The Four Corners / Southwest Colorado spans USDA hardiness zones 6a-6b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Southwest Colorado's Four Corners country grows on high-desert mesas at roughly 6,000-7,000 ft, where zone 6a-6b winters meet a warm-day/cool-night rhythm and a late-summer monsoon — a climate distinct from both the lower, warmer valleys of the northern Western Slope and the frost-pocket high country above it. The 146-168 frost-free days around Durango, Cortez, Mancos, and Pagosa Springs favor short-to-mid-season crops, and the Cortez-Dove Creek belt beside Mesa Verde is legendary dryland pinto-bean country (Dove Creek bills itself the "Pinto Bean Capital of the World"). On paper, tomato, colorado blue spruce, apple, and raspberry all suit these conditions — on the ground, soil, sun, and drainage make the final call.
The Four Corners / Southwest Colorado spans Colorado.
Your yard isn't all of the Four Corners / Southwest Colorado.
The Four Corners / Southwest Colorado spans USDA zones 6a-6b, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. 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 Four Corners / Southwest Colorado — soil, climate, flood, and parcel records. How we handle your address.
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The Four Corners / Southwest Colorado — the short answer
The Four Corners / Southwest Colorado: USDA zones 6a-6b, 146–168 frost-free days, in Colorado.
- USDA zones
- 6a-6b
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 146–168 days
- NOAA Regional Climate Centers ACIS, 1991-2020
- Counties
- 4
- US Census TIGER/Line 2025
- Region type
- County cluster
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. Where a region publishes no measured season, no season figure is shown.
Hardiness Zone Range
What Grows in the Four Corners / Southwest Colorado
Plants matched to the Four Corners / Southwest Colorado's USDA zones 6a-6b, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of the Four Corners / Southwest Colorado
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Four Corners / Southwest Colorado’s USDA zones 6a-6b — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across the Four Corners / Southwest Colorado
The USDA soil survey maps this ground county by county. These are those records weighted by land area across four member counties — this region’s own profile, not a state figure.
The ground is predominantly Alfisols, at 37% of mapped acres, followed by Mollisols (25%), Entisols (16%) and Inceptisols (11%). Seven soil orders appear somewhere inside the footprint, which is the honest reason a regional soil answer only goes so far. The most extensive named soils are Wetherill, Needleton, and Romberg.
91% of those acres are well drained, and another 2% excessively drained, 1% somewhat poorly drained. Topsoil pH runs 5.5–7.8 between the lowest and the highest county on record.
Soil order
Alfisols
Drainage
Well drained
Topsoil pH
5.5–7.8
Hydric soils
1%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Archuleta County holds the most wetland ground here, at 2% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Four Corners / Southwest Colorado
The soil survey reads this ground county by county, and the readings above are those records summed across the Four Corners / Southwest Colorado. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records91% of the mapped acres across the Four Corners / Southwest Colorado are well drained — ground that drains quickly. That is area-weighted across all four of its mapped counties.
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
From county recordsTopsoil across the Four Corners / Southwest Colorado runs pH 5.5–7.8 — near neutral in three of its four counties.
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
Safe to Grow Here?
What the federal record shows across the Four Corners / Southwest Colorado — and how to grow with it.
Across the Four Corners / Southwest Colorado's 4 counties the federal record holds 1,029 documented sites, mostly Underground Storage Tanks (327), Nitrate (300) and Mining (286). The heaviest single county is La Plata County, with 486.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to the Four Corners / Southwest Colorado to see which records sit where you actually grow.
Sources Checked
Summed across the 4 counties in the Four Corners / Southwest Colorado
A note from Gnorman
What an experienced grower watches for around here
In and around the Four Corners / Southwest Colorado, two things run higher than the national average across the 4 counties in the Four Corners / Southwest Colorado — Mining (286 sites) and Nitrate (300 sites). 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.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Four Corners / Southwest Colorado
Everything above resolves to the Four Corners / Southwest Colorado as a whole — a footprint spanning USDA zones 6a-6b. Your parcel sits in exactly one of them. 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 region 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 regional average.
Your Lot vs the Four Corners / Southwest Colorado Average
Four Corners / Southwest Colorado Average
- ●USDA Zones 6a-6b, averaged across Four Corners / Southwest Colorado
- ●One soil character for all of Four Corners / Southwest Colorado
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Four Corners / Southwest Colorado's 6a-6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Four Corners / Southwest Colorado
Pull a site-specific report for your exact address in the Four Corners / Southwest Colorado — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Four Corners / Southwest Colorado averages can't show:
We read public map data around The Four Corners / Southwest Colorado — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Four Corners / Southwest Colorado average
How we know this about the Four Corners / Southwest Colorado
The boundary: a cluster of neighboring counties. Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about the Four Corners / Southwest Colorado
What hardiness zone is the Four Corners / Southwest Colorado?
