Colorado spans USDA hardiness zones 3a-7a, with a growing season of about 190 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 3,500 growing-degree days (base 50°F), and about 1,200 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 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 2023•NOAA Climate Normals•USDA NRCS SSURGO•GDD aggregate (Cornell CALS)•Chill-hour aggregate (MSU Extension)•USDA hardiness sub-region map•EPA FRS•USDA PLANTS•Growable Ground suitability scoring
Colorado spans zones 3a-7a, but your yard sits in exactly one — and slope, tree cover, and low spots nudge it further. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — 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.
USDA Zones
3a-7a
USDA PHZM 2023
Last Frost
Apr 15 - Jun 15
NOAA 30-yr Normals
First Frost
Aug 25 - Oct 15
NOAA 30-yr Normals
Annual Rainfall
7-20 inches
NOAA Climate Normals
Zone maps are averages across Colorado. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
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.
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.
No verified open-license photo yet — this loam is close kin to the loam and silt-loam profiles above.
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 Apr 24, with the middle half of counties between Apr 10 and May 7 (NOAA 1991–2020 climate normals). Tender transplants wait two to three weeks past it, and fall planting counts back from first freezes mostly between Oct 8 and Oct 26 — 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. 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 3a-7a 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 nearby. 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.
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 1,112 plants against the real conditions on your land.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Colorado spans USDA hardiness zones 3a-7a, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
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 Apr 24, with the middle half of counties between Apr 10 and May 7 (NOAA 1991–2020 climate normals). Tender transplants wait two to three weeks past it, and fall planting counts back from first freezes mostly between Oct 8 and Oct 26 — 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 10 and May 7, with a county median near Apr 24 (NOAA 1991–2020 climate normals). That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
Measured between 28°F hard freezes, growing seasons across Colorado's counties mostly run about 154 to 200 days, with a county median near 180 (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 3a-7a 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 3a-7a (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 1,112 plants against what's actually there.
The federal record across Colorado runs heavier than most — 29,759 documented sites — 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 3a-7a, which sets what survives winter; last hard freezes range from about Apr 10 to May 7 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 on this page is a Colorado average. Your yard writes its own version — we read soil, sun, drainage, and frost at your exact address. Try it for 14 days — no card required.
Explore growing conditions by county — each has its own zone range and land area.
Explore growing conditions by city or town in Colorado.
