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How to Grow Cover Crops (Clover & Alfalfa)

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Cover Crops (Clover & Alfalfa)

Trifolium spp. (Clover), Medicago sativa (Alfalfa)

grass

Cover crops are legume plants grown primarily to improve soil health rather than for harvest. Clover and alfalfa are nitrogen-fixing legumes that form symbiotic relationships with soil bacteria, enriching soil with nitrogen while preventing erosion and suppressing weeds. They are essential components of sustainable crop rotation systems.

Looking for a specific variety?

Red Clover White Clover Ladino Clover Crimson Clover Alfalfa Sweet Clover

When should you plant Cover Crops (Clover & Alfalfa) in your zone?

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Example Cover Crops (Clover & Alfalfa) timeline · Pittsburgh, PA (Zone 6b)

  1. Plant Cover Crops (Clover & Alfalfa)

    Around Apr 17

    Near Pittsburgh's average last spring frost.

  2. Tend & protect

    Late spring–summer

    Watering, feeding, and pest-watch reminders.

  3. Harvest Cover Crops (Clover & Alfalfa)

    Late summer into fall

    Before the first fall frost (≈ Nov 8)

Sample dates for Pittsburgh, PA. Sign up to get exact Cover Crops (Clover & Alfalfa) dates for your own zip code.

Growing Conditions

☀️
Sun: Full sun, 6-8 hours daily; both tolerate partial shade but prefer full sun for vigorous growth
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Water: Moderate, consistent moisture during establishment (1-2 inches per week); once established, both are drought-tolerant and require minimal supplemental watering. Avoid waterlogging, which reduces nitrogen fixation efficiency and promotes disease.
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Spacing: Broadcast seed at 15-20 lbs/acre for clover; 20-30 lbs/acre for alfalfa. Thin seedlings to 4-6 inches apart if direct seeding small areas. inches
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Days to maturity: Not harvested for maturity; typically grown for 1-3 years in rotation before incorporation or grazing
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Planting depth: Surface to 1/4 inch deep; press seed firmly into soil for good contact

Soil

Type: Well-draining loamy to clayey soil with good organic matter content
pH: 6.0-7.5 (Alfalfa prefers 6.5-7.5; Clover tolerates 5.5-7.0)
Amendments:
Compost or aged manure for organic matter Rock phosphate for phosphorus Potassium sources if deficient Lime if pH is below 6.0 Inoculant with Rhizobium bacteria for optimal nitrogen fixation

Growing Zones

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Clover thrives in zones 2-9; Alfalfa performs best in zones 4-9, with winter hardiness varying by variety

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

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Growth Stages

1

Germination & Establishment

2-4 weeks

Seeds germinate in 5-10 days with adequate moisture. Seedlings emerge with cotyledons and develop first true leaves within 2-3 weeks.

Keep soil consistently moist but not waterlogged. Avoid heavy traffic on young seedlings. Apply inoculant at planting if soil lacks Rhizobium bacteria. Control competing weeds manually or with mechanical cultivation.

2

Vegetative Growth

3-8 weeks for first cutting; may cycle multiple times per season

Rapid leaf and root development; plants establish deep root systems (clover 3-5 feet; alfalfa 6-10+ feet). Multiple stems emerge from the crown.

Minimal inputs required. First cutting or grazing can begin when plants reach 6-8 inches tall. Do not over-graze—leave 2-3 inches of stubble to support regrowth. Nitrogen fixation is most active during this stage.

3

Flowering

2-4 weeks

Small clustered flowers appear (white, pink, or purple depending on species). Plant reaches peak biomass and nitrogen fixation.

If harvesting for hay, cut before flowers fully open to maximize nutrient content and encourage regrowth. Timing varies: early spring through late fall depending on climate and planting date. Leave roots in soil to release fixed nitrogen.

4

Post-Harvest/Senescence

2-12 weeks depending on season and latitude

After cutting or grazing, plants regrow from crown. In colder zones, plants harden off as days shorten and temperatures drop.

Each cutting removes biomass but stimulates deeper rooting and nitrogen accumulation. Alfalfa tolerates more cuttings (3-4 per season) than clover. Allow fall growth to accumulate before incorporating or overwintering.

