Why Clover is the Best Winter Cover Crop for Your Garden

You can’t deny the benefits of cover crops once you see the results in real time. Growers should strategically plan a rotating blend of legumes, cereals, and brassicas to improve soil fertility, structure, and organic matter. 

Cover crops in the legume family, including clover, affix nitrogen to their underground root nodules, making it available to future crops and boosting your garden’s productivity and yields. It also lowers your dependence on external nitrogen fertilizers. Clover is an excellent option for a nitrogen boost, soil coverage, and reduced weed germination in the spring.

Winter conditions pose severe risks to bare soil, including soil erosion, runoff, and damage from snow, hail, and animals passing through. Clovers are an excellent ground cover. They help your soil stay put, are cold-hardy, and will provide much-needed food to early spring pollinators. 

Related: Top 5 Benefits of Using Cover Crops in Home Gardens 

Benefits of Using Clover as a Winter Cover Crop

Members of the legume family affix nitrogen to nodules formed within their root system. Nitrogen fixation occurs when clover creates a symbiotic relationship with Rhizobium bacteria that live near the root system. The clover provides carbohydrates to the bacteria, and in turn, the bacteria take ammonia from the air and convert it into a form plants can use to make protein and grow. Nitrogen fixation also reduces nitrogen leaching into nearby water systems and soil. To learn more about how legumes can transfer nitrogen to nearby plants underground, read “Red clover varieties show nitrogen fixing advantage during the early stages of seedling development,” published by the Canadian Journal of Plant Science. 

The combined thick taproot and the less dense fibrous roots of legumes improve the soil structure. The debris breaks down quickly, water retention increases, and soil compaction decreases. 

By using clover cover crops, growers can reduce the need for harmful chemical herbicides like glyphosate to control unwanted weeds and other vegetation. Its dense mat-like ground cover will suppress undesirable growth while reducing run-off and erosion. 

Pro tip: Microclover is gaining popularity as a living mulch around gardens, as a lawn alternative, and in pathways instead of mulch or wood chips. The microclover can tolerate foot traffic, suppress weeds, and affix nitrogen to nearby plants. 

Types of Clover Suitable for Winter Cover Cropping

Let’s discuss the top three clovers that are beneficial as winter cover crops. 

Crimson Clover (Trifolium incarnatum L.)

Crimson clover is an annual, herbaceous clover that boasts a gorgeous deep red, 1 to 2 ½ inch flower atop hairy stems that grow one to three feet tall. The leaves are round-tipped, and the plant grows rapidly. 

Seeds for this type of clover are larger and a bit more expensive than others, and while it may winter-kill in harsh regions, some see this as a positive aspect. The plant debris will continue to protect the soil surface, begin to break down, and add fertility, and your spring fields will be easier to work in. 

Seeding rates are 12 to 20 pounds per acre, with the lower end being more suitable for cool regions. Seed crimson clover early to mid-August to ensure it doesn’t go to seed in the fall and reappear in the spring—disk in broadcasted seeds. This variety is excellent when used in between plantings of vegetable crops or between berry rows. It will perform best in mild climates without extreme fluctuations. Crimson clover requires at least 30 inches of rainfall or irrigation for proper growth. 

Crimson clover's annual fixed nitrogen can be 50 to 150 lbs. per acre, saving you money and reducing your dependence on fertilizers. 

White Clover (Trifolium repens L.)

You’ve likely seen white clover popping up in yards or used as a lawn alternative across all regions. It grows low and features dense foliage of trifoliolate, medium green leaves with light green chevron markings across the center. Rosette-like flowers are cream-colored with a pink or red watermark. Because of its creeping growth pattern, white clover is an outstanding ground cover. A strong stand will help suppress weeds and reduce wind and rain erosion. 

This perennial legume is easy to grow because of its tolerance to acidic and alkaline soils, some flooding, and poorly draining soil, even doing well in clayey or sandy soils. It will do best in cool, moist regions. Be aware white clover doesn’t perform well in droughts, so use it in areas that will receive ample irrigation for the best results. It will not be the best option for growers who experience cold winters but little snow. 

Sow white clover in late summer or early fall at least six weeks before the first anticipated frost. Prepare the soil by adding high phosphorus, potassium, and sulfur levels required to thrive. Broadcast two to four pounds per acre for a stand of white clover or seed in rows using one to three pounds per acre. 

Red Clover (Trifolium pratense L.)

Red clover isn’t the best name for this pinkish-purple and short-lived perennial. It’s great for colder climate growers because it can tolerate temperatures near 15°F (-9.4°C) and is hardy in USDA zones 3 to 9. Interestingly, red clover is relatively drought-resistant and can go a few days without water. Check with local authorities, as red clover is considered invasive in some areas. 

A strong stand of overwintered red clover can produce between 70 and 150 pounds of affixed nitrogen per acre. Use 15 pounds per acre for a strong stand of pure clover. Use 8 pounds if mixing with grass seed. Growers effectively use it as a legume before summer-planted corn or vegetables. The Michigan State University says red clover is the most commonly used and profitable cover crop. It is often used with oats and may suppress spring allergies caused by ragweed. 

