Key Facts
- Perennial forage legume grown for hay, pasture, and cover cropping
- Deep taproot that improves drought tolerance and soil structure
- Fixes atmospheric nitrogen via symbiosis with rhizobia
- Produces purple to blue pea shaped flowers in clusters
- Prefers full sun and well drained soils
- Requires inoculation with compatible rhizobia for best nodulation from seed
- Can cause bloat in grazing ruminant livestock when grazed lush
- Long lived in cool temperate climates but can be short lived in hot humid regions
Alfalfa is a deep rooted perennial legume grown for hay pasture and cover crops that fixes atmospheric nitrogen and improves soil structure. It produces purple to blue pea shaped flowers and favors full sun with well drained soils but may be shorter lived in hot humid regions.
Identification
Plants reach about 1 to 3 feet tall with a deep taproot that boosts drought tolerance and anchors crowns. Leaves are compound and flowers appear in clusters of purple to blue pea shaped blooms from late spring into summer. Individual crowns or clumps typically occupy roughly 1 to 2 feet once established.
Where to grow Alfalfa
Alfalfa is used for hay pasture and cover cropping and adds nitrogen through symbiosis with rhizobia. It performs best in full sun and well drained loam to sandy loam with an ideal soil pH near 6.5 to 7.5. Hardiness generally falls between USDA zones 3 and 9 depending on cultivar and management.
Planting and establishment
Alfalfa is established primarily by seed and seed should be inoculated with compatible rhizobia for best nodulation. Established stands regenerate from crowns and from self seed. Sowing timing and seeding density vary by region and management because persistence and reseeding depend on local climate and cultivar choice.
Water and soil
Alfalfa prefers well drained soils and is intolerant of poor drainage and compaction which reduce nodulation and stand longevity. A deep taproot gives good drought tolerance once established. Avoid waterlogged conditions because poor drainage harms plants and reduces nitrogen fixation.
After flowering and management
Cutting schedule affects flowering and regrowth so manage stands for the intended use either hay or cover crop. Allowing some flowering encourages reseeding in stands intended to naturalize while regular cutting maximizes forage yield. Choose cultivars and timing suited to your climate to improve stand life.
Spread and control
Alfalfa spreads slowly by crown development and by new seedlings from seed in dense stands. Individual plants typically occupy about 1 to 2 feet. It is not widely listed as invasive but can naturalize in favorable conditions so monitor stands and manage seed set if you want to limit spread.
Frequently asked questions
- How fast does Alfalfa grow?
- Under favorable conditions plants reach their typical height of 1 to 3 feet within the growing season. Growth rate depends on climate soil fertility and cutting or grazing management.
- Does alfalfa fix nitrogen?
- Yes alfalfa forms a symbiosis with rhizobia to fix atmospheric nitrogen. Seed inoculation with a compatible rhizobial strain helps ensure good nodulation especially where alfalfa has not been grown recently.
- Is alfalfa safe for livestock and pets?
- Alfalfa is valuable forage but lush grazing can cause bloat in ruminant livestock. Pet toxicity is not clearly flagged as high risk but verify with local poison control or ASPCA resources before offering alfalfa to pets.
- How long does an alfalfa stand last?
- Stand longevity varies by cultivar climate and management. It tends to be long lived in cool temperate regions and may be shorter lived or require reseeding in warmer humid zones.
- Do I need to inoculate alfalfa seed?
- Yes inoculation with a compatible rhizobial inoculant is recommended for best nodulation from seed particularly where Medicago sativa has not been previously established.
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