Alfalfa is a cover crop — grown to build and protect the soil rather than for a harvest of its own. It's hardy across USDA zones 2 through 10 and shrugs off dry spells. Its spring flowers are a real draw for honeybees and native bees. A nitrogen-fixer, it draws nitrogen from the air and feeds it back to the soil — turn it under or leave the roots in place, and the next planting inherits a richer bed.
Zones
2-10
pH Range
4.3-8.7
Sun
Full Sun
Days to Maturity
65
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What Alfalfa is
Alfalfa grows as an annual or perennial and reaches around three feet at maturity. It blooms purple in spring.
How to grow Alfalfa
Alfalfa grows in USDA zones 2 through 10. Alfalfa does best in full sun — at least 6 hours of direct sun a day — and soil from pH 4.3 to 8.7, on well-drained ground. It needs around 2,500 growing degree days to mature and a growing season of at least 100 frost-free days, which is why climate matters as much as soil.
USDA Zones
2-10
USDA PHZM 2023
Soil pH
4.3 - 8.7
USDA PLANTS Database
Sun
Full Sun
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Frost Tolerance
41°F
The lowest temperature it shrugs off — below this, expect damage without cover.
Growable Ground plant catalog
Days to Maturity
65 days
Alfalfa; perennial nitrogen-fixing cover; deep tap root; multi-year stand.
SARE; USDA-NRCS
GDD Required
2500+
Growing degree-days of accumulated warmth it needs to mature — humid summers reach this faster than cool coastal ones.
Growable Ground plant catalog
Mature Height
3 ft
Growable Ground plant catalog
Frost-Free Days
100+
The frost-free stretch it needs start to finish — short-season areas may need an indoor head start.
Growable Ground plant catalog
Start the season right
Plant alfalfa in full sun with at least 6 hours of direct sun, once the soil has warmed and frost risk has passed.
Match the soil
Alfalfa prefers pH 4.3 to 8.7 (FAO ECOCROP). A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band. It fixes its own nitrogen, so skip the high-nitrogen feed and instead dust the seed with a matching rhizobium inoculant at sowing.
Water steadily
Keep the root zone evenly moist through establishment. A 2–3 inch mulch layer holds moisture without waterlogging.
Turn it in before it seeds
Cut alfalfa down or turn it into the soil before it sets seed, while the growth is still green — that's when it returns the most to the ground.
Good to know
Good news for pet owners — alfalfa isn't known to be toxic to dogs or cats. (Source: ASPCA.)
Alfalfa is a standout pollinator plant — high value to bees and other pollinators. (Source: Xerces Society.)
Where Alfalfa thrives
On hardiness alone, alfalfa grows across most of the country — its range (USDA zones 2 through 10) is unusually wide. Zone is only the starting point, though: the soil pH, drainage, and frost dates on your specific land decide how well it actually does.
Zones 2–10·Where Alfalfa growsOpen map →
Continental US shown — Alaska and US Pacific territories sit outside the federal map's polygon dataset.
On USDA hardiness-zone overlap, Alfalfa can grow in these states:
See if Alfalfa will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether alfalfa actually takes — we score it against the real conditions at your address.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Frequently Asked Questions
Can I grow Alfalfa in my zone?
Alfalfa grows in USDA hardiness zones 2 through 10 (USDA PHZM 2023). Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
When should you plant Alfalfa?
Most growers plant alfalfa after the last spring frost, once the soil has warmed, leaving enough of the season for its 100-day frost-free need. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
How much sun does Alfalfa need?
Alfalfa needs full sun — a spot that catches at least 6 hours of direct summer sun a day. In more shade it still grows, but usually gives a smaller, later crop. The catch is that a yard rarely gets even light everywhere — a fence, the house, or one tall tree can quietly take those hours. A Growable Ground report reads the real sun-hours across your land, canopy and buildings included, so you can pick the brightest bed before you plant.
What soil does Alfalfa need?
Alfalfa prefers soil pH 4.3 to 8.7, on well-drained ground (FAO ECOCROP). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Alfalfa attract pollinators?
Yes — alfalfa's flowers are a strong nectar and pollen source for honeybees and native bees. (Source: Xerces Society.)
Is Alfalfa safe for pets?
Alfalfa is not known to be toxic to dogs or cats based on available data. Always supervise pets around new plantings. (Source: ASPCA.)