Dolores County, in Colorado, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Crops well matched to these conditions include cabbage, blackberry, california poppy, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Dolores County lies within the Four Corners / Southwest Colorado — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Dolores County holds more than one microclimate.
Soils and elevations shift across Dolores 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 Dolores County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Dolores County — the short answer
Dolores County, Colorado: USDA zone 6a, about 146 days between hard freezes, across 683K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 15
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 8
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~146
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 683K 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 Dolores County's average, not your lot's — a low corner or a tree line moves it. Against Dolores County's 146-day season, see what your own ground reads.
Heat in Dolores County
Across a year, Dolores County accumulates about 1,266 growing degree days above 50°F, about 566 fewer than the middle Colorado county — ahead of 23 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 Dolores County
Across Dolores County, the ground is predominantly Alfisols, where Wetherill, Needleton, and Frisco are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 6.7–7.4, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Well drained
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
How the ground varies across Dolores County
The USDA soil survey maps 94% of Dolores County as well drained — but another 4% drains differently: 2% excessively drained, 1% somewhat poorly drained.
Wetherill is the most extensive named soil at 7% of mapped acres, then Needleton (4%) and Frisco (4%).
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 Dolores County
Each reading below is measured for Dolores 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 Dolores 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 Dolores County runs about pH 6.7–7.4, 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
MeasuredDolores County runs about 146 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredDolores 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 Dolores County is in
Dolores County spans 2 EPA Level III ecoregions — Southern Rockies (61%) and Colorado Plateaus (39%). 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 Dolores County
We scored all 1,086 plants against Dolores County's own USDA zone 6a and its own 146-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 Dolores 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 Apr 17; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 8 — long-season crops need about 90 days of runway, quick greens only 30. Even here the calendar’s edges hold value: thirty-day greens late in the window, then garlic and a rested bed for spring.
What gets applied to farmland in Dolores County
USGS estimates 14,571 lb of Glyphosate on Dolores County farmland in 2019, its largest by weight, ahead of Bentazone (4,160 lb) and Atrazine (3,078 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 Dolores County — and how to grow with it.
We checked the federal record across Dolores County — 166 documented sites across 5 of the 9 source types we track.
The most significant on record: 1 Superfund site (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Dolores 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 Dolores County
Closest first, across Dolores County. Listing isn't leaking, and distance isn't exposure.
- TeaserMining · 14.6 mi
- Little SilverMining · 15.8 mi
- Bruce Auto & PaintUnderground Storage Tanks · 17.3 mi
- PrivateerMining · 17.5 mi
- AIR PRODUCTS HELIUM INCBrownfields · 17.8 mi
- DOLORES TOWN OFPFAS · 20.9 mi
- Geyser GroupMining · 20.9 mi
- Rosebud MineMining · 21.0 mi
- NettieMining · 21.7 mi
- Marriage StakeMining · 21.7 mi
- AT&T DOVE CREEK RBrownfields · 21.7 mi
- UnknownMining · 21.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dolores 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 Dolores County.
Sources Checked
across Dolores County
Severity Distribution
across Dolores County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dolores County, Mining runs higher than the national average — 141 sites across Dolores County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Dolores 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 Dolores County average
Your land is one point inside Dolores County
Everything above resolves to Dolores County as a whole — one PHZM band and one county frost record, read across 683K 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 Dolores County Average
Dolores County Average
- ●USDA Zones 6a, averaged across Dolores County
- ●One soil character for all of Dolores County
- ●Frost dates read at Dolores County's scale: May 15 to Oct 8
YOUR Parcel
- ✓Your exact zone, not Dolores County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Dolores County
Pull a site-specific report for your exact address in Dolores County, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dolores County averages can't show:
We read public map data around Dolores County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dolores County average
How we know this about Dolores 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 Dolores County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Dolores County
When does frost risk typically end in Dolores County?
The last hard freeze (28°F) in Dolores County typically lands around May 15, 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 Jun 5.
How long is the growing season in Dolores County?
Measured between 28°F hard freezes, Dolores County sees about 146 frost-free days — roughly May 15 through Oct 8, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 5 to Sep 24, about 111 days.
Is the soil safe to grow vegetables in Dolores County?
The federal record around Dolores County runs heavier than most — 166 documented sites, mostly Mining entries (141), the nearest Mining record about 15 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.
How do gardeners stretch the season in Dolores County?
With about 146 frost-free days between hard freezes, Dolores County rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 174 to 202 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 15 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Dolores County's scale — its 6a band and its 146-day season. Your yard writes its own version of Dolores 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 Dolores County’s own scale
8 of the readings below were taken at Dolores County's own scale — its own ~146-day span between 28°F freezes, the 3 most extensive soil series mapped here and 166 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Dolores County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Dolores County's own 28°F hard-freeze dates and its ~146-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Dolores CountyUSDA NRCS SSURGO
- 166 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Mining record about 15 miles outFederal environmental registers
- Dolores County's boundary and the 682,988 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~146-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Dolores County spans, Southern Rockies the largestUS EPA Level III Ecoregions
- Which agricultural compounds go onto Dolores 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 Dolores County — the ~146 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 Dolores County's 682,988 acreswhy one lot differs from the next →
- Which of those 166 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 Dolores Countyread your own land →