Colorado spans USDA hardiness zones 3b-7b, with a growing season of about 155 frost-free days — room for most garden staples, with a calendar tight enough that frost dates still call the shots.
Its growing climate is shaped by 7-20 inches of annual rainfall, a median of roughly 2,083 growing-degree days (base 50°F), and about 2,500 winter chill hours for tree fruit, which together set what ripens and what struggles. The dominant soils run to sandy loam, clay loam, alkaline caliche, and decomposed granite, and their drainage is one of the strongest predictors of which crops take hold and which falter. Colorado is not one growing region but several — from High Plains, Colorado High Country (Central Rockies), and Front Range — each with its own zone band and frost timing. Crops well matched to these conditions include colorado blue spruce, tomato, penstemon, and apple — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Grounded inUSDA PHZM•NOAA Climate Normals•USDA NRCS SSURGO•GDD (PRISM 1991-2020 normals)•Chill hours (PRISM 1991-2020 normals)•USDA hardiness sub-region map•EPA FRS•USDA PLANTS•Growable Ground suitability scoring
Colorado spans zones 3b-7b, but your yard 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 — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Distinct growing regions within Colorado — each has its own zones, soils, and signature crops.
Colorado: USDA zones 3b-7b, 85–209 frost-free days depending on the county, 64 counties.
The middle half of this state’s counties. Tender transplants usually wait 2–3 weeks past the last hard freeze. The shortest-season figure is Colorado's own county record — Chaffee County's measured 28°F normal, not a modeled floor.
Colorado does not have one growing season. Across all 472 of its towns that carry their own 30-year record, the shortest measured season is Copper Mountain's at 79 days and the longest is Fruitvale's at 215 — a 136-day spread inside one state.
Neither end is a lone reading — another 7 towns measure within 10 days of Copper Mountain and 2 sit within 10 days of Fruitvale. These are real pockets, so the number to plant against is your own town's, not the state average.
NOAA Regional Climate Centers ACIS (1991–2020), 30-year daily minimum record
Zone 3b-7b is Colorado's average, not your lot's — a low corner or a tree line moves it. Against Colorado's 155-day season, see what your own ground reads.
One answer for Colorado averages 64 counties whose growing seasons are 124 days apart — from 85 frost-free days in Chaffee County to 209 in Mesa County. That is the same state, measured the same way, in the same years. Which end of it your county sits nearer decides what finishes before the first hard freeze.
The middle half of 64 counties runs 132–174 days, with a median of 150 days — a 124-day span end to end.
Measured across 64 counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze. A county with no record of its own is absent from the range rather than counted as zero — nothing here is interpolated to the state. Your own site sits somewhere inside this range; a parcel report resolves where.
The middle half of Colorado runs 132–174 frost-free days, and 31 of its 64 counties sit outside that — 15 on the short side, 16 on the long. A statewide planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 132 frost-free days
15 counties
3 of 15 shown
The end of the state that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
132–174 frost-free days
33 counties
0 of 33 shown
The middle half of the state, and the part a single statewide date describes well.
Over 174 frost-free days
16 counties
3 of 16 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, county 28°F killing freeze), the same figure its own guide page publishes. Elevation, slope and cold-air drainage move a yard within its county as well — which is the part only your address resolves.
The soil types that dominate Colorado — how each drains decides more about crop success than almost anything else. Tap any soil to learn what it is and how to work with it. Each photo is a representative profile of that soil type; the named series is where it was documented, which is often another state.
Drainage
Fast. The sand fraction opens the soil up, so water moves through the root zone quickly and the surface rarely stays soggy. The trade is that nutrients ride out with the water.
What thrives
Root crops love it — carrots, potatoes, radishes, and onions size up cleanly in ground they can push through. Melons, sweet potatoes, asparagus, and most herbs appreciate the warmth and the drainage.
Loam tilted toward clay — heavier in the hand, slower to dry, and richer in nutrients than its sandier cousins. Clay particles carry a surface charge that holds fertilizer and minerals where roots can reach them.
Drainage
Slow to moderate. Water lingers in the root zone longer than in loam, which is a gift in dry summers and a challenge in wet springs.
What thrives
Heavy feeders that appreciate steady moisture — brassicas, corn, beans, and many fruit trees. Perennials with strong root systems establish well once they are through the first season.
Drainage
The layer itself is nearly waterproof: water perches on top of it, and roots stop where it starts unless it is broken.
What thrives
Desert natives handle caliche country naturally — mesquite, desert willow, agave, and wildflowers. Vegetables and fruit trees succeed where planting holes punch through the layer or beds rise above it.
Drainage
Very fast. Water moves through the gritty matrix almost immediately, and nutrients follow.
What thrives
Plants that demand sharp drainage love it: lavender, rosemary, salvias, California natives, succulents, and wine grapes on hillside sites.
Drainage
Usually good: rivers sort their loads, and most alluvial soils have enough sand and silt to move water while holding plenty for roots. Low-lying pockets can run wet.
What thrives
Nearly everything — vegetables, orchards, vines, and berries all prosper on alluvium. Its depth lets roots go as far down as they care to.
Soil data: USDA NRCS SSURGO · Soil types explained
Plants well-suited to Colorado's climate, soils, and growing season — each links to its full growing profile.
