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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 spp. (Clover)

grass

Nitrogen-fixing legumes are perennial or annual plants that form symbiotic relationships with rhizobia bacteria in soil nodules, converting atmospheric nitrogen into plant-available forms. Alfalfa and clovers are commonly used as living mulches, cover crops, and ground covers to improve soil fertility and prevent erosion. These versatile plants also provide forage, wildlife habitat, and aesthetic ground coverage.

Looking for a specific variety?

Red Clover White Clover Crimson Clover Alfalfa 'Ranger' Alfalfa 'Saranac' 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)

    Around Jul 16

    ≈ 90 days after planting

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 to partial shade; 4-6 hours minimum daily for good establishment, though full sun (6-8 hours) is ideal for vigorous growth
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Water: Moderate to low water needs once established. Alfalfa is drought-tolerant with deep roots (up to 20 feet). Clovers need regular moisture during establishment (2-4 weeks) and during dry periods. Reduce watering once legumes are established.
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Spacing: Seed at 10-20 lbs/acre or 15-25 seeds per square foot for dense ground cover; thin or overseed to 6-12 inch spacing for individual plant visibility inches
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Days to maturity: Alfalfa: 90-180 days to first cutting; Clovers: 60-90 days to useful cover
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Planting depth: Shallow: 0.25-0.5 inches for fine seeds; press into soil contact after sowing

Soil

Type: Well-draining loamy to clay-loam soil with good structure
pH: 6.0-7.5
Amendments:
Lime to raise pH if below 6.0 (alfalfa prefers 6.5+) Phosphorus and potassium for establishment Organic matter/compost to improve soil structure Inoculant containing appropriate Rhizobium strain if legumes haven't been grown in soil recently

Growing Zones

Find your zone →

Alfalfa thrives in zones 3-9; clovers (especially red and white clover) are hardy in zones 2-8, with variations by species

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

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Growth Stages

1

Germination & Seedling

1-3 weeks

Fine cotyledons emerge, first true leaves unfold. Roots develop nodules with rhizobia bacteria beginning to form.

Keep soil consistently moist (not waterlogged). Avoid heavy foot traffic. Provide dappled sun to seedlings if possible. Begin nitrogen fixation partnership with soil microbes.

2

Establishment & Vegetative Growth

4-8 weeks

Plant develops deeper root system with nodules actively fixing nitrogen. Foliage becomes denser, stems strengthen, multiple shoots emerge.

Continue moderate watering during dry spells. Do not fertilize with nitrogen (inhibits nodulation). Mow once to 3-4 inches to encourage branching and density. Monitor for weeds.

3

Mature Ground Cover

Ongoing (perennial/semi-perennial)

Plant forms dense carpet or thick stand, typically 12-24 inches tall depending on variety and mowing schedule. Nitrogen fixation is well-established.

Maintain with occasional mowing (2-3 times per season) to 2-3 inches to keep dense and prevent woody growth. No fertilizer needed; nitrogen-fixation supplies nutrients. Suppress competing weeds by density.

4

Flowering & Nodule Peak Activity

4-8 weeks (spring and/or summer)

Small purple, pink, white, or yellow flowers appear depending on species. Nitrogen fixation peaks; nodules are largest and most active.

Allow flowers to bloom to support pollinators and beneficial insects. Delay mowing until after flower drop to maximize nitrogen fixation. Late summer flowering indicates vigor.

5

Decline & Winter Dormancy

8-20 weeks (varies by zone and winter severity)

Foliage fades and dies back in fall/winter. Perennial varieties remain dormant underground; roots and nodules persist.

Do not mow in late fall to allow regrowth protection. Spring will bring new shoots from crown. In warm zones, some clovers may remain green year-round.

Companion Planting

Plan your garden →

Plant with:

Grasses (perennial ryegrass, timothy, tall fescue) for mixed pastures Chicory and plantain for diverse pasture mixes Annual rye cover crops (rotational) Wildflowers for pollinator support Non-legume cover crops like oats or barley in crop rotations

Avoid planting near:

Heavy nitrogen fertilizer applications (inhibits nodulation and nitrogen fixation) Legume monocultures for more than 2-3 years (pest and disease buildup) Herbicides containing imazapyr or other persistent residues Photosynthetic efficiency competitors in very shaded areas (out-compete legumes)

Common Pests

  • Early spring mowing before larval hatch; biological control with parasitoid wasps; avoid excessive nitrogen fertilizer that increases susceptibility

  • Timely mowing and clipping removal; crop rotation; early detection and removal of infested plants

  • Natural predators (ladybugs, lacewings); strong water spray; insecticidal soap if severe; avoid excess nitrogen

  • Maintain dense stand to reduce feeding sites; early mowing; parasitic flies; handpick if isolated

  • Encourage natural predators; reflective mulches; neem oil if needed; balanced fertility

  • and (Phytophthora, Rhizoctonia)

    Ensure excellent drainage; avoid waterlogging; use disease-resistant varieties; rotate crops; remove severely diseased plants

Uses

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Nitrogen fixation and soil fertility improvement

Household

Legume-Rhizobium symbiosis fixes atmospheric nitrogen into available forms, reducing or eliminating synthetic fertilizer needs. When plants die back or are incorporated into soil, nitrogen becomes available to subsequent crops and surrounding plants. [source]

🍳

Nutritious livestock forage

Culinary

Alfalfa and clovers are high-protein forages used for hay, silage, and pasture, providing essential amino acids and vitamins for cattle, sheep, goats, and horses. Dried clover and alfalfa are valuable feed supplements. [source]

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Pollinator and beneficial insect habitat

Wildlife

Flowers attract bees, butterflies, and other pollinators. The plant provides food and shelter for beneficial predatory insects, birds, and small mammals. [source]

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Erosion control and soil conservation

Household

Dense root systems and above-ground coverage stabilize soil, reduce runoff, and prevent gully formation on slopes. Also improves soil structure and water infiltration over time. [source]

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Herbal and nutritional supplements

Medicinal

Alfalfa is rich in vitamins K, U, and minerals; used in herbal medicine for arthritis, cholesterol, and digestive health. Clover flowers contain isoflavones and are used in teas for bone health. [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 nitrogen fixation benefit: allow plants to establish for 4-6 weeks, then maintain with 2-3 mowings per season, cutting to 2-3 inches. For forage: cut at early bloom (10% flowering) for best nutrition and regrowth. For seed production: allow full flowering and seed set, harvest when pods dry (late summer). For soil incorporation (green manure): plow under at peak vegetative growth or early bloom. Clip/mulch mowed material to return nitrogen to soil, or remove for compost.

Fun Facts

  • 🌱 A single alfalfa plant can have a root system that extends 15-30 feet deep, allowing it to access water and nutrients unavailable to shallow-rooted plants—this is why alfalfa is called the 'queen of forages.'
  • 🌱 Legume-Rhizobium symbiosis can fix 100-300 lbs of nitrogen per acre per year without any synthetic fertilizer, making nitrogen-fixing legumes one of the most sustainable agricultural practices.
  • 🌱 Clover lawns were once the norm in home gardens before synthetic nitrogen fertilizers became widespread; the recent 'clover lawn' movement is a return to low-input, pollinator-friendly landscaping.

Gardening Terms

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

Annual Compost Cover Crop Crown Full Sun Green Manure Mulch Partial Shade Perennial pH True Leaves
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