The Colorado High Country (Central Rockies) spans USDA hardiness zones 4b-6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
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. Expect colorado blue spruce, tomato, apple, and raspberry to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
The Colorado High Country (Central Rockies) spans Colorado.
Your yard isn't all of the Colorado High Country (Central Rockies).
The Colorado High Country (Central Rockies) spans USDA zones 4b-6a, 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 Colorado High Country (Central Rockies) — soil, climate, flood, and parcel records. How we handle your address.
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The Colorado High Country (Central Rockies) — the short answer
The Colorado High Country (Central Rockies): USDA zones 4b-6a, 85–141 frost-free days depending where in it you stand, in Colorado.
- USDA zones
- 4b-6a
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 85 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Chaffee County
- Counties
- 16
- 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. The season figure is this region's own record, measured across its 16 member counties, not a state or national average.
Hardiness Zone Range
The Colorado High Country (Central Rockies) is not one growing season
One answer for the Colorado High Country (Central Rockies) averages 16 counties whose growing seasons are 56 days apart — from 85 frost-free days in Chaffee County to 141 in Eagle County. That is the same region, measured the same way, in the same years. Which end of it your land sits nearer decides what finishes before the first hard freeze.
The middle half of 16 counties runs 101–133 days, with a median of 109 days — a 56-day span end to end.
Measured across 16 member counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020. A member with no own record is absent from the range rather than counted as zero — nothing here is interpolated to the region. Your own site sits somewhere inside this range; a parcel report resolves where.
Where the line runs inside the Colorado High Country (Central Rockies)
The middle half of the Colorado High Country (Central Rockies) runs 101–133 frost-free days, and 8 of its 16 counties sit outside that — 4 on the short side, 4 on the long. A regional planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 101 frost-free days
4 counties
- Chaffee County · 85 days
- Hinsdale County · 97 days
- Lake County · 97 days
3 of 4 shown
The end of the region that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
101–133 frost-free days
8 counties
0 of 8 shown
The middle half of the region, and the part a single regional season describes well.
Over 133 frost-free days
4 counties
- Eagle County · 141 days
- Custer County · 139 days
- Routt County · 135 days
3 of 4 shown
Long enough for a second succession of a quick crop after the first comes out.
Each county is placed by its OWN 28°F frost-free normal (NOAA Regional Climate Centers ACIS, 1991-2020), the same figure its own guide page publishes. Elevation, slope and cold-air drainage move a site within its county as well — which is the part only your address resolves.
What Grows in the Colorado High Country (Central Rockies)
All 1 of the plants below that publish a season requirement clear even Chaffee County’s 85 frost-free days — so on season alone, this grid works at both ends of the region. The 56-day spread still decides how far past this list you can push, and how early you can start.
Plants matched to the Colorado High Country (Central Rockies)'s USDA zones 4b-6a, 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 Colorado High Country (Central Rockies)
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Colorado High Country (Central Rockies)’s USDA zones 4b-6a — 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 Colorado High Country (Central Rockies)
The USDA soil survey maps this ground county by county. These are those records weighted by land area across 16 member counties — this region’s own profile, not a state figure.
The ground is predominantly Mollisols, at 51% of mapped acres, followed by Alfisols (18%), Inceptisols (14%) and Entisols (10%). Eight 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 Leighcan, Dominson, and Bushpark.
75% of those acres are well drained, and another 9% somewhat excessively drained, 3% poorly drained. Topsoil pH runs 5.6–7.9 between the lowest and the highest county on record.
Soil order
Mollisols
Drainage
Well drained
Topsoil pH
5.6–7.9
Hydric soils
5%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Chaffee County holds the most wetland ground here, at 11% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Colorado High Country (Central Rockies)
The soil survey reads this ground county by county, and the readings above are those records summed across the Colorado High Country (Central Rockies). Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records75% of the mapped acres across the Colorado High Country (Central Rockies) are well drained — ground that drains quickly. That is area-weighted across all 16 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 Colorado High Country (Central Rockies) runs pH 5.6–7.9 — near neutral in 13 of its 16 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 Colorado High Country (Central Rockies) — and how to grow with it.
