Alamosa, Colorado, sits in USDA hardiness zone 4b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Crops well matched to these conditions include cabbage, cranberry, cilantro, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Alamosa, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Alamosa lot. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Alamosa — soil, climate, flood, and parcel records. How we handle your address.
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Alamosa — the short answer
Alamosa, Colorado: USDA zone 4b, about 126 days between hard freezes, across 5K acres of city.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 25
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~126
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 5K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 4b is Alamosa's average, not your lot's — a low corner or a tree line moves it. Against Alamosa's 126-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Alamosa
Each reading below is measured for Alamosa itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredAlamosa runs about 126 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredAlamosa sits in USDA hardiness zone 4b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Alamosa is in
Alamosa sits in the Arizona/New Mexico Plateau — EPA Level III, inside the wider North American Deserts. That is read at Alamosa's own centroid rather than borrowed from Alamosa County.
What Grows in Alamosa
Every plant below cleared Alamosa's own zone 4b and its 126-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Alamosa?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Apr 24; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 22 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 25 — long-season crops need about 90 days of runway, quick greens only 30. Even here the calendar’s edges hold value: thirty-day greens late in the window, then garlic and a rested bed for spring.
What's on the federal record near Alamosa
Closest first, within ~10 miles of Alamosa. Listing isn't leaking, and distance isn't exposure.
- ADAMS STATE FAMILY HOUSINGBrownfields · 1600 ft
- Adams State CollegeUnderground Storage Tanks · 1800 ft
- Safeway Fuel Center #1681Underground Storage Tanks · 1800 ft
- San Luis Valley Regional Medical CenterUnderground Storage Tanks · 1800 ft
- Alamosa RcagUnderground Storage Tanks · 1900 ft
- Cumbres Pass Parking AreaUnderground Storage Tanks · 2100 ft
- Alta Convenience #5601Underground Storage Tanks · 2100 ft
- LUTHERAN HOSPITAL ASSOCIATION DBA SAN LUIS VALLEY HEALTHBrownfields · 2100 ft
- Old Phillips StaUnderground Storage Tanks · 2300 ft
- Winco Standard - MainUnderground Storage Tanks · 2300 ft
- Winco Food StoreUnderground Storage Tanks · 2300 ft
- SAFEWAY STORE #1681Brownfields · 2300 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Alamosa's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Alamosa.
Total Sites
148
within ~10 miles of Alamosa
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Alamosa
Severity Distribution
within ~10 miles of Alamosa
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Alamosa, Nitrate runs higher than the national average — 66 sites within ~10 miles of Alamosa. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Alamosa
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Alamosa average
Your land is one point inside Alamosa
Everything above resolves to Alamosa as a whole — one PHZM band and one 28°F frost record, read across 5K acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at city scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better local average.
Your Lot vs the Alamosa Average
Alamosa Average
- ●USDA Zones 4b, averaged across Alamosa
- ●One soil character for all of Alamosa
- ●Frost dates read at Alamosa's scale: May 22 to Sep 25
YOUR Parcel
- ✓Your exact zone, not Alamosa's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Alamosa
Pull a site-specific report for your exact address in Alamosa, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Alamosa averages can't show:
We read public map data around Alamosa — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Alamosa average
How we know this about Alamosa
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Alamosa’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Alamosa
When does frost risk typically end in Alamosa?
The last hard freeze (28°F) in Alamosa typically lands around May 22, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Jun 12.
When is the first frost in Alamosa?
The first hard freeze (28°F) in Alamosa typically arrives around Sep 25, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 11, so the watching starts about Aug 26 — about 126 days after the spring freeze cleared.
How long is the growing season in Alamosa?
Measured between 28°F hard freezes, Alamosa sees about 126 frost-free days — roughly May 22 through Sep 25, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 12 to Sep 11, about 91 days.
Is the soil safe to grow vegetables in Alamosa?
The federal record around Alamosa is a meaningful one — 148 documented sites, mostly Nitrate entries (66), the nearest Brownfields record about 0.3 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do gardeners stretch the season in Alamosa?
With about 126 frost-free days between hard freezes, Alamosa rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 154 to 182 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 22 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Alamosa's scale — its 4b band and its 126-day season. Your yard writes its own version of Alamosa's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Alamosa’s own scale
6 of the readings below were taken at Alamosa's own scale — its own ~126-day season between 28°F freezes, the 5,098 acres it covers and 148 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Alamosa's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Alamosa's own 28°F hard-freeze dates, about May 22 and Sep 25 and the ~126-day span between themNOAA 1991–2020 Climate Normals
- 148 documented contamination sites on the federal record near Alamosa, the closest Brownfields record about 0.3 miles out from the town centreFederal environmental registers
- Alamosa's boundary and the 5,098 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~126-day seasonGrowable Ground crop-matching engine
- The ecoregion at Alamosa's own centroid, the Arizona/New Mexico PlateauUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Alamosa's 5,098 acres read through its county's SSURGO summaryfrom Alamosa County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Alamosa County
- The growing challenges every Colorado grower plans around — written at state scale, so they stay on the state guidefrom Colorado
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Alamosa County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Alamosa's 5,098 acreswhy one lot differs from the next →
- Which side of Alamosa you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 5,098 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.3 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Alamosa-wide figureread your own land →
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