Kirwin, Kansas, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Reliable performers under these conditions include cabbage, hazelnut, lavender, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Even in Kirwin, 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 Kirwin 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 Kirwin — soil, climate, flood, and parcel records. How we handle your address.
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Kirwin — the short answer
Kirwin, Kansas: USDA zone 6a, about 187 days between hard freezes, across 586 acres of city.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 15
- 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
- ~187
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 586 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 Kirwin's average, not your lot's — a low corner or a tree line moves it. Against Kirwin's 187-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Kirwin
Each reading below is measured for Kirwin itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredKirwin runs about 187 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
MeasuredKirwin 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 Kirwin is in
Kirwin sits in the Central Great Plains — EPA Level III, inside the wider Great Plains. That is read at Kirwin's own centroid rather than borrowed from Phillips County.
What Grows in Kirwin
Every plant below cleared Kirwin's own zone 6a and its 187-day season. Each card opens that plant's Kansas profile. How we score.
Is it too late to plant in Kirwin?
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 18; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 15 (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. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Kirwin
Closest first, within ~10 miles of Kirwin. Listing isn't leaking, and distance isn't exposure.
- 04S 16W 27CCA 01Nitrate · 1100 ft
- KIRWIN DAM OUTLETBrownfields · 1200 ft
- I M T C INCBrownfields · 1300 ft
- BUREAU OF RECLAMATIONUnderground Storage Tanks · 2300 ft
- WYRILL FARMING INCUnderground Storage Tanks · 1.0 mi
- 05S 16W 03BC 01Nitrate · 1.4 mi
- DANE G. HANSEN SCOUT RESERVASIUnderground Storage Tanks · 1.5 mi
- WYRILL FARMING INCBrownfields · 1.5 mi
- 04S 16W 20DA 01Nitrate · 1.8 mi
- 04S 16W 26DA 01Nitrate · 1.9 mi
- 04S 16W 30CC 01Nitrate · 2.9 mi
- NORDEN, DONALDUnderground Storage Tanks · 3.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Kirwin'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 Kirwin.
Total Sites
55
within ~10 miles of Kirwin
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Kirwin
Severity Distribution
within ~10 miles of Kirwin
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Kirwin, Nitrate runs higher than the national average — 32 sites within ~10 miles of Kirwin. 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 Kirwin
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 Kirwin average
Your land is one point inside Kirwin
Everything above resolves to Kirwin as a whole — one PHZM band and one 28°F frost record, read across 586 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 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 Kirwin Average
Kirwin Average
- ●USDA Zones 6a, averaged across Kirwin
- ●One soil character for all of Kirwin
- ●Frost dates read at Kirwin's scale: Apr 15 to Oct 19
YOUR Parcel
- ✓Your exact zone, not Kirwin's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Kirwin
Pull a site-specific report for your exact address in Kirwin, Kansas — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Kirwin averages can't show:
We read public map data around Kirwin — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Kirwin average
How we know this about Kirwin
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 Kirwin’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 Kirwin
When does frost risk typically end in Kirwin?
The last hard freeze (28°F) in Kirwin typically lands around Apr 15, 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 6.
When is the first frost in Kirwin?
The first hard freeze (28°F) in Kirwin 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 187 days after the spring freeze cleared.
How long is the growing season in Kirwin?
Measured between 28°F hard freezes, Kirwin sees about 187 frost-free days — roughly Apr 15 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 6 to Oct 5, about 152 days.
Is the soil safe to grow vegetables in Kirwin?
The federal record around Kirwin is a meaningful one — 55 documented sites, mostly Nitrate entries (32), 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 Kirwin?
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 Kirwin's scale — its 6a band and its 187-day season. Your yard writes its own version of Kirwin'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 Kirwin’s own scale
6 of the readings below were taken at Kirwin's own scale — its own ~187-day season between 28°F freezes, the 586 acres it covers and 55 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Kirwin's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Kirwin's own 28°F hard-freeze dates, about Apr 15 and Oct 19 and the ~187-day span between themNOAA 1991–2020 Climate Normals
- 55 documented contamination sites on the federal record near Kirwin, the closest Nitrate record about 0.2 miles out from the town centreFederal environmental registers
- Kirwin's boundary and the 586 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~187-day seasonGrowable Ground crop-matching engine
- The ecoregion at Kirwin's own centroid, the Central Great PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Kirwin's 586 acres read through its county's SSURGO summaryfrom Phillips County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Phillips County
- The growing challenges every Kansas grower plans around — written at state scale, so they stay on the state guidefrom Kansas
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Phillips County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Kirwin's 586 acreswhy one lot differs from the next →
- Which side of Kirwin you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 586 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 Kirwin-wide figureread your own land →
More in Kansas
Wider growing context
What grows across KansasKirwin sits outside our named growing regions, so Kansas as a whole is its closest context here.
Nearby growing guides