Seeding Rates for Clover in Market Garden Rows

How to Plant Clover for Winter Cover

To prepare your gardens for winter cover crops, remove all weeds to ensure as little competition as possible. After soil testing, work the amendments in if the results call for them. The pH level should be between 6.0 and 7.2 and never below 5.5. Have an irrigation management plan in place. Clover prefers well-draining soil but will tolerate wet spots for a short period and poor fertility with the help of fertilizer. 

Seed depth is extremely important for successful germination and growth. Sow seeds no deeper than ½ inch and use an inoculant to ensure the desired outcome of nitrogen fixation. If you notice low germination rates, you may have seeded too deeply. Your timing will depend on your growing zone and the type of clover you choose. In general, seeding should occur in late summer to late fall. Find your first frost date to help you count backward to your ideal sowing date. 

Managing Clover Cover Crop

Winter Kill and Its Benefits

Winter-kill cover crops die when temperatures reach a certain threshold or a hard frost occurs. Growers get the added biomass and soil protection in the winter months and annual weed suppression in the spring from the debris. 

When planted in early spring, clover reduces weeds, attracts beneficial insects, improves soil tilth, and increases soil organic matter (SOM) levels. It will require a termination method though since there will be no frost to kill the cover crop back. 

Related: Cover Crops for Successful Land Management | Fall Cover Cropping

Termination Methods

Roll, crimp, or mow down the clover in a no-till system. Grazing is an option if you have animals, mainly cattle or rabbits. Leave the debris in place to allow the plant residue to add to the SOM levels and nitrogen boost. After terminating the crop, use a 6-mil silage tarp to promote and speed up the breakdown of debris in preparation for a stale seedbed. No-till growers may plant the next crop directly into the debris, allowing it to serve as mulch. 

Farmers who use tilling can mow their clover down and till the plant debris to incorporate it into the soil. Wait about three weeks to plant your next crop so the nitrogen can become available. 

Comparing Clover with Other Winter Cover Crops

Now, look at other popular winter cover crops and how they score against clover. The cost of cover crop seeds depends on the type and size of the seed, the seeding rate, general management, and termination plan. These factors affect the overall cost of cover cropping, which varies. The price will also depend on your area and retailer.

Clover vs. Rye

Where clover enhances your future crops by affixing nitrogen, rye will absorb excess nitrogen in the soil as it grows. Both will prevent soil erosion and reduce topsoil loss to runoff. Planting them together in regions where clover may winter-kill allows growers to take advantage of all the benefits. Rye will continue to grow through winter, and the perished clover debris will cover the space between the rye plants. 

Early establishment is crucial to getting the height and bulk you need before winter temperatures slow down the rye’s growth to provide biomass benefits. It should be at least 12 inches tall before a frost arrives. To avoid regrowth, terminate rye before seeds form and remove the debris from the garden. No-till growers may have difficulty getting rye to completely die back and keep it from re-seeding. 

Clover vs. Vetch

Where clover can be winter-killed, vetch is extremely winter-hardy and can tolerate temperatures down to -20°F (-29°C), continuing to grow and anchor itself in place with its robust root system. Vetch provides ample phosphorus, unlike other cover crops, and improves the soil structure. Its biomass breaks down quickly upon termination, releasing nutrients into the soil. 

Clover vs. Mustard

Both clover and mustard are great for weed suppression and ground cover. Broadleaf mustard has the unique benefit of possessing glucosinolate, a chemical compound known to help control various pests like soil nematodes and diseases like Phytophthora blight. Mustard can be grown as a winter cover crop for erosion and weed control, terminated, worked into the soil, and used as a biofumigant. Read more about how to lower your chemical fumigant use and learn about mustard as a cover crop from the Integrated Pest Management University of Missouri.

Be aware that flea beetle and cabbage aphids love mustard, so if you plan to overwinter them as a cover crop, especially in a high tunnel, this may be a challenge. 

Related: Greenhouse Covers & Shade Cloths

Frequently Asked Questions

What is the best time to plant clover as a cover crop?

Clovers germinate best when soil temperatures are cool and moist, around 38° to 42°F (3.3 to 5.5°C). You can also frost seed clover onto frozen ground when spring snow melts. It will soften as spring arrives and germinate when ideal conditions present themselves. 

How does clover improve soil health?

As a member of the legume family, clover affixes nitrogen and makes it available to the subsequent crops. It also covers the soil well, making it an excellent option for growers with harsh winters who want to avoid soil erosion, improve soil organic matter, and suppress spring weeds. 

Can clover be used in conjunction with other cover crops?

Combining clovers with a cereal variety or annual ryegrass ensures the soil remains covered if clover winter kills and enhances each benefit. 

What are the common challenges of using clover as a cover crop?

If not managed, white and sweet clover can become invasive. When using crimson clover, its spring growth or re-growth is fast and furious, so growers should have a management plan for termination in place. 

How do I terminate clover effectively?

Clover can be mowed, “chopped-and-dropped,” crimped, rolled, or tarped. Leave the debris in place so it can contribute to organic matter levels.