Denver County, in Colorado, sits in USDA hardiness zone 6a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Expect colorado blue spruce, tomato, penstemon, and apple to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Denver County lies within the Front Range and the High Plains — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Denver County holds more than one microclimate.
Soils and elevations shift across Denver County, so your frost dates and drainage aren't the county average. 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
Last Hard Freeze (28°F)
Apr 9
County normal — light frosts run a few weeks later
First Hard Freeze (28°F)
Oct 29
County normal — light frosts arrive a few weeks earlier
County Area
98K acres
Hardiness Zone Range
Zone maps are averages across Denver County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in Denver County
Across Denver County, the ground is predominantly Mollisols, where Elyria, Truckton, and Ascalon are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.0–7.4, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Mollisols
Drainage
Well drained
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
What Grows in Denver County
Plants matched to Denver County's USDA zones 6a — each links to its full growing profile.
Is it too late to plant in Denver County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 12; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 9 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 29 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
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.
Safe to Grow Here?
What the federal record shows across Denver County — and how to grow with it.
We checked the federal record across Denver County — 2,786 documented sites across 5 of the 9 source types we track.
The most significant on record: 31 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Denver County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Sources Checked
across Denver County
Severity Distribution
across Denver County
Highest-Severity Sites
Know Before You Grow
- •Underground tanks can leak petroleum products. Soil testing near former gas stations is recommended.
- •Raised beds with imported soil can reduce exposure risk near brownfield sites.
- •TRI facilities report chemical releases. Check wind direction — downwind parcels face higher airborne exposure.
Check your specific parcel in Denver County
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
Denver County Average
- ●USDA Zones 6a
- ●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 parcel in Denver County
Pull a site-specific report for your exact address in Denver County, 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 Denver County, Colorado
- USDA Hardiness Zones: 6a (USDA PHZM 2023)
- Last Hard Freeze (28°F): Apr 9 (county normal, NOAA 1991–2020 Climate Normals — light frosts can follow for a few weeks)
- First Hard Freeze (28°F): Oct 29 (county normal, NOAA 1991–2020 Climate Normals — light frosts can arrive a few weeks earlier)
- Days Between Hard Freezes: ~203 (county normal, NOAA 1991–2020 Climate Normals)
- County Land Area: 98K acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. County boundaries: US Census TIGER/Line 2025.
Frost dates here are the Denver County average. Low spots and tree cover move them by days on any one yard — see your exact frost windows.
Frequently Asked Questions
What hardiness zone is Denver County, Colorado?
Denver County sits in USDA hardiness zone 6a, 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 Denver County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 12; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 9 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 29 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
When does frost risk typically end in Denver County?
The last hard freeze (28°F) in Denver County typically lands around Apr 9, 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.
How long is the growing season in Denver County?
Measured between 28°F hard freezes, Denver County sees about 203 frost-free days — roughly Apr 9 through Oct 29, per NOAA 1991–2020 climate normals. Tender crops get a somewhat shorter practical window, since lighter frosts reach a few weeks past the hard-freeze dates on both ends.
What vegetables grow in Denver County?
Denver County's zone 6a supports 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 Denver County, really?
Officially, Denver County sits in USDA zone 6a (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 Denver County?
The federal record around Denver County runs heavier than most — 2,786 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.
Just moved to Denver County — what should I know before planting?
Start with three facts. Denver County sits in USDA zone 6a, which sets what survives winter; the last 28°F hard freeze typically clears around Apr 9, with about 203 frost-free days to work with (NOAA 1991–2020 climate normals); and 2,786 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything on this page is a Denver County 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.
Will It Grow Here?
Zone fit is the first question — each answer below reads Colorado's frost window, season length, and soil profile against the plant's real requirements.