Across the Colorado High Country (Central Rockies)'s 16 counties the federal record holds 5,865 documented sites, mostly Mining (3,333), Nitrate (1,078) and Underground Storage Tanks (1,054). The heaviest single county is Park County, with 771.
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 Colorado High Country (Central Rockies) to see which records sit where you actually grow.
Sources Checked
Summed across the 16 counties in the Colorado High Country (Central Rockies)
A note from Gnorman
What an experienced grower watches for around here
In and around the Colorado High Country (Central Rockies), Mining runs higher than the national average — 3,333 sites across the 16 counties in the Colorado High Country (Central Rockies). 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.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Colorado High Country (Central Rockies)
Everything above resolves to the Colorado High Country (Central Rockies) as a whole — a footprint whose own counties record seasons 56 days apart, and hardiness across zones 4b-6a. Your parcel sits at one point in that range, not in the middle of it. 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 Colorado High Country (Central Rockies) Average
Colorado High Country (Central Rockies) Average
- ●USDA Zones 4b-6a, averaged across Colorado High Country (Central Rockies)
- ●One soil character for all of Colorado High Country (Central Rockies)
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Colorado High Country (Central Rockies)'s 4b-6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Colorado High Country (Central Rockies)
Pull a site-specific report for your exact address in the Colorado High Country (Central Rockies) — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Colorado High Country (Central Rockies) averages can't show:
We read public map data around The Colorado High Country (Central Rockies) — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Colorado High Country (Central Rockies) average
How we know this about the Colorado High Country (Central Rockies)
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 Colorado High Country (Central Rockies)
What hardiness zone is the Colorado High Country (Central Rockies)?
The Colorado High Country (Central Rockies) spans USDA hardiness zones 4b-6a, 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 Colorado High Country (Central Rockies)?
Measured between 28°F hard freezes, the Colorado High Country (Central Rockies)'s counties mostly run 101 to 133 frost-free days, median 109 (NOAA Regional Climate Centers ACIS, 1991–2020, over 16 member counties). That 32-day spread is the honest read — no single season describes 16 counties, and each county guide below carries its own.
When does frost risk end in the Colorado High Country (Central Rockies)?
Across the Colorado High Country (Central Rockies), the middle half of member counties see their last 28°F hard freeze between May 20 and Jun 6 (median May 31), and their first fall freeze between Sep 16 and Sep 29. Those are hard freezes, not the last light frost: tender transplants wait for about Jun 21, and elevation decides which end of a 17-day spread you garden in.
What grows well in the Colorado High Country (Central Rockies)?
The Colorado High Country (Central Rockies)'s conditions suit plants such as Colorado Blue Spruce, Tomato, Apple, Raspberry, Hops, Chokecherry. 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 Colorado High Country (Central Rockies) defined?
The Colorado High Country (Central Rockies) is defined here as a curated cluster of 16 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 Colorado High Country (Central Rockies) cover?
The Colorado High Country (Central Rockies) spans Colorado. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
High Plains, Front Range, San Luis Valley, Arkansas River Valley (Rocky Ford–Pueblo Corridor), Four Corners / Southwest Colorado, and Uncompahgre Valley share at least one state with the Colorado High Country (Central Rockies). 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 Colorado High Country (Central Rockies)’s own scale
6 of the readings below were taken at the Colorado High Country (Central Rockies)'s own scale — the zone 4b-6a band across its footprint, a median 109-day season across its 16 counties and 5,865 documented federal contamination records across its 16 counties, 771 of them in Park County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 4b-6a aggregated across all 16 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 16 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 16 counties run 101 to 133 frost-free days, median 109NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 5,865 documented federal contamination records across its 16 counties, 771 of them in Park County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 51% Mollisols, topsoil pH 5.6–7.9, area-weighted across its 16 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 4b-6afrom Colorado
What this page can’t tell you
- Which end of the 32-day range your ground sits at — 101 days at one extreme, 133 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 Colorado High Country (Central Rockies)
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 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.
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").
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.