5

Incorporation/Rotation Transition

Termination occurs once; decomposition takes 4-12 weeks

At end of cover crop cycle (1-3 years), plants are tilled or left to decompose in place, returning fixed nitrogen and organic matter to soil.

Time incorporation 2-4 weeks before planting main crop to allow residue to break down. In no-till systems, terminate with herbicide or mechanical means. Nitrogen becomes available gradually over 4-8 weeks as organic matter decomposes.

Companion Planting

Plan your garden →

Plant with:

Grasses (in diverse pasture mixes) Chicory (in pasture blends) Birdsfoot trefoil Sainfoin Other legume cover crops (in rotation, not simultaneously)

Avoid planting near:

Nitrogen-demanding vegetables in same season (plant cover crop one season, main crop the next) Other deep-rooting crops simultaneously (competition for soil resources) Heavy clay soils with poor drainage (alfalfa particularly susceptible to root rot)

Common Pests

  • Early cutting to remove eggs and larvae; rotate cutting schedules; natural predators like tachinid flies; insecticides if severe

  • Timely harvesting before peak larval feeding; allows regrowth; rarely requires intervention in cover crop context

  • Maintain adequate moisture; encourage predatory insects; insecticides only in severe outbreaks

  • Strong water spray; biological predators (ladybugs, lacewings); rarely problematic in established cover crops

  • Ensure good air circulation; avoid overhead watering; remove infected portions; fungicides rarely needed

  • Select disease-tolerant varieties; avoid overhead irrigation; remove infected plant material; may resolve after termination

Uses

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Soil Nitrogen Enrichment

Household

Legume cover crops fix atmospheric nitrogen through symbiotic relationships with Rhizobium bacteria, eliminating the need for synthetic nitrogen fertilizers. A mature alfalfa stand can fix 100-200 lbs of nitrogen per acre annually, significantly reducing input costs and environmental impact. [source]

🏠

Erosion Control & Soil Structure

Household

Deep root systems stabilize soil, prevent erosion, and improve soil aggregation and water infiltration. The extensive root networks create macropores that enhance drainage and aeration, especially beneficial after heavy cultivation or compaction. [source]

🏠

Weed Suppression & Organic Matter

Household

Dense cover crop growth outcompetes weeds, reducing seed bank and herbicide need. Upon incorporation, the biomass adds organic matter, improving soil fertility, water retention, and microbial activity for years. [source]

🍳

Livestock Forage & Grazing

Culinary

Clover and alfalfa are nutritious forage crops that provide pasture for cattle, sheep, goats, and other livestock. They are high in protein and minerals, supporting animal health while allowing rotational grazing systems that rest other pastures. [source]

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Disease & Pest Cycle Breaking

Household

Rotating cover crops interrupts pest and disease life cycles for subsequent cash crops. The allelopathic properties of some clovers and the microbial activity stimulated by legumes can suppress soil-borne pathogens and reduce pest pressure naturally. [source]

Harvest Tips

Cover crops are not typically harvested for consumption but rather grazed, cut for hay/silage, or incorporated into soil. For maximum nitrogen fixation and biomass, allow growth to peak flowering stage. Cut when 6-8 inches tall for grazing to avoid plant stress and encourage regrowth. If harvesting for hay, cut in early morning after dew dries. For soil incorporation, terminate in late fall or early spring before main crop planting. In annual rotation, grow cover crop through fall/winter or early spring, terminate 2-4 weeks before planting main crop.

Fun Facts

  • 🌱 Alfalfa can reach depths of 20+ feet, tapping groundwater and deep soil nutrients unavailable to shallow-rooted crops. Some plants are over 50 years old, making alfalfa one of agriculture's longest-lived perennials.
  • 🌱 A single alfalfa or clover plant can fix enough nitrogen to supply multiple cash crop plants in subsequent seasons. The nitrogen remains in the soil as organic matter even after plant residue decomposes.
  • 🌱 Clover was called 'trefoil' in medieval times and was sacred to Celtic druids. Four-leaf clovers are natural genetic variants (recessive mutation) occurring in roughly 1 in 5,000 plants.

Gardening Terms

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

Annual Cover Crop Crown Full Sun Partial Shade Row Cover True Leaves
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