Calhan, Colorado, sits in USDA hardiness zone 5b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
On paper, cabbage, cranberry, lavender, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Even in Calhan, 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 Calhan 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 Calhan — soil, climate, flood, and parcel records. How we handle your address.
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Calhan — the short answer
Calhan, Colorado: USDA zone 5b, about 157 days between hard freezes, across 582 acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 4
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 8
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~157
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 582 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 5b is Calhan's average, not your lot's — a low corner or a tree line moves it. Against Calhan's 157-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Calhan
Each reading below is measured for Calhan itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCalhan runs about 157 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
MeasuredCalhan sits in USDA hardiness zone 5b.
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 Calhan is in
Calhan sits in the Southwestern Tablelands — EPA Level III, inside the wider Great Plains. That is read at Calhan's own centroid rather than borrowed from El Paso County.
What Grows in Calhan
Every plant below cleared Calhan's own zone 5b and its 157-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Calhan?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Apr 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 8 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
What's on the federal record near Calhan
Closest first, within ~10 miles of Calhan. Listing isn't leaking, and distance isn't exposure.
- D & C ServiceUnderground Storage Tanks · 700 ft
- Warren's GarageUnderground Storage Tanks · 750 ft
- EL PASO COUNTY FACILITIES MANAGEMENTBrownfields · 950 ft
- Calhan Maint FacUnderground Storage Tanks · 1000 ft
- CDOT CalhanUnderground Storage Tanks · 1100 ft
- CALHAN PUBLIC SCHOOLBrownfields · 1100 ft
- Global Leasing Inc - CalhanUnderground Storage Tanks · 1200 ft
- Charles DunganUnderground Storage Tanks · 1300 ft
- Loaf N Jug #50Underground Storage Tanks · 1400 ft
- Ellicott GarageUnderground Storage Tanks · 1800 ft
- 24 Seven GasUnderground Storage Tanks · 1900 ft
- GOLDEN WEST WINDBrownfields · 3.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Calhan'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 Calhan.
Sources Checked
within ~10 miles of Calhan
Severity Distribution
within ~10 miles of Calhan
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Calhan, Nitrate runs higher than the national average — 26 sites within ~10 miles of Calhan. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Calhan
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 Calhan average
Your land is one point inside Calhan
Everything above resolves to Calhan as a whole — one PHZM band and one 28°F frost record, read across 582 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 Calhan Average
Calhan Average
- ●USDA Zones 5b, averaged across Calhan
- ●One soil character for all of Calhan
- ●Frost dates read at Calhan's scale: May 4 to Oct 8
YOUR Parcel
- ✓Your exact zone, not Calhan's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Calhan
Pull a site-specific report for your exact address in Calhan, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Calhan averages can't show:
We read public map data around Calhan — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Calhan average
How we know this about Calhan
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 Calhan’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 Calhan
When does frost risk typically end in Calhan?
The last hard freeze (28°F) in Calhan typically lands around May 4, 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 25.
When is the first frost in Calhan?
The first hard freeze (28°F) in Calhan typically arrives around Oct 8, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 24, so the watching starts about Sep 8 — about 157 days after the spring freeze cleared.
How long is the growing season in Calhan?
Measured between 28°F hard freezes, Calhan sees about 157 frost-free days — roughly May 4 through Oct 8, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 24, about 122 days.
Is the soil safe to grow vegetables in Calhan?
The federal record around Calhan is light — 41 documented sites across the 9 federal source types we checked, mostly Nitrate entries (26), the nearest Underground Storage Tanks record about 0.1 miles out — and proximity to a documented site is information, not a diagnosis of any one yard. Growing food here starts from a strong position; a soil test before new food beds settles any site-specific question.
How do I protect my plants from frost in Calhan?
From about Sep 8 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 8 (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 8. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Calhan's scale — its 5b band and its 157-day season. Your yard writes its own version of Calhan'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 Calhan’s own scale
6 of the readings below were taken at Calhan's own scale — its own ~157-day season between 28°F freezes, the 582 acres it covers and 41 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Calhan's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Calhan's own 28°F hard-freeze dates, about May 4 and Oct 8 and the ~157-day span between themNOAA 1991–2020 Climate Normals
- 41 documented contamination sites on the federal record near Calhan, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- Calhan's boundary and the 582 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~157-day seasonGrowable Ground crop-matching engine
- The ecoregion at Calhan's own centroid, the Southwestern TablelandsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Calhan's 582 acres read through its county's SSURGO summaryfrom El Paso County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom El Paso 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 El Paso County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Calhan's 582 acreswhy one lot differs from the next →
- Which side of Calhan you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 582 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 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 Calhan-wide figureread your own land →
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