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How to Grow Nitrogen-fixing Legumes (Alfalfa & Clover)

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Nitrogen-fixing Legumes (Alfalfa & Clover)

Medicago sativa (Alfalfa) / Trifolium species (Clover)

grass

Nitrogen-fixing legumes are perennial or annual plants that form symbiotic relationships with Rhizobium bacteria in their root nodules, converting atmospheric nitrogen into plant-available forms. Alfalfa and various clover species are widely used as ground cover, cover crops, and soil amendments in agricultural and garden settings. These plants improve soil fertility naturally while providing erosion control, wildlife forage, and aesthetic ground cover.

Looking for a specific variety?

Lucerne (Medicago sativa subsp. sativa) - alfalfa Grimm Alfalfa Red Clover White Clover Crimson Clover Alsike Clover

When should you plant Nitrogen-fixing Legumes (Alfalfa & Clover) in your zone?

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Example Nitrogen-fixing Legumes (Alfalfa & Clover) timeline · Pittsburgh, PA (Zone 6b)

  1. Plant Nitrogen-fixing Legumes (Alfalfa & Clover)

    Around Apr 17

    Near Pittsburgh's average last spring frost.

  2. Tend & protect

    Late spring–summer

    Watering, feeding, and pest-watch reminders.

  3. Harvest Nitrogen-fixing Legumes (Alfalfa & Clover)

    Late summer into fall

    Before the first fall frost (≈ Nov 8)

Sample dates for Pittsburgh, PA. Sign up to get exact Nitrogen-fixing Legumes (Alfalfa & Clover) dates for your own zip code.

Growing Conditions

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Sun: Full sun, 6-8 hours daily minimum; alfalfa requires 6+ hours; most clovers tolerate partial shade (4-6 hours)
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Water: Moderate; alfalfa is drought-tolerant once established with deep taproot; clovers need consistent moisture during establishment. Water deeply 1-2 times weekly during first 4-6 weeks, then reduce frequency. Avoid waterlogging.
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Spacing: 6-12 inches apart for transplants or broadcast seed at 15-20 lbs/acre (approximately 0.35-0.5 lbs per 1000 sq ft for garden use) inches
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Days to maturity: 45-60 days to initial usable cover; 6-12 months for full establishment and nitrogen fixation
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Planting depth: 1/4 to 1/2 inch deep; very shallow planting; broadcast seed then rake in lightly or use a cultipacker

Soil

Type: Well-draining loamy to clay loam soil; alfalfa prefers slightly alkaline soils
pH: 6.0-7.5 (alfalfa prefers 6.5-7.5; clovers more flexible at 6.0-7.0)
Amendments:
Lime (if pH is below 6.0 for alfalfa) Compost or aged manure for initial soil improvement Inoculant containing Rhizobium bacteria (critical for nitrogen fixation) Avoid excessive nitrogen fertilizer; it inhibits nodulation

Growing Zones

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Alfalfa thrives in zones 4-9; most clovers grow in zones 3-9 depending on variety

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

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Growth Stages

1

Germination & Seedling

2-3 weeks

Tiny cotyledons emerge 7-14 days after planting. First true leaves develop with characteristic clover triple-leaflets or alfalfa compound leaves.

Keep soil consistently moist but not waterlogged. Protect seedlings from strong wind and full sun stress initially. Ensure good inoculant contact with seed.

2

Establishment

4-8 weeks

Root system develops, including taproot in alfalfa. Plants fill out laterally and develop secondary growth. Nodulation begins as Rhizobium bacteria colonize roots.

Maintain even moisture. Mow occasionally at 2-3 inches if weeds compete heavily. Avoid nutrient fertilizer; let nitrogen fixation commence. Monitor for pest activity.

3

Vegetative Growth

8-12 weeks

Rapid leafy growth; plants thicken and spread. Nitrogen fixation increases, enriching soil. Plants develop robust root systems with visible nodules.

Mow or graze as desired (typically at 6-8 inches before flowers appear for forage quality). First cutting can occur 8-10 weeks after planting if growth is vigorous.

