Cover crops have been used for thousands of years and have seen a resurgence in recent years. While we usually think of cover crops in production agriculture, they can also be used in home gardens. By keeping living plants growing in the soil when vegetables are not, gardeners can build healthier, more productive garden beds over time.

What are cover crops?

A cover crop is a plant grown primarily to benefit the soil rather than for harvest. They can be used in a variety of ways, such as protecting bare soil, increasing soil organic matter, suppressing weeds, scavenging nutrients, and improving soil structure. Some cover crops can even add nitrogen to the soil for future crops.

Keeping roots in the ground helps support beneficial soil organisms and improve soil structure. While cover crops are not an instant solution for poor soils, using them consistently over time can lead to improvements.

Types of Cover Crops

Most cover crops fall into three groups:

Grasses, such as cereal rye and oats, produce extensive root systems and large amounts of biomass. They are especially useful for weed suppression, erosion control, and building organic matter.

Legumes, such as crimson clover and field peas, form a symbiotic relationship with nitrogen-fixing bacteria to capture atmospheric nitrogen and convert it into a form plants can use, helping improve soil fertility.

Brassicas, such as tillage radish and turnips, can produce deep taproots that help break up compacted soil, improving water infiltration and bringing nutrients from deeper in the soil closer to the surface.

Choosing and planting cover crops

Before selecting a cover crop, consider what problem you are trying to solve. Are you looking to add nitrogen, suppress weeds, improve soil structure, reduce erosion, or increase organic matter? Different cover crops provide different benefits. If you’re trying to achieve multiple goals, consider using a cover crop mix.

Many gardeners start with cool-season cover crops. Popular options include cereal rye, oats, crimson clover, field peas, and tillage radish. Some species, such as oats, peas, and tillage radish, are winter-killed. Others, such as cereal rye and crimson clover, survive winter and must be terminated in spring.

When planting cover crops, good seed-to-soil contact is important. Lightly raking the soil before seeding improves seed-to-soil contact and germination. Seeds can be broadcast by hand or with a spreader. After planting, make sure plants have adequate water to establish successfully.

Terminating cover crops

If cover crops aren’t winter-killed, they will need to be terminated before planting your desired crop. Termination methods include mowing, crimping, cultivation, tarping, or incorporating the plants into the soil. Timing is important; cover crops should be terminated before they produce seed to prevent them from becoming weeds themselves.

After termination, allow two to three weeks before planting. This allows plant residue to begin decomposing and reduces the chance that nutrients, particularly nitrogen, become temporarily tied up during decomposition.

Potential challenges

Like any gardening practice, cover crops have drawbacks. Added residue can make direct seeding more difficult and may provide habitat for pests. Despite these challenges, cover crops are one of the most effective tools gardeners can use to improve soil health over time.

Good Growing Tip of the Week: Cover crops can also be planted for summer use. Warm-season cover crops, such as buckwheat and cowpeas, are planted in spring or summer and grow rapidly during warm weather.

By Ken Johnson, Horticulture Educator, University of Illinois Extension