Delta County, in Colorado, sits in USDA hardiness zone 7a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Well-matched crops include cabbage, pawpaw, california poppy, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Delta County lies within the Uncompahgre Valley — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Delta County holds more than one microclimate.
Soils and elevations shift across Delta 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 Delta County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Delta County — the short answer
Delta County, Colorado: USDA zone 7a, about 189 days between hard freezes, across 731K acres.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 17
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 23
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~189
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 731K 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 7a is Delta County's average, not your lot's — a low corner or a tree line moves it. Against Delta County's 189-day season, see what your own ground reads.
Heat in Delta County
Across a year, Delta County accumulates about 2,545 growing degree days above 50°F, about 713 more than the middle Colorado county — ahead of 43 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 Delta County
Across Delta County, the ground is predominantly Aridisols, where Agua Fria, Delson, and Utaline are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.2–8.2, slightly alkaline. Rainfall drains through hydrologic group C soils.
Soil order
Aridisols
Drainage
Well drained
Hydric soils
3%
Soil still varies lot by lot — soil types explained.
How the ground varies across Delta County
The USDA soil survey maps 85% of Delta County as well drained — but another 3% drains differently: 1% poorly drained, 1% somewhat poorly drained.
Agua Fria is the most extensive named soil at 12% of mapped acres, then Delson (9%) and Utaline (7%).
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 Delta County
Each reading below is measured for Delta 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 Delta 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 Delta County runs about pH 7.2–8.2, on the alkaline side.
Many vegetables cope, but acid-lovers like blueberries struggle, and iron and manganese lock up above about pH 7.5 — leaves yellow between the veins even in rich soil.
Elemental sulfur and generous organic matter lower pH slowly for the beds that need it; test first so you add only what the soil actually calls for.
USDA NRCS SSURGO
Season length
MeasuredDelta County runs about 189 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
MeasuredDelta County sits in USDA hardiness zone 7a.
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 Delta County is in
Delta County spans 2 EPA Level III ecoregions — Colorado Plateaus (64%) and Southern Rockies (36%). 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 Delta County
We scored all 1,086 plants against Delta County's own USDA zone 7a and its own 189-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 Delta 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 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 17 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 23 — 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 Delta County
- monarch butterfly4 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Delta County
USGS estimates 22,179 lb of Glyphosate on Delta County farmland in 2019, its largest by weight, ahead of Dicamba (6,027 lb) and Atrazine (4,743 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 Delta County — and how to grow with it.
We checked the federal record across Delta County — 158 documented sites across 6 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.
There's a meaningful federal record across Delta 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 Delta County
Closest first, across Delta County. Listing isn't leaking, and distance isn't exposure.
- Austins Conoco ServiceUnderground Storage Tanks · 3.9 mi
- Go-Fer Foods CedaredgeUnderground Storage Tanks · 4.0 mi
- CDOT CedaredgeUnderground Storage Tanks · 4.0 mi
- Orchard City ServiceUnderground Storage Tanks · 4.0 mi
- Former BJ's Express Gas LlcUnderground Storage Tanks · 4.0 mi
- Triple Treat SinclairUnderground Storage Tanks · 4.1 mi
- Cedaredge ServiceUnderground Storage Tanks · 4.1 mi
- Service StationUnderground Storage Tanks · 4.1 mi
- Moze Floral ShopUnderground Storage Tanks · 4.2 mi
- Spruce LodgeUnderground Storage Tanks · 4.3 mi
- Austins ConocoUnderground Storage Tanks · 4.9 mi
- Silver State ServiceUnderground Storage Tanks · 5.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Delta 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 Delta County.
Total Sites
158
across Delta County
Risk Level
Elevated
Highest-severity
3 Superfund sites (none NPL-listed)
Sources Checked
across Delta County
Severity Distribution
across Delta County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Delta County, two things run higher than the national average across Delta County — Superfund (3 sites) and Underground Storage Tanks (101 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Delta 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 Delta County average
Your land is one point inside Delta County
Everything above resolves to Delta County as a whole — one PHZM band and one county frost record, read across 731K 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 Delta County Average
Delta County Average
- ●USDA Zones 7a, averaged across Delta County
- ●One soil character for all of Delta County
- ●Frost dates read at Delta County's scale: Apr 17 to Oct 23
YOUR Parcel
- ✓Your exact zone, not Delta County's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Delta County
Pull a site-specific report for your exact address in Delta County, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Delta County averages can't show:
We read public map data around Delta County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Delta County average
How we know this about Delta 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 Delta County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Delta County
When does frost risk typically end in Delta County?
The last hard freeze (28°F) in Delta County typically lands around Apr 17, 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 8.
How long is the growing season in Delta County?
Measured between 28°F hard freezes, Delta County sees about 189 frost-free days — roughly Apr 17 through Oct 23, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 8 to Oct 9, about 154 days.
Is the soil safe to grow vegetables in Delta County?
The federal record around Delta County is a meaningful one — 158 documented sites, mostly Underground Storage Tanks entries (101), the nearest Underground Storage Tanks record about 3.9 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 Delta County's scale — its 7a band and its 189-day season. Your yard writes its own version of Delta 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 Delta County’s own scale
9 of the readings below were taken at Delta County's own scale — its own ~189-day span between 28°F freezes, the 3 most extensive soil series mapped here and 158 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Delta County's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Delta County's own 28°F hard-freeze dates and its ~189-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Delta CountyUSDA NRCS SSURGO
- 158 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 3.9 miles outFederal environmental registers
- Delta County's boundary and the 730,960 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~189-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Delta County spans, Colorado Plateaus the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Delta County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Delta 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 Delta County — the ~189 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 Delta County's 730,960 acreswhy one lot differs from the next →
- Which of those 158 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 Delta Countyread your own land →