4

Flowering

4-6 weeks

Small purple, white, pink, or yellow flowers appear depending on species. Alfalfa produces purple spikes; clovers form rounded flower heads.

Allow some flowering for pollinator benefit and seed set. If using as forage, cut just before flowering for optimal nutrition. Do not cut below 2-3 inches.

5

Maturation & Sustainability

Ongoing (perennial) or seasonal (annual)

Plant enters dormancy in winter (perennial) or completes life cycle (annual). Soil nitrogen content increases measurably from fixed nitrogen. Plant re-sprouts vigorously in spring.

Little active care needed. Allow winter dormancy; do not heavily disturb roots. Remove thatch if excessive. Plan for renovation or reseeding every 3-5 years if productivity declines.

Companion Planting

Plan your garden →

Plant with:

Grass species (timothy, orchard grass, perennial rye) for mixed pasture Chicory (enhances forage quality) Plantain (encourages root development) Comfrey (mineral accumulation) Sainfoin (complementary legume)

Avoid planting near:

Heavy-feeding crops requiring high nitrogen initially (the legume gradually provides it) Medicago-damaging pathogens (verticillium wilt hosts nearby) Root-competing deep perennials until legume is well-established

Common Pests

  • Timely mowing/cutting at early bloom stage; predatory wasps; pyrethrin spray for severe infestations

  • Reflective mulch; early cutting; insecticidal soap for severe damage

  • Rotation; early cutting to remove eggs; beneficial nematodes in soil

  • Strong water spray; insecticidal soap; encourage ladybugs and parasitic wasps

  • and

    Copper barriers; beer traps; encourage ground beetles and predatory insects

  • Adequate spacing for air circulation; avoid overhead watering; remove affected leaves; resistant varieties

Uses

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Animal fodder & forage

Culinary

Alfalfa and clover are high-quality forage crops for livestock (cattle, sheep, goats, horses), providing protein and essential nutrients. Dried alfalfa hay is a standard feed for herbivores worldwide. [source]

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Traditional herbal remedy

Medicinal

Alfalfa leaf tea is used in herbal medicine to support bone health, digestion, and vitamin K intake. Clover has been used traditionally for respiratory health and hormonal balance. [source]

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Soil fertility & nitrogen fixation

Household

These legumes fix atmospheric nitrogen through symbiotic relationships with Rhizobium bacteria, naturally enriching soil and reducing the need for synthetic fertilizers. Incorporating 1-2 years of legume cover increases soil nitrogen by 100-300 lbs/acre. [source]

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Pollinator & wildlife habitat

Wildlife

Flowering legumes attract bees, butterflies, and beneficial insects. Ground cover provides habitat for small mammals and ground-nesting birds. [source]

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Erosion control & soil stabilization

Household

Dense legume cover stabilizes soil, reduces erosion on slopes, and improves soil structure through root penetration and organic matter accumulation. Particularly valuable on marginal or degraded land. [source]

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

Harvest Tips

For forage: Cut at early bloom stage (10-14% bloom) for peak nutrition; typically 3-4 cuttings per season in temperate zones. For soil amendment: Allow first year growth without heavy cutting, then use biomass by mowing and leaving cut material on field, or incorporate into soil by tilling in fall/early spring. For seed: Allow flowers to mature and dry; collect when pods turn brown. Do not cut below 2-3 inches to protect crown and future growth.

Fun Facts

  • 🌱 Alfalfa is called 'the king of forage crops' and can live 10+ years, with a taproot reaching 15+ feet deep to access water and nutrients unavailable to shallow-rooted plants.
  • 🌱 A well-nodulated legume crop fixes 100-300 pounds of nitrogen per acre annually without any fertilizer input—equivalent to several commercial nitrogen applications.
  • 🌱 Clover used to be intentionally included in lawn seed mixes throughout the 20th century until chemical herbicides made selective grass-only lawns fashionable; it's now experiencing a comeback as gardeners value its nitrogen-fixing ability and pollinator support.

Gardening Terms

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

Amendment Annual Cover Crop Crown Full Sun Partial Shade Perennial pH True Leaves
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