What Growing Zone Is Colorado In?
USDA hardiness zones
4b to 7a
2023 USDA Plant Hardiness Zone Map
Colorado spans USDA hardiness zone 4b to 7a across its major population centers, according to the 2023 USDA Plant Hardiness Zone Map. That's a real range, not a single number: where you fall in it depends on where in the state you actually are.
Hardiness zone for ZIP 80202 (Denver)
Your USDA hardiness zone
Zone 6a
Avg. annual minimum (°F)
-10°F to -5°F
Avg. annual minimum (°C)
-23°C to -21°C
Nearest reference point: Denver, CO
This is a regional estimate based on the nearest of 826 reference points, each matched to the official 2023 USDA zone map. It’s accurate to within about a half-zone across most of the country, but elevation shifts zones over short distances, so if you’re in mountainous terrain, check the official USDA map for your exact address (see Sources below).
Colorado's USDA Hardiness Zones
Here's how the zone shifts across Colorado's major cities:
For your exact zone by ZIP code, use the Hardiness Zone Finder, and for what a zone number actually measures (and doesn't), see how zones actually work.
Frost Dates in Colorado
Frost dates track zone, so they shift across Colorado the same way the zone number does:
- San Luis Valley (Alamosa) (zone 4): average last frost Apr 23 - May 7, average first frost Sep 23 - Oct 7.
- Western slope (Grand Junction) (zone 7): average last frost Mar 18 - Apr 1, average first frost Oct 29 - Nov 12.
These are averages, not guarantees. For your specific frost window, use the Frost Date Calculator. For a full vegetable-by-vegetable planting calendar already calculated from Colorado's frost dates, see the Colorado Planting Calendar.
The San Luis Valley (Alamosa, zone 4b) is a high intermontane basin where cold, dense air drains and pools on clear nights, producing strong temperature inversions -- subzero lows are common most winters, per the Colorado Climate Center at CSU.
What Grows Well in Colorado's Zones
A few real, zone-appropriate picks recommended by Colorado State University Extension for Colorado landscapes: not an exhaustive list, but a genuine starting point.
- Rocky Mountain juniper (Juniperus scopulorum)
- Pinyon pine (Pinus edulis)
- Apache plume (Fallugia paradoxa)
- Threeleaf sumac (Rhus trilobata)
- Common lilac (Syringa vulgaris)
- Curlleaf mountain-mahogany (Cercocarpus ledifolius)
Ready to find your exact zone? Use the Hardiness Zone Finder: enter your ZIP code for a precise match against the 2023 USDA map.
Colorado Growing Zone FAQ
What growing zone is Colorado in?
Colorado spans USDA hardiness zones 4b to 7a on the 2023 USDA Plant Hardiness Zone Map. Alamosa is zone 4b and Denver is zone 6a; enter your ZIP code in the Hardiness Zone Finder for your exact zone.
What growing zone is Denver, CO?
Denver is in USDA hardiness zone 6a on the 2023 USDA map. Zones within a city can differ by half a zone, so check your ZIP code for an exact match.
What growing zone is Fort Collins, CO?
Fort Collins is in USDA hardiness zone 5b on the 2023 USDA map. Zones within a city can differ by half a zone, so check your ZIP code for an exact match.
What growing zone is Boulder, CO?
Boulder is in USDA hardiness zone 6a on the 2023 USDA map. Zones within a city can differ by half a zone, so check your ZIP code for an exact match.
What growing zone is Alamosa, CO?
Alamosa is in USDA hardiness zone 4b on the 2023 USDA map. Zones within a city can differ by half a zone, so check your ZIP code for an exact match.
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The Spacing & Planting Cheat Sheet
When to start, when to plant, how far apart.
Sources & further reading
Zone and city data checked against the official USDA Plant Hardiness Zone Map. Plant recommendations sourced from Colorado State University Extension. Climate note sourced from Colorado Climate Center, Colorado State University. For more on how we build and verify reference data across this site, see our methodology page.
Growing zones in nearby states
Gardening near a state line? Zones don't stop at the border:
- Arizona growing zones
- Oklahoma growing zones
- Utah growing zones
- Kansas growing zones
- New Mexico growing zones
- Nebraska growing zones
Or browse all 51 state growing-zone guides.