an ideal cold-weather crop and one of the best cover crops for storing nutrients.
broad leaves
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Broadleaf plants have relatively broad leaves compared to the narrow or grassy leaves of cereals. These include buckwheat, flax, mustard, annuals such as alder and brassicas such as daikon radish. The broad leaves grow quickly and have deep, penetrating roots that help break up clay and compacted soil. Some plants also act as biofumigants, suppressing soil pests and diseases and attracting beneficial insects. Some types of cabbage smell like rotten eggs when they rot. If your house or neighbor is downwind of your garden, take this into account.
Ideal for: Improving soil structure and preventing weeds.
Our Recommendation: Yellow Cap Mustard Seeds from Johnny's Selected Seeds $22.35
Yellow mustard provides fast-growing plant masses that suppress weeds and prevent soilborne pathogens and pests. Their deep roots loosen compacted soil and provide aeration.
Seed mixes
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High-quality cover crop seed mixes include seeds from many green manure crops that provide different benefits and complement each other. Seed mixes can be a great choice for beginners or those wanting a cover crop for raised beds or containers. You can buy a ready-made seed mix or make your own.
Ideal for: All-round maintenance and improvement of soil health in gardens and raised beds.
Our recommendation: Uncoated Garden Seed Mix for $28.59 at Amazon
A blend of nine popular cover crops including legumes, grains and cabbage, this seed mix provides diverse cover, enrichment and soil protection.
Related: 9 Reasons to Plant Fall
How to plant cover crops
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Growing cover crops successfully requires some thought and planning. Follow these steps to incorporate this smart growing method into your garden.
Consider your garden's needs and priorities. Is weed control the main concern? Or do you want to block or add nutrients? You may want to test your garden soil to get a clear idea of its health.
Consider when you want to plant your cover crops. Want to use cover crops for the winter? If so, choose legumes or grains that can germinate and grow in the cool temperatures of late fall. Need a quick mulch in the spring to revitalize the soil and keep weeds at bay before the regular planting season? Then choose a fast-growing crop, such as buckwheat, one of many warm-season cover crops. If you need garden mulch during the growing season to fill in the gaps left by uprooted plants at the end of the season, choose low-growing cover crops such as alder as an annual companion.
With these tips in mind, choose or mix a cover crop and buy seeds.
At the end of the growing season, remove wilted plants from your garden about 3-4 weeks before the risk of hard frost. Loosen the soil with a garden fork and rake it into place.
Plant a cover crop by sowing or scattering the seeds in the garden bed. Gently push the seeds into the soil and bury them. Water regularly until dry.
Watch your houseplants grow and bloom. If you plant cover crops early or have a longer growing season, you may need to prune the plants to prevent the seeds from setting.
Three to four weeks before planting spring crops, stop the growth of cover crops by mowing or cutting them and burying them in the soil. This can be achieved by shallow plowing. If you have a small garden area, such as a raised bed or container, simply use a trowel or trowel to turn the cover crops into the soil. If you prefer to sow directly, cut off the aerial shoots and allow the cuttings to dry in place for four weeks. Then sow summer plant seeds directly into the biomass.