For most of the year, no — what changes is which crops still fit the days remaining. Across Colorado, cool-season planting typically opens about four weeks before the local last hard freeze — county medians put that freeze near May 6, with the middle half of counties between Apr 25 and May 19 (NOAA 1991–2020 climate normals). Tender transplants wait two to three weeks past it, and fall planting counts back from first freezes mostly between Sep 29 and Oct 16 — 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.
The plants Colorado put its name on — cultural emblems, not growing recommendations.
Colorado blue columbine
Aquilegia coerulea
Designated 1899.
Picea pungens
Designated 1939. In our plant library — see its full growing profile.
Plants the USDA PLANTS Database documents as native and present in Colorado — a real per-state range, not just a zone match. Ordered by how closely each plant’s published hardiness range matches Colorado’s zones 3b-7b, so this is a shortlist by climate fit, not a ranking of which plants matter most here. Presence is statewide, so a plant may still be uncommon in your specific county; your state’s Cooperative Extension or a native-plant society is the local authority.
US-native plants whose hardiness range overlaps Colorado’s USDA zones 3b-7b but which USDA PLANTS doesn’t map to a single state range here. Zone overlap is a starting filter, not a range map.
What an experienced grower plans around here — each one has a move.
Low annual rainfall (7-20 inches) means irrigation is essential nearly everywhere
Build the irrigation first — drip plus mulch makes a high-desert garden run on remarkably little water.
High altitude UV and temperature swings stress plants
Harden transplants gradually, shade-cloth their first high-sun week, and keep row covers handy for cold nights.
Very short growing season at elevation (60-90 frost-free days above 8,000 ft)
Above 8,000 feet, count your real frost-free days and choose varieties bred to finish inside them.
Alkaline soils (pH 7.5-8.5) limit acid-loving plants without amendment
A soil test tells you your actual pH — grow acid-lovers in containers of amended mix while the native ground grows everything else.
For cultivar selection, pest pressure, and planting-time guidance specific to Colorado, the Colorado State University Extension is the authoritative local source.
Safe to Grow Here?What the federal record shows across Colorado — and how to grow with it.
We checked the federal record across Colorado — 29,759 documented sites across 8 of the 9 source types we track.
The most significant on record: 281 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Colorado 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.
Severity Distribution
across Colorado
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Colorado, Mining runs higher than the national average — 5,049 sites across Colorado. 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.
Everything above resolves to Colorado as a whole — a state whose own counties record seasons 124 days apart, and hardiness across zones 3b-7b. 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 state 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 statewide average.
State averages sketch the shape. Your soil, sun exposure, drainage, and microclimate decide what actually takes. Pull a site-specific report for your exact parcel.
Enter your address. We read your soil, sun, drainage, and frost dates, then score 1,086 plants against the real conditions on your land.
Three things about your lot that Colorado averages can't show:
We read public map data around Colorado — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Colorado average
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read per county and aggregated to the state band; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each county’s own record; rainfall from NOAA Climate Normals; soils from USDA NRCS SSURGO; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above. Where a county carries no record of its own, it is absent from the figure rather than filled in.
Colorado spans USDA hardiness zones 3b-7b — which is to say winter's coldest night runs from about −35°F to 10°F depending where in Colorado you are, averaged over 1991–2020 (USDA PHZM 2023).
For most of the year, no — what changes is which crops still fit the days remaining. Across Colorado, cool-season planting typically opens about four weeks before the local last hard freeze — county medians put that freeze near May 6, with the middle half of counties between Apr 25 and May 19 (NOAA 1991–2020 climate normals). Tender transplants wait two to three weeks past it, and fall planting counts back from first freezes mostly between Sep 29 and Oct 16 — 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.
Across Colorado, the middle half of counties see their last hard freeze (28°F) between about Apr 25 and May 19, with a county median near May 6 (NOAA 1991–2020 climate normals). 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 27.
Measured between 28°F hard freezes, growing seasons across Colorado's counties mostly run about 134 to 175 days, with a county median near 155 (NOAA 1991–2020 climate normals). Tender crops get a somewhat shorter practical window, since lighter frosts reach a few weeks past the hard-freeze dates on both ends.
Colorado's zones 3b-7b support a wide range — strong performers include Colorado Blue Spruce, Tomato, Penstemon, Apple, and Peach. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Officially, Colorado spans USDA zones 3b-7b (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,086 plants against what's actually there.
The federal record across Colorado runs heavier than most — 29,759 documented sites, mostly Underground Storage Tanks entries (11,290) — 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.
Start with three facts. Colorado spans USDA zones 3b-7b, which sets what survives winter; last hard freezes range from about Apr 25 to May 19 across its counties (NOAA 1991–2020 climate normals); and 29,759 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything above is measured at Colorado's scale — its 3b-7b band and its 155-day season. Your yard writes its own version of Colorado's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
6 of the readings below were taken at Colorado's own scale — the full zone 3b-7b span inside its borders, the 5 soil types that dominate its ground and 29,759 documented sites on its federal record; anything it cannot resolve at this scale is named below.
Measured here
What this page can’t tell you
Explore growing conditions by county — each has its own zone range and land area.
Explore growing conditions by city or town in Colorado.