The Four Corners / Southwest Colorado spans USDA hardiness zones 6a-6b, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in the Four Corners / Southwest Colorado?
Measured between 28°F hard freezes, the Four Corners / Southwest Colorado's counties mostly run 149 to 167 frost-free days, median 158 (NOAA Regional Climate Centers ACIS, 1991–2020, over 4 member counties). That 18-day spread is the honest read — no single season describes 4 counties, and each county guide below carries its own.
When does frost risk end in the Four Corners / Southwest Colorado?
Across the Four Corners / Southwest Colorado, the middle half of member counties see their last 28°F hard freeze between May 2 and May 11 (median May 6), and their first fall freeze between Oct 8 and Oct 16. Those are hard freezes, not the last light frost: tender transplants wait for about May 27, and elevation decides which end of a 9-day spread you garden in.
What grows well in the Four Corners / Southwest Colorado?
The Four Corners / Southwest Colorado's conditions suit plants such as Tomato, Colorado Blue Spruce, Apple, Raspberry, Hops, Peach. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is the Four Corners / Southwest Colorado defined?
The Four Corners / Southwest Colorado is defined here as a curated cluster of 4 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does the Four Corners / Southwest Colorado cover?
The Four Corners / Southwest Colorado spans Colorado. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
High Plains, Colorado High Country (Central Rockies), Front Range, San Luis Valley, Arkansas River Valley (Rocky Ford–Pueblo Corridor), and Uncompahgre Valley share at least one state with the Four Corners / Southwest Colorado. Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at the Four Corners / Southwest Colorado’s own scale
6 of the readings below were taken at the Four Corners / Southwest Colorado's own scale — the zone 6a-6b band across its footprint, a median 158-day season across its 4 counties and 1,029 documented federal contamination records across its 4 counties, 486 of them in La Plata County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 6a-6b aggregated across all 4 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 4 counties this region is curated fromGrowable Ground subregion registry
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 4 counties run 149 to 167 frost-free days, median 158NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 1,029 documented federal contamination records across its 4 counties, 486 of them in La Plata County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 37% Alfisols, topsoil pH 5.5–7.8, area-weighted across its 4 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 6a-6bfrom Colorado
What this page can’t tell you
- Which end of the 18-day range your ground sits at — 149 days at one extreme, 167 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore the Four Corners / Southwest Colorado
State growing guides
Counties in this region
Other growing regions across Colorado
A semi-arid shortgrass tableland of deep soils and big sky, where wind, low rainfall, and irrigation shape dryland wheat, sorghum, and resilient gardens.
Colorado's highest gardens sit at 7,500–10,000+ feet, where frost can land in any month and the honest growing window runs 85–141 days across the region's counties — a span a single county figure hides at both ends. Because county centroids average the alpine slopes upward, the committed town data runs colder than the county page: Crested Butte gardens at zone 3b, Gunnison at 4a, Leadville sees roughly 84 frost-free days. This is the short-season opposite pole of the San Luis high-desert basin, and a completely different regime from the Front Range (169 frost-free days) or the Grand Valley (209) — season extension, cold-hardy varieties, and month-round frost vigilance drive every planting decision here.
Colorado's high, dry urban corridor at the foot of the Rockies — intense sun, alkaline soils, and a short season that rewards cold-hardy, drought-wise gardening.
The San Luis Valley is Colorado's high, cold intermountain basin — short frost-free seasons and hard winters — yet Rio Grande irrigation makes it one of the state's most important farming areas, famous for potatoes and barley.
Colorado's irrigated warm-season pocket. The lower Arkansas River bottomland east of the mountains runs a 178-to-191-frost-free-day season in zones 5b-6a — long and warm enough that Rocky Ford built a cantaloupe-and-watermelon reputation and Pueblo its green chile. That specialty-crop identity is nothing like the dryland shortgrass wheat and sorghum of the surrounding High Plains; what sets a parcel apart here is water. The ditch-irrigated valley floor grows heat-loving melons and chiles the unwatered tableland just above it cannot.
The Uncompahgre River valley floor from Montrose past Olathe down to Delta, where Bureau of Reclamation irrigation and a warm 6a-to-7a valley climate stretch the frost-free season from about 130 days upvalley near Montrose to 189 days near Delta.