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 cabbage, hazelnut, lavender, and collard greens 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 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Denver County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Denver County — the short answer
Denver County, Colorado: USDA zone 6a, about 183 days between hard freezes, across 98K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 20
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 20
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~183
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 98K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 6a is Denver County's average, not your lot's — a low corner or a tree line moves it. Against Denver County's 183-day season, see what your own ground reads.
Heat in Denver County
Across a year, Denver County accumulates about 2,692 growing degree days above 50°F, about 860 more than the middle Colorado county — ahead of 48 of Colorado’s 64 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
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.
How the ground varies across Denver County
The USDA soil survey maps 58% of Denver County as well drained — but another 3% drains differently: 3% somewhat excessively drained.
Elyria is the most extensive named soil at 14% of mapped acres, then Truckton (12%) and Ascalon (10%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Denver County
Each reading below is measured for Denver County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Denver County are well drained, in hydrologic group C — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Denver County runs about pH 7.0–7.4, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredDenver County runs about 183 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredDenver County sits in USDA hardiness zone 6a.
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 Denver County is in
Denver County sits in the High Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Denver County
We scored all 1,086 plants against Denver County's own USDA zone 6a and its own 183-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Colorado 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 23; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 20 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 20 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
Documented around Denver County
- Japanese beetle93 documented records
- monarch butterfly16 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Denver County
USGS estimates 13,876 lb of Glyphosate on Denver County farmland in 2019, its largest by weight, ahead of 2,4-d (9,138 lb) and Dicamba (2,109 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
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.
There's a meaningful federal record across Denver County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Denver County
Closest first, across Denver County. Listing isn't leaking, and distance isn't exposure.
- CCOD Stapleton Int'l Airport Main BoilerUnderground Storage Tanks · 450 ft
- Sam's Club #4777Underground Storage Tanks · 0.6 mi
- Continental AirlinesUnderground Storage Tanks · 0.6 mi
- Vehicle Maintenance CenterUnderground Storage Tanks · 0.6 mi
- FAA Rrv LocUnderground Storage Tanks · 0.6 mi
- Amr Combs - 141Underground Storage Tanks · 0.6 mi
- Delta Air LinesUnderground Storage Tanks · 0.6 mi
- BraniffUnderground Storage Tanks · 0.6 mi
- Western AirlinesUnderground Storage Tanks · 0.6 mi
- FAA Stapleton Dend RtrUnderground Storage Tanks · 0.6 mi
- FAA Rrv RvrUnderground Storage Tanks · 0.6 mi
- Spo LocUnderground Storage Tanks · 0.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Denver County'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 Denver County.
Sources Checked
across Denver County
Severity Distribution
across Denver County
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •TRI facilities report what they release. Check the wind — downwind beds catch more of it.
Check your specific parcel in Denver County
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 Denver County average
Your land is one point inside Denver County
Everything above resolves to Denver County as a whole — one PHZM band and one county frost record, read across 98K 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 county 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 county average.
Your Lot vs the Denver County Average
Denver County Average
- ●USDA Zones 6a, averaged across Denver County
- ●One soil character for all of Denver County
- ●Frost dates read at Denver County's scale: Apr 20 to Oct 20
YOUR Parcel
- ✓Your exact zone, not Denver County's 6a
- ✓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 lot that Denver County averages can't show:
We read public map data around Denver County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Denver County average
How we know this about Denver County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Denver County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Denver County
When does frost risk typically end in Denver County?
The last hard freeze (28°F) in Denver County typically lands around Apr 20, 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 May 11.
How long is the growing season in Denver County?
Measured between 28°F hard freezes, Denver County sees about 183 frost-free days — roughly Apr 20 through Oct 20, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 11 to Oct 6, about 148 days.
Is the soil safe to grow vegetables in Denver County?
The federal record around Denver County is a meaningful one — 2,786 documented sites, mostly Underground Storage Tanks entries (1,694), the nearest Underground Storage Tanks record under a tenth of a mile 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.
Everything above is measured at Denver County's scale — its 6a band and its 183-day season. Your yard writes its own version of Denver County's numbers: 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.
What this page reads at Denver County’s own scale
9 of the readings below were taken at Denver County's own scale — its own ~183-day span between 28°F freezes, the 3 most extensive soil series mapped here and 2,786 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Denver County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Denver County's own 28°F hard-freeze dates and its ~183-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Denver CountyUSDA NRCS SSURGO
- 2,786 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record under a tenth of a mile outFederal environmental registers
- Denver County's boundary and the 97,967 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~183-day seasonGrowable Ground crop-matching engine
- Denver County sitting wholly inside the High PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Denver County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Denver County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Colorado grower plans around — written at state scale, so they stay on the state guidefrom Colorado
What this page can’t tell you
- How the season shifts across Denver County — the ~183 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Denver County's 97,967 acreswhy one lot differs from the next →
- Which of those 2,786 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Denver Countyread your own land →