Arapahoe County, in Colorado, sits in USDA hardiness zone 5b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
These conditions suit cabbage, cranberry, lavender, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Arapahoe 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
Arapahoe County holds more than one microclimate.
Soils and elevations shift across Arapahoe 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 Arapahoe County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Arapahoe County — the short answer
Arapahoe County, Colorado: USDA zone 5b, about 173 days between hard freezes, across 511K acres.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 26
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 16
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~173
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 511K 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 Arapahoe County's average, not your lot's — a low corner or a tree line moves it. Against Arapahoe County's 173-day season, see what your own ground reads.
Heat in Arapahoe County
Across a year, Arapahoe County accumulates about 2,492 growing degree days above 50°F, about 660 more than the middle Colorado county — ahead of 42 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 Arapahoe County
Across Arapahoe County, the ground is predominantly Mollisols, where Bresser, Nunn, and Renohill are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.0–7.2, 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 Arapahoe County
The USDA soil survey maps 93% of Arapahoe County as well drained — but another 5% drains differently: 3% somewhat excessively drained, 1% moderately well drained.
Bresser is the most extensive named soil at 11% of mapped acres, then Nunn (9%) and Renohill (9%).
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 Arapahoe County
Each reading below is measured for Arapahoe 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 Arapahoe 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 Arapahoe County runs about pH 7.0–7.2, 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
MeasuredArapahoe County runs about 173 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
MeasuredArapahoe 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 Arapahoe County is in
Arapahoe County spans 2 EPA Level III ecoregions — High Plains (76%) and Southwestern Tablelands (24%). 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 Arapahoe County
We scored all 1,086 plants against Arapahoe County's own USDA zone 5b and its own 173-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 Arapahoe County?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 29; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 16 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
Documented around Arapahoe County
- Japanese beetle14 documented records
- monarch butterfly140 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Arapahoe County
USGS estimates 83,390 lb of Glyphosate on Arapahoe County farmland in 2019, its largest by weight, ahead of 2,4-d (36,813 lb) and Dicamba (19,774 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 Arapahoe County — and how to grow with it.
We checked the federal record across Arapahoe County — 1,813 documented sites across 6 of the 9 source types we track.
The most significant on record: 12 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 Arapahoe 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 Arapahoe County
Closest first, across Arapahoe County. Listing isn't leaking, and distance isn't exposure.
- Keith Hanlon FarmUnderground Storage Tanks · 1.5 mi
- SC00506230CCC ARAPMAS21Nitrate · 5.1 mi
- Strasburg Self Serve GasUnderground Storage Tanks · 6.2 mi
- COLORADO DEPT OF TRANS - STRASBURGBrownfields · 6.3 mi
- Rays Gas & TireUnderground Storage Tanks · 6.4 mi
- Suburban PropaneUnderground Storage Tanks · 6.4 mi
- Intermountain Rural ElectricUnderground Storage Tanks · 6.4 mi
- Petro MatUnderground Storage Tanks · 6.4 mi
- SC00506121ABC ARAPMAS29Nitrate · 6.6 mi
- Arapahoe County Byers ShopUnderground Storage Tanks · 7.1 mi
- Byers Thrift StoreUnderground Storage Tanks · 7.4 mi
- Arthur Perry PropertyUnderground Storage Tanks · 7.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Arapahoe 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 Arapahoe County.
Sources Checked
across Arapahoe County
Severity Distribution
across Arapahoe 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.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Arapahoe 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 Arapahoe County average
Your land is one point inside Arapahoe County
Everything above resolves to Arapahoe County as a whole — one PHZM band and one county frost record, read across 511K 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 Arapahoe County Average
Arapahoe County Average
- ●USDA Zones 5b, averaged across Arapahoe County
- ●One soil character for all of Arapahoe County
- ●Frost dates read at Arapahoe County's scale: Apr 26 to Oct 16
YOUR Parcel
- ✓Your exact zone, not Arapahoe County's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Arapahoe County
Pull a site-specific report for your exact address in Arapahoe County, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Arapahoe County averages can't show:
We read public map data around Arapahoe County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Arapahoe County average
How we know this about Arapahoe 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 Arapahoe County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Arapahoe County
When does frost risk typically end in Arapahoe County?
The last hard freeze (28°F) in Arapahoe County typically lands around Apr 26, 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 17.
How long is the growing season in Arapahoe County?
Measured between 28°F hard freezes, Arapahoe County sees about 173 frost-free days — roughly Apr 26 through Oct 16, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 17 to Oct 2, about 138 days.
Is the soil safe to grow vegetables in Arapahoe County?
The federal record around Arapahoe County is a meaningful one — 1,813 documented sites, mostly Underground Storage Tanks entries (805), the nearest Underground Storage Tanks record about 1.5 miles 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 Arapahoe County's scale — its 5b band and its 173-day season. Your yard writes its own version of Arapahoe 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 Arapahoe County’s own scale
9 of the readings below were taken at Arapahoe County's own scale — its own ~173-day span between 28°F freezes, the 3 most extensive soil series mapped here and 1,813 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Arapahoe County's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Arapahoe County's own 28°F hard-freeze dates and its ~173-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Arapahoe CountyUSDA NRCS SSURGO
- 1,813 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.5 miles outFederal environmental registers
- Arapahoe County's boundary and the 510,647 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~173-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Arapahoe County spans, High Plains the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Arapahoe County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Arapahoe 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 Arapahoe County — the ~173 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 Arapahoe County's 510,647 acreswhy one lot differs from the next →
- Which of those 1,813 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 Arapahoe Countyread your own land →