Broomfield 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.
Growers here do well with cabbage, hazelnut, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Broomfield 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
Broomfield County holds more than one microclimate.
Soils and elevations shift across Broomfield 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 Broomfield County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Broomfield County — the short answer
Broomfield County, Colorado: USDA zone 6a, about 184 days between hard freezes, across 21K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 19
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 20
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~184
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 21K 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 Broomfield County's average, not your lot's — a low corner or a tree line moves it. Against Broomfield County's 184-day season, see what your own ground reads.
Heat in Broomfield County
Across a year, Broomfield County accumulates about 2,602 growing degree days above 50°F, about 770 more than the middle Colorado county — ahead of 46 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 Broomfield County
Across Broomfield County, the ground is predominantly Mollisols, where Platner, Nunn, and Ulm are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 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 Broomfield County
The USDA soil survey maps 90% of Broomfield County as well drained — but another 9% drains differently: 7% somewhat excessively drained, 1% poorly drained.
Platner is the most extensive named soil at 28% of mapped acres, then Nunn (20%) and Ulm (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 Broomfield County
Each reading below is measured for Broomfield 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 Broomfield 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 Broomfield County runs about pH 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
MeasuredBroomfield County runs about 184 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
MeasuredBroomfield 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 Broomfield County is in
Broomfield 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 Broomfield County
We scored all 1,086 plants against Broomfield County's own USDA zone 6a and its own 184-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 Broomfield County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 22; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 19 (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. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
Documented around Broomfield County
- Japanese beetle1 documented records
- monarch butterfly10 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Broomfield County
USGS estimates 5,376 lb of Glyphosate on Broomfield County farmland in 2019, its largest by weight, ahead of 2,4-d (1,974 lb) and Atrazine (1,468 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 Broomfield County — and how to grow with it.
We checked the federal record across Broomfield County — 162 documented sites across 4 of the 9 source types we track.
The most significant on record: 15 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Broomfield County is a modest one — a typical footprint for a growing area. Nothing here calls for alarm; it's worth knowing which recorded sites sit closest to where you grow, and each one on the map carries its type and location. If one turns out to be a near neighbor, a one-time soil test settles the question.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Broomfield County
Closest first, across Broomfield County. Listing isn't leaking, and distance isn't exposure.
- Safeway Fuel Center #2624Underground Storage Tanks · 0.8 mi
- SAFEWAY INC. - #2624Brownfields · 0.9 mi
- Buggy Bath Car WashUnderground Storage Tanks · 1.0 mi
- NMFRA Station #64Underground Storage Tanks · 1.2 mi
- BROOMFIELD SKILLED NURSING AND REHABILITATION CENTERBrownfields · 1.6 mi
- 7-Eleven #27551Underground Storage Tanks · 1.8 mi
- BROOMFIELD HEIGHTS MIDDLE SCHOOLBrownfields · 1.8 mi
- 7-Eleven #35336Underground Storage Tanks · 1.9 mi
- Huskey Service StationUnderground Storage Tanks · 2.0 mi
- Hearts Jiffy Stop IncUnderground Storage Tanks · 2.0 mi
- King Soopers Fuel Facility #718Underground Storage Tanks · 2.0 mi
- Alta #6140Underground Storage Tanks · 2.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Broomfield 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 Broomfield County.
Total Sites
162
across Broomfield County
Risk Level
Moderate
Highest-severity
15 Toxics Release Inventory facilities
Sources Checked
across Broomfield County
Severity Distribution
across Broomfield County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Broomfield County, Toxics Release Inventory runs higher than the national average — 15 sites across Broomfield County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Broomfield 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 Broomfield County average
Your land is one point inside Broomfield County
Everything above resolves to Broomfield County as a whole — one PHZM band and one county frost record, read across 21K 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 Broomfield County Average
Broomfield County Average
- ●USDA Zones 6a, averaged across Broomfield County
- ●One soil character for all of Broomfield County
- ●Frost dates read at Broomfield County's scale: Apr 19 to Oct 20
YOUR Parcel
- ✓Your exact zone, not Broomfield County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Broomfield County
Pull a site-specific report for your exact address in Broomfield County, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Broomfield County averages can't show:
We read public map data around Broomfield County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Broomfield County average
How we know this about Broomfield 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 Broomfield County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Broomfield County
When does frost risk typically end in Broomfield County?
The last hard freeze (28°F) in Broomfield County typically lands around Apr 19, 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 10.
How long is the growing season in Broomfield County?
Measured between 28°F hard freezes, Broomfield County sees about 184 frost-free days — roughly Apr 19 through Oct 20, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 10 to Oct 6, about 149 days.
Is the soil safe to grow vegetables in Broomfield County?
The federal record around Broomfield County shows 162 documented sites, mostly Brownfields entries (77), the nearest Underground Storage Tanks record about 0.8 miles out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
Everything above is measured at Broomfield County's scale — its 6a band and its 184-day season. Your yard writes its own version of Broomfield 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 Broomfield County’s own scale
9 of the readings below were taken at Broomfield County's own scale — its own ~184-day span between 28°F freezes, the 3 most extensive soil series mapped here and 162 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Broomfield County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Broomfield County's own 28°F hard-freeze dates and its ~184-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Broomfield CountyUSDA NRCS SSURGO
- 162 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 0.8 miles outFederal environmental registers
- Broomfield County's boundary and the 21,099 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~184-day seasonGrowable Ground crop-matching engine
- Broomfield County sitting wholly inside the High PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Broomfield County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Broomfield 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 Broomfield County — the ~184 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 Broomfield County's 21,099 acreswhy one lot differs from the next →
- Which of those 162 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 Broomfield Countyread your own land →