Holly Hills, Colorado, sits in USDA hardiness zone 6a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Crops well matched to these conditions include cabbage, blackberry, california poppy, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Holly Hills, 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 Holly Hills 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 Holly Hills — soil, climate, flood, and parcel records. How we handle your address.
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Holly Hills — the short answer
Holly Hills, Colorado: USDA zone 6a, about 180 days between hard freezes, across 371 acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~180
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 371 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 Holly Hills's average, not your lot's — a low corner or a tree line moves it. Against Holly Hills's 180-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Holly Hills
Each reading below is measured for Holly Hills itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredHolly Hills runs about 180 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
MeasuredHolly Hills 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 Holly Hills is in
Holly Hills sits in the High Plains — EPA Level III, inside the wider Great Plains. That is read at Holly Hills's own centroid rather than borrowed from Denver County.
What Grows in Holly Hills
Every plant below cleared Holly Hills's own zone 6a and its 180-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Holly Hills?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 25; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 22 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 19 — 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.
What's on the federal record near Holly Hills
Closest first, within ~10 miles of Holly Hills. Listing isn't leaking, and distance isn't exposure.
- ASPEN SIESTABrownfields · 950 ft
- Diamond Shamrock 1101Underground Storage Tanks · 1200 ft
- Diamond Shamrock 4081Underground Storage Tanks · 1500 ft
- Olmsteads Southeast TexacoUnderground Storage Tanks · 1800 ft
- SAFEWAY STORE #1267Brownfields · 2100 ft
- SILVER STATE CLEANERSBrownfields · 2100 ft
- Monaco Plaza 66Underground Storage Tanks · 2400 ft
- Sinclair 5029Underground Storage Tanks · 2600 ft
- HOLLY HEIGHTS NURSING CENTERBrownfields · 0.5 mi
- HIGHLINE REHABILITATION AND CARE COMMUNITYBrownfields · 0.5 mi
- Bradley Elementary SchoolUnderground Storage Tanks · 0.5 mi
- Econo Lube N TuneUnderground Storage Tanks · 0.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Holly Hills'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 Holly Hills.
Sources Checked
within ~10 miles of Holly Hills
Severity Distribution
within ~10 miles of Holly Hills
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Holly Hills
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 Holly Hills average
Your land is one point inside Holly Hills
Everything above resolves to Holly Hills as a whole — one PHZM band and one 28°F frost record, read across 371 acres. Your parcel is one point inside that footprint. 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 town 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 Holly Hills Average
Holly Hills Average
- ●USDA Zones 6a, averaged across Holly Hills
- ●One soil character for all of Holly Hills
- ●Frost dates read at Holly Hills's scale: Apr 22 to Oct 19
YOUR Parcel
- ✓Your exact zone, not Holly Hills's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Holly Hills
Pull a site-specific report for your exact address in Holly Hills, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Holly Hills averages can't show:
We read public map data around Holly Hills — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Holly Hills average
How we know this about Holly Hills
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Holly Hills’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 town grain anywhere on this page — there is no town-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 Holly Hills
When does frost risk typically end in Holly Hills?
The last hard freeze (28°F) in Holly Hills typically lands around Apr 22, 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 13.
When is the first frost in Holly Hills?
The first hard freeze (28°F) in Holly Hills typically arrives around Oct 19, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 5, so the watching starts about Sep 19 — about 180 days after the spring freeze cleared.
How long is the growing season in Holly Hills?
Measured between 28°F hard freezes, Holly Hills sees about 180 frost-free days — roughly Apr 22 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 13 to Oct 5, about 145 days.
Is the soil safe to grow vegetables in Holly Hills?
The federal record around Holly Hills runs heavier than most — 5,201 documented sites, mostly Underground Storage Tanks entries (2,911), the nearest Brownfields record about 0.2 miles out — 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.
How do I protect my plants from frost in Holly Hills?
From about Sep 19 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 19 (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 19. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Holly Hills's scale — its 6a band and its 180-day season. Your yard writes its own version of Holly Hills'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 Holly Hills’s own scale
6 of the readings below were taken at Holly Hills's own scale — its own ~180-day season between 28°F freezes, the 371 acres it covers and 5,201 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Holly Hills's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Holly Hills's own 28°F hard-freeze dates, about Apr 22 and Oct 19 and the ~180-day span between themNOAA 1991–2020 Climate Normals
- 5,201 documented contamination sites on the federal record near Holly Hills, the closest Brownfields record about 0.2 miles out from the town centreFederal environmental registers
- Holly Hills's boundary and the 371 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~180-day seasonGrowable Ground crop-matching engine
- The ecoregion at Holly Hills's own centroid, the High PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Holly Hills's 371 acres read through its county's SSURGO summaryfrom Denver County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Denver 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 Denver County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Holly Hills's 371 acreswhy one lot differs from the next →
- Which side of Holly Hills you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 371 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields 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 Holly Hills-wide figureread your own land →