Alma, Colorado, sits in USDA hardiness zones 6a-7b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
On paper, colorado blue spruce, tomato, penstemon, and apple all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Even in Alma, 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 Alma lot. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Quick Facts
USDA Zones
6a-7b
Last Hard Freeze (28°F)
May 23
Town normal — light frosts run a few weeks later
First Hard Freeze (28°F)
Sep 26
Town normal — light frosts arrive a few weeks earlier
Town Area
278 acres
Hardiness Zone Range
Zone maps are averages across Alma. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil varies lot by lot — soil types explained.
What Grows in Alma
Plants matched to Alma's USDA zones 6a-7b — each links to its full growing profile.
Is it too late to plant in Alma?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Apr 25; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 23 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 26 — long-season crops need about 90 days of runway, quick greens only 30. When the window is tight, the fall moves are quick ones — baby greens, radishes, and garlic set for next season.
Growing Challenges in Colorado
What an experienced grower plans around here — each one has a move.
Low annual rainfall (7-20 inches) means irrigation is essential nearly everywhere
Build the irrigation first — drip plus mulch makes a high-desert garden run on remarkably little water.
High altitude UV and temperature swings stress plants
Harden transplants gradually, shade-cloth their first high-sun week, and keep row covers handy for cold nights.
Very short growing season at elevation (60-90 frost-free days above 8,000 ft)
Above 8,000 feet, count your real frost-free days and choose varieties bred to finish inside them.
Alkaline soils (pH 7.5-8.5) limit acid-loving plants without amendment
A soil test tells you your actual pH — grow acid-lovers in containers of amended mix while the native ground grows everything else.
For cultivar selection, pest pressure, and planting-time guidance specific to Colorado, the Colorado State University Extension is the authoritative local source.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Sources Checked
within ~10 miles of Alma
Severity Distribution
within ~10 miles of Alma
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Alma, two things run higher than the national average — Mining (222 sites) and Nitrate (122 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Alma
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
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.
25+ data sources analyzed in seconds
Your Specific Parcel Matters
Alma Average
- ●USDA Zones 6a-7b
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Alma
Pull a site-specific report for your exact address in Alma, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
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.
25+ data sources analyzed in seconds
Key Growing Facts for Alma, Colorado
- USDA Hardiness Zones: 6a-7b (USDA PHZM 2023)
- Last Hard Freeze (28°F): May 23 (town normal, NOAA 1991–2020 Climate Normals — light frosts can follow for a few weeks)
- First Hard Freeze (28°F): Sep 26 (town normal, NOAA 1991–2020 Climate Normals — light frosts can arrive a few weeks earlier)
- Days Between Hard Freezes: ~126 (town normal, NOAA 1991–2020 Climate Normals)
- Land Area: 278 acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. Boundaries: US Census TIGER/Line 2025.
Frequently Asked Questions
What hardiness zone is Alma, Colorado?
Alma sits in USDA hardiness zones 6a-7b, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
Is it too late to plant in Alma?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Apr 25; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 23 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 26 — long-season crops need about 90 days of runway, quick greens only 30. When the window is tight, the fall moves are quick ones — baby greens, radishes, and garlic set for next season.
When does frost risk typically end in Alma?
The last hard freeze (28°F) in Alma typically lands around May 23, per NOAA 1991–2020 climate normals — an earlier marker than the light-frost dates many planting charts quote. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
When is the first frost in Alma?
The first hard freeze (28°F) in Alma typically arrives around Sep 26, per NOAA 1991–2020 climate normals — the point most tender summer crops finish. Lighter frosts usually reach a couple of weeks earlier, so watch the forecast from late summer on and harvest or cover tender plants before the first cold night.
What vegetables grow in Alma?
Alma's zones 6a-7b support a wide range — strong performers include Colorado Blue Spruce, Tomato, Penstemon, Apple, and Peach. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is Alma, really?
Officially, Alma sits in USDA zones 6a-7b (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in Alma?
The federal record around Alma runs heavier than most — 366 documented sites — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do gardeners stretch the season in Alma?
With about 126 frost-free days between hard freezes, Alma rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder, cold frames and low tunnels more, and quick-maturing varieties make the arithmetic work. Starting transplants indoors ahead of the May 23 hard-freeze normal stretches the season without touching the calendar.
Everything on this page is a Alma average. Your yard writes its own version — we read soil, sun, drainage, and frost at your exact address. Try it for 14 days — no card required.