Yes — Strong Match
alfalfa (zones 2-10) covers every zone Colorado contains (3b-7b), so hardiness is not what limits it anywhere in the state.
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Zone Comparison
Alfalfa Needs
- USDA Zones: 2-10
- Frost-Free Days: 100+
- Sun: Full Sun
- Mature size: 3 ft tall
- Drought tolerance: High
Colorado Has
- USDA Zones: 3b-7b
- Last Hard Freeze (28°F): Apr 25 - May 19
- First Hard Freeze (28°F): Sep 29 - Oct 16
- Annual Rainfall: 7-20 inches
- Common Soils: Sandy loam, Clay loam, Alkaline caliche
Plant Zone Range (zones 2-10)
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Alfalfa in Colorado
The frost window
Across Colorado, the last spring hard freeze (28°F) clears between Apr 25 and May 19, and the first fall hard freeze lands between Sep 29 and Oct 16 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 133-day window you can count on — up to 174 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
When to start the seed
Alfalfa is direct-sown where it grows rather than started under cover, so there is no seed-tray head start to bank — Colorado's dates above are the whole calendar for it. That makes the last-freeze date the binding constraint, and a warmer pocket of your own yard is worth more to this crop than it is to a transplanted one.
Winter standing
Colorado runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for alfalfa, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether alfalfa is a permanent planting or a replant-every-spring crop for you turns on your own zone within Colorado; check its hardiness range against that before treating it as long-lived ground.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says alfalfa survives winter here. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Alfalfa wants 100+ frost-free days; a typical Colorado site sees ~155 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
Growing degree days
Alfalfa needs ~2500 GDD (base 50°F) to ripen. The state median runs ~2083 GDD (from PRISM 1991-2020 climate normals), so Colorado's typical season runs short on heat — pick a south-facing site and consider season extension.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Alfalfa tolerates a wide pH range (pH 4.3-8.7) — 4.4 units, acid ground through alkaline — so soil acidity is rarely what limits it in Colorado. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 6.5 and 7.5 — worth knowing before you decide whether a Colorado soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Colorado site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH and drainage requirements from USDA PLANTS Database. Colorado soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Alfalfa in Colorado — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: 2-10 (USDA PLANTS Database)
- State Zones: 3b-7b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 25 - May 19 to Sep 29 - Oct 16 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 65 days
What Else to Consider for Alfalfa in Colorado
Zone compatibility tells you about winter cold survival — but Colorado growers also need to think about:
Low annual rainfall (7-20 inches) means irrigation is essential nearly everywhere
High altitude UV and temperature swings stress plants
Very short growing season at elevation (60-90 frost-free days above 8,000 ft)
Alkaline soils (pH 7.5-8.5) limit acid-loving plants without amendment
What to actually do about these — and the constraints that apply to every Colorado grower, not just alfalfa — is covered on the Colorado growing guide.
Timing shifts within Colorado
Alfalfa needs about 100 days of frost-free season to complete its cycle. 60 of Colorado’s 64 counties give it that outright. The tightest that does is Summit County at 102 frost-free days — 2 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Colorado’s 64 counties the frost-free season runs from 85 days in Chaffee County to 209 days in Mesa County — a spread of 124 days, which is why a single statewide planting date misleads. The median Colorado county sees 155 frost-free days, leaving alfalfa about 55 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Alfalfa's 100-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in Colorado Fits Best
Even within Colorado's zones 3b-7b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for alfalfa (USDA PHZM 2023):
Pollinator + Wildlife Value
Alfalfa draws honeybees and native bees (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, alfalfa can only work that bloom inside Colorado's frost window — roughly 155 days, opening after the last 28°F freeze (Apr 25 - May 19) and closing at the first (Sep 29 - Oct 16), per NOAA Regional Climate Centers ACIS, 1991-2020.
Colorado Cooperative Extension
For Colorado-specific cultivar recommendations, planting calendars, and pest pressure for alfalfa, the canonical source is Colorado State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Alfalfa native to Colorado?
No — the USDA PLANTS Database lists Alfalfa as introduced rather than native in the Lower 48, so it is not part of Colorado's native flora. It grows here as a garden plant; pairing it with a few Colorado natives keeps local pollinators fed too.
Looking for plants that belong here? The Colorado growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Alfalfa in Colorado
When can I plant Alfalfa in Colorado?
Colorado's last spring hard freeze (28°F) clears between Apr 25 and May 19, and the first fall hard freeze lands between Sep 29 and Oct 16 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Alfalfa, so this page does not state whether it overwinters in Colorado and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Alfalfa grown in across Colorado?
Colorado spans USDA hardiness zones 3b-7b (USDA ARS PHZM 2023). Alfalfa carries a range of zones 2-10, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Colorado site have?
A typical Colorado site sees ~155 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Alfalfa needs 100+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Alfalfa native to Colorado?
No — the USDA PLANTS Database lists Alfalfa as introduced rather than native in the Lower 48, so it is not part of Colorado's native flora. It grows here as a garden plant; pairing it with a few Colorado natives keeps local pollinators fed too.
How should I amend the soil for Alfalfa in Colorado?
Alfalfa tolerates pH 4.3-8.7 and well (dry spells) drainage (FAO ECOCROP). That is a 4.4-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Colorado site — amend for drainage and organic matter first.
Will Alfalfa actually grow on my specific land in Colorado?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores alfalfa against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Colorado
State-level data is a sketch. Your Growable Ground report scores alfalfa against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Colorado alfalfa averages can't show:
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