How to Grow Legume Cover Crops

Wikimedia Commons

Legume Cover Crops

Fabaceae family (various species)

vegetable

Legume cover crops are fast-growing plants from the Fabaceae family planted to improve soil health and fertility. They fix atmospheric nitrogen through symbiotic relationships with rhizobia bacteria, enriching soil naturally. Common types include clover, alfalfa, vetch, and field peas, used primarily for soil improvement rather than harvest.

Looking for a specific variety?

Crimson Clover White Clover Red Clover Alfalfa Hairy Vetch Field Peas Cowpeas Winter Rye Sweet Clover Seradella

When should you plant Legume Cover Crops in your zone?

Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.

Get my Legume Cover Crops timeline →

Example Legume Cover Crops timeline · Pittsburgh, PA (Zone 6b)

Plant Legume Cover Crops
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Legume Cover Crops
Around Jun 1

≈ 45 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Legume Cover Crops dates for your own zip code.

Growing Conditions

☀️

Sun: Full sun, 6-8 hours daily; some species tolerate partial shade

💧

Water: Moderate moisture; most legume cover crops need 1-1.5 inches of water weekly. Establish plants are drought-tolerant; young seedlings need consistent moisture until established.

📏

Spacing: 4-6 inches for small-seeded legumes like clover; 6-12 inches for larger-seeded types like vetch or field peas inches

📅

Days to maturity: 45-120 days depending on species and climate; typically 60-90 days for full growth before incorporation

🌱

Planting depth: 0.25-0.75 inches depending on seed size; smaller seeds shallower, larger seeds deeper

Soil

Type: Well-draining loamy soil, adaptable to various soil types

pH: 6.0-7.5

Amendments:

Inoculant containing rhizobia bacteria (essential for nitrogen fixation) Lime if soil is acidic below pH 6.0 Organic matter for depleted soils

Growing Zones

Find your zone →

Most legume cover crops thrive in zones 3-9, with some species suitable for colder or warmer regions

1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b

Get my Legume Cover Crops timeline →

Growth Stages

Germination

7-14 days

Seeds sprout and first true leaves emerge. Seedlings are tender and vulnerable to competitive weeds.

Keep soil consistently moist but not waterlogged. Protect from strong winds and heavy foot traffic. Ensure good soil contact for inoculant effectiveness.

Vegetative Growth

3-6 weeks

Rapid leaf and stem development. Plants establish root systems and nodules begin forming. Foliage is lush green.

Monitor for weeds and pests. Light nitrogen supplementation only if plants show severe yellowing. Ensure inoculant is active by checking for nodules on roots.

Nodulation

4-8 weeks into growth

Nitrogen-fixing nodules develop on roots (visible when pulling a plant). This is critical for nitrogen accumulation.

Avoid excessive disturbance of roots. Proper inoculation is essential. Adequate phosphorus and potassium support nodule formation.

Flowering & Maturation

4-6 weeks

Flowers appear (species-dependent: purple, white, pink, or yellow). Seeds develop in pods. Biomass peaks.

Do not add synthetic nitrogen as it inhibits nodulation. Maximum nitrogen accumulation occurs at or just before full flower. Plan termination timing based on goals.

Termination & Incorporation

1-2 weeks for killing; 2-4 weeks for decomposition

Cover crop is killed via mowing, tilling, or frost and worked into soil to decompose and release nitrogen.

Terminate at peak biomass (full flower to early pod stage) for maximum nitrogen. Chop or mow before tilling. Allow 2-4 weeks decomposition before planting succeeding crop.

Companion Planting

Plan your garden →

Plant with:

Grasses (in mixed cover crop blends for better erosion control) Cereals like rye (in rotation as complementary cover crop) Brassicas (following legume cover crop in rotation)

Avoid planting near:

Heavy nitrogen feeders (only if goal is immediate cash crop; better to wait for soil integration) Legume diseases (avoid planting same legume species repeatedly in same field)

Common Pests

Usually not economically important on cover crops. Remove by strong water spray or tolerate. Predatory insects manage populations naturally.
Rarely serious. Scout plants; hand-pick if populations high. Rotate legume species.
Typically not a major issue. Monitor during hot, dry weather. Tolerate minor damage.
Remove debris that harbors slugs. Copper tape or diatomaceous earth around young seedlings if severe.

Uses

🌿

Nitrogen Fixation

Soil improvement

Legumes fix atmospheric nitrogen through symbiotic relationships with rhizobia bacteria, adding 50-300 lbs/acre of usable nitrogen to soil depending on species and conditions. This reduces synthetic fertilizer needs for subsequent crops. [source]

🏠

Erosion Control & Soil Structure

Household

Dense root systems prevent soil erosion, improve water infiltration, and build soil organic matter. This enhances soil structure and reduces compaction over time. [source]

🦋

Pollinator & Beneficial Insect Support

Wildlife

Flowering legume cover crops provide abundant nectar and pollen for bees, butterflies, and other beneficial insects, supporting pollinator populations and natural pest control. [source]

🍳

Livestock & Animal Forage

Culinary

Many legume cover crops (clover, alfalfa, vetch) are nutritious animal feed with high protein content. Can be grazed or harvested as hay before soil incorporation. [source]

💊

Phytoremediation

Medicinal

Some legumes accumulate heavy metals and can help clean contaminated soil. Certain species also suppress soil-borne pathogens through allelopathic compounds. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Cover crops are typically NOT harvested for yield. Instead, terminate at peak biomass—usually at full flower to early pod stage (8-12 weeks after planting). Mow or chop 2-3 weeks before planting the next crop to allow decomposition. For nitrogen accumulation, delay termination slightly; for fresh seed production of certain species, allow maturation. Winter-kill legumes naturally die with hard frost and can be incorporated in spring.

Fun Facts

🌱 A well-established legume cover crop can fix 100-300 pounds of nitrogen per acre per year—equivalent to several hundred dollars worth of synthetic fertilizer—making it one of the most cost-effective soil amendments in agriculture.
🌱 The nitrogen-fixing ability of legumes has been known and used for over 2,000 years; Roman farmers rotated fields with legumes to maintain fertility without understanding the bacterial mechanism (discovered in the 1800s).
🌱 Different legume species fix nitrogen at different rates and times; a diverse legume blend outperforms monocultures and spreads pest/disease risk across multiple plant species.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Cover Crop Full Sun Partial Shade pH True Leaves

Shop Legume Cover Crops plants and related plants at Plant Addicts →

Join 30,000 gardeners planning their gardens with LizPlants.

Get your personalized Legume Cover Crops planting timeline

Tell us your zip code and we'll calculate exactly when to start Legume Cover Crops seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.

Get my Legume Cover Crops timeline →