Louisville, Colorado, sits in USDA hardiness zone 6a — a zone band wide enough that plant choice, not possibility, is the interesting question.
A short list that earns its place here — cabbage, hazelnut, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Louisville, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Louisville lot. 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 Louisville — soil, climate, flood, and parcel records. How we handle your address.
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Louisville — the short answer
Louisville, Colorado: USDA zone 6a, about 186 days between hard freezes, across 5K acres of city.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 21
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~186
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 5K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 Louisville's average, not your lot's — a low corner or a tree line moves it. Against Louisville's 186-day season, see what your own ground reads.
Your town runs its own season
Louisville's own 30-year record measures about 186 days between 28°F killing freezes — 44 days longer than Boulder County's ~142. Both are measured records, not estimates.
That gap is the whole reason a county average can mislead here. Plant against Louisville's ~186-day season rather than the county figure — and the sun, slope and cold-air drainage on your specific lot move it again.
NOAA Regional Climate Centers ACIS (1991–2020), 30-year daily minimum record. Both figures are measured records — this town’s own and its county’s. A town with no record of its own is absent here rather than estimated.
Soil varies lot by lot — soil types explained.
What this means for growing in Louisville
Each reading below is measured for Louisville itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredLouisville runs about 186 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredLouisville 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 Louisville is in
Louisville sits in the High Plains — EPA Level III, inside the wider Great Plains. That is read at Louisville's own centroid, and it is not what its county reads: Boulder County is mostly Southern Rockies. The wider page above you is answering a different question about different ground.
What Grows in Louisville
Every plant below cleared Louisville's own zone 6a and its 186-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Louisville?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 21; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 18 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 21 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Louisville
Closest first, within ~10 miles of Louisville. Listing isn't leaking, and distance isn't exposure.
- SC00106917BCAD SITE C65Nitrate · 850 ft
- KLT Gas & GroceryUnderground Storage Tanks · 0.8 mi
- Chans Foreign CarsUnderground Storage Tanks · 1.0 mi
- COATING ATOMIZATION TECHNOLOGIESBrownfields · 1.0 mi
- SAFEWAY 2812Brownfields · 1.0 mi
- 7-Eleven #27728Underground Storage Tanks · 1.1 mi
- Clarence M & Jerry CarosellaUnderground Storage Tanks · 1.1 mi
- CENTENNIAL AUTOMOTIVE REPAIRBrownfields · 1.1 mi
- HONEYWELL AEROSPACE US LLCBrownfields · 1.1 mi
- My Goods Market #6529Underground Storage Tanks · 1.1 mi
- COAL CREEK COLLISION CENTERBrownfields · 1.1 mi
- HOME DEPOT STORE #1506Brownfields · 1.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Louisville'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 Louisville.
Sources Checked
within ~10 miles of Louisville
Severity Distribution
within ~10 miles of Louisville
Highest-Severity Sites
Know Before You Grow
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Louisville
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 Louisville average
Your land is one point inside Louisville
Everything above resolves to Louisville as a whole — and this is a city whose own 30-year record already runs a season its county’s does not. Your parcel sits at one point inside even that. 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 city 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 local average.
Your Lot vs the Louisville Average
Louisville Average
- ●USDA Zones 6a, averaged across Louisville
- ●One soil character for all of Louisville
- ●Frost dates read at Louisville's scale: Apr 18 to Oct 21
YOUR Parcel
- ✓Your exact zone, not Louisville's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Louisville
Pull a site-specific report for your exact address in Louisville, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Louisville averages can't show:
We read public map data around Louisville — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Louisville average
How we know this about Louisville
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Louisville’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Louisville
When does frost risk typically end in Louisville?
The last hard freeze (28°F) in Louisville typically lands around Apr 18, 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 May 9.
When is the first frost in Louisville?
The first hard freeze (28°F) in Louisville typically arrives around Oct 21, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 7, so the watching starts about Sep 21 — about 186 days after the spring freeze cleared.
How long is the growing season in Louisville?
Measured between 28°F hard freezes, Louisville sees about 186 frost-free days — roughly Apr 18 through Oct 21, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 9 to Oct 7, about 151 days.
Is the soil safe to grow vegetables in Louisville?
The federal record around Louisville is a meaningful one — 1,183 documented sites, mostly Brownfields entries (505), the nearest Nitrate record about 0.2 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Louisville?
From about Sep 21 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 21 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 21. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Louisville's scale — its 6a band and its 186-day season. Your yard writes its own version of Louisville's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Louisville’s own scale
6 of the readings below were taken at Louisville's own scale — its own ~186-day season between 28°F freezes, the 5,101 acres it covers and 1,183 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Louisville's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Louisville's own 28°F hard-freeze dates, about Apr 18 and Oct 21 and the ~186-day span between themNOAA 1991–2020 Climate Normals
- 1,183 documented contamination sites on the federal record near Louisville, the closest Nitrate record about 0.2 miles out from the town centreFederal environmental registers
- Louisville's boundary and the 5,101 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~186-day seasonGrowable Ground crop-matching engine
- Louisville sits in the High Plains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Louisville's 5,101 acres read through its county's SSURGO summaryfrom Boulder County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Boulder County
- The growing challenges every Colorado grower plans around — written at state scale, so they stay on the state guidefrom Colorado
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Boulder County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Louisville's 5,101 acreswhy one lot differs from the next →
- Which side of Louisville you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 5,101 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.2 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Louisville-wide figureread your own land →
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Growing region
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