Douglas County, in Colorado, sits in USDA hardiness zone 5b — a zone band wide enough that plant choice, not possibility, is the interesting question.
The conditions favor cabbage, cranberry, lavender, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Douglas County lies within the Front Range — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Douglas County holds more than one microclimate.
Soils and elevations shift across Douglas 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 Douglas County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Douglas County — the short answer
Douglas County, Colorado: USDA zone 5b, about 161 days between hard freezes, across 538K acres.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 3
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 11
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~161
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 538K 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 5b is Douglas County's average, not your lot's — a low corner or a tree line moves it. Against Douglas County's 161-day season, see what your own ground reads.
Heat in Douglas County
Across a year, Douglas County accumulates about 2,029 growing degree days above 50°F, about 197 more than the middle Colorado county — ahead of 34 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 Douglas County
Across Douglas County, the ground is predominantly Mollisols, where Sphinx, Fondis, and Bresser are the most extensive named soil series. The soil is generally well drained with a sandy loam surface. Topsoil pH runs about 6.7–7.0, neutral. Rainfall drains through hydrologic group D soils.
Soil order
Mollisols
Drainage
Well drained
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
How the ground varies across Douglas County
The USDA soil survey maps 67% of Douglas County as well drained — but another 31% drains differently: 29% somewhat excessively drained, 2% poorly drained.
Sphinx is the most extensive named soil at 19% of mapped acres, then Fondis (10%) and Bresser (6%).
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 Douglas County
Each reading below is measured for Douglas 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 Douglas County are well drained, in hydrologic group D — 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 Douglas County runs about pH 6.7–7.0, 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
MeasuredDouglas County runs about 161 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
MeasuredDouglas County sits in USDA hardiness zone 5b.
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 Douglas County is in
Douglas County spans 3 EPA Level III ecoregions — Southwestern Tablelands (55%), Southern Rockies (34%) and High Plains (11%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Douglas County
We scored all 1,086 plants against Douglas County's own USDA zone 5b and its own 161-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 Douglas County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 5; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 11 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Documented around Douglas County
- Japanese beetle3 documented records
- monarch butterfly2 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Douglas County
USGS estimates 8,204 lb of Glyphosate on Douglas County farmland in 2019, its largest by weight, ahead of 2,4-d (2,902 lb) and Dicamba (1,664 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 Douglas County — and how to grow with it.
We checked the federal record across Douglas County — 660 documented sites across 7 of the 9 source types we track.
The most significant on record: 3 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Douglas 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.
What's on the federal record near Douglas County
Closest first, across Douglas County. Listing isn't leaking, and distance isn't exposure.
- SC00806721AAB DAWMAS03Nitrate · 2.5 mi
- Allis Ranch PreserveUnderground Storage Tanks · 2.7 mi
- CASTLE ROCK TOWN OFPFAS · 3.3 mi
- Elvins Rentals & Storage IncUnderground Storage Tanks · 3.6 mi
- CIRCLE K STORE # 2709860Brownfields · 3.6 mi
- Plum Creek Golf ClubUnderground Storage Tanks · 3.7 mi
- FA CO CR CHRYS LLCBrownfields · 3.9 mi
- Alta #6104Underground Storage Tanks · 4.1 mi
- BROOKSIDE INN SKILLED NURSING & REHABBrownfields · 4.2 mi
- Sav-O-Mat IncUnderground Storage Tanks · 4.2 mi
- AGGREGATE INDUSTRIES - CASTLE ROCK PLANTToxics Release Inventory · 4.2 mi
- BROOKSIDE REHABILITATION AND WELLNESSBrownfields · 4.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Douglas 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 Douglas County.
Total Sites
660
across Douglas County
Risk Level
High
Highest-severity
3 Superfund sites (none NPL-listed)
Sources Checked
across Douglas County
Severity Distribution
across Douglas County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Douglas County, PFAS runs higher than the national average — 12 sites across Douglas County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check your specific parcel in Douglas 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 Douglas County average
Your land is one point inside Douglas County
Everything above resolves to Douglas County as a whole — one PHZM band and one county frost record, read across 538K 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 Douglas County Average
Douglas County Average
- ●USDA Zones 5b, averaged across Douglas County
- ●One soil character for all of Douglas County
- ●Frost dates read at Douglas County's scale: May 3 to Oct 11
YOUR Parcel
- ✓Your exact zone, not Douglas County's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Douglas County
Pull a site-specific report for your exact address in Douglas County, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Douglas County averages can't show:
We read public map data around Douglas County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Douglas County average
How we know this about Douglas 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 Douglas County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Douglas County
When does frost risk typically end in Douglas County?
The last hard freeze (28°F) in Douglas County typically lands around May 3, 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 24.
How long is the growing season in Douglas County?
Measured between 28°F hard freezes, Douglas County sees about 161 frost-free days — roughly May 3 through Oct 11, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 24 to Sep 27, about 126 days.
Is the soil safe to grow vegetables in Douglas County?
The federal record around Douglas County runs heavier than most — 660 documented sites, mostly Underground Storage Tanks entries (249), the nearest Nitrate record about 2.5 miles out — 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.
Everything above is measured at Douglas County's scale — its 5b band and its 161-day season. Your yard writes its own version of Douglas 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 Douglas County’s own scale
9 of the readings below were taken at Douglas County's own scale — its own ~161-day span between 28°F freezes, the 3 most extensive soil series mapped here and 660 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Douglas County's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Douglas County's own 28°F hard-freeze dates and its ~161-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Douglas CountyUSDA NRCS SSURGO
- 660 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 2.5 miles outFederal environmental registers
- Douglas County's boundary and the 538,168 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~161-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions Douglas County spans, Southwestern Tablelands the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Douglas County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Douglas 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 Douglas County — the ~161 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 Douglas County's 538,168 acreswhy one lot differs from the next →
- Which of those 660 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 Douglas Countyread your own land →