Allen County, in Kansas, sits in USDA hardiness zone 6b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Crops well matched to these conditions include cabbage, hazelnut, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Allen County holds more than one microclimate.
Soils and elevations shift across Allen County, so your frost dates and drainage aren't the county average. 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 Allen County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Allen County — the short answer
Allen County, Kansas: USDA zone 6b, about 223 days between hard freezes, across 320K acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 29
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 7
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~223
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 320K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 6b is Allen County's average, not your lot's — a low corner or a tree line moves it. Against Allen County's 223-day season, see what your own ground reads.
Heat in Allen County
Across a year, Allen County accumulates about 3,951 growing degree days above 50°F, about 118 more than the middle Kansas county — ahead of 72 of Kansas’s 105 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Allen County
Across Allen County, the ground is predominantly Mollisols, where Kenoma, Wagstaff, and Zaar are the most extensive named soil series. The soil is generally moderately well drained with a silt loam surface. Topsoil pH runs about 5.9–6.4, slightly acidic. Rainfall drains through hydrologic group D soils.
Soil order
Mollisols
Drainage
Moderately well drained
Prime farmland
85%
Hydric soils
3%
Soil still varies lot by lot — soil types explained.
How the ground varies across Allen County
The USDA soil survey maps 46% of Allen County as moderately well drained — but another 53% drains differently: 30% somewhat poorly drained, 20% well drained.
Kenoma is the most extensive named soil at 24% of mapped acres, then Wagstaff (16%) and Zaar (11%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Allen County
Each reading below is measured for Allen County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Allen County are moderately well drained, in hydrologic group D — roughly the middle of the drainage range.
This is close to the middle most vegetables prefer: it holds enough water to carry a crop between rains without staying waterlogged. The catch is that a wet spring or a low corner can still tip it soggy.
Plant on the site as-is for most crops, but keep the lowest, slowest-draining beds for moisture-tolerant plantings.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Allen County runs about pH 5.9–6.4, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredAllen County runs about 223 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredAllen County sits in USDA hardiness zone 6b.
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 Allen County is in
Allen County sits in the Central Irregular Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Allen County
We scored all 1,086 plants against Allen County's own USDA zone 6b and its own 223-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Kansas profile.
Is it too late to plant in Allen County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 29 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 7 — long-season crops need about 90 days of runway, quick greens only 30. With a season this long, “too late” mostly means “switch crops” — second sowings and a full fall garden are the norm, with garlic closing the year.
Documented around Allen County
- monarch butterfly482 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Allen County
USGS estimates 102,087 lb of Glyphosate on Allen County farmland in 2019, its largest by weight, ahead of Acephate (63,132 lb) and Atrazine (28,674 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Allen County — and how to grow with it.
We checked the federal record across Allen County — 172 documented sites across 6 of the 9 source types we track.
The most significant on record: 3 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Allen County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Allen County
Closest first, across Allen County. Listing isn't leaking, and distance isn't exposure.
- 24S 20E 31CCD 01Nitrate · 2.6 mi
- CROWELL'S ONE STOPUnderground Storage Tanks · 2.6 mi
- DOUBLE E TRUCKINGBrownfields · 2.8 mi
- COBERLY RECYCLING (CLOSED)Underground Storage Tanks · 2.9 mi
- GAS BODY SHOPBrownfields · 3.4 mi
- GAS CITY, CITY OFPFAS · 3.6 mi
- CONCRETO SMELTERSuperfund · 4.0 mi
- 25S 19E 06CCB 01Nitrate · 4.3 mi
- 25S 19E 06CBB 02Nitrate · 4.3 mi
- ALLEN CO. AIRPORTUnderground Storage Tanks · 4.5 mi
- 26S 19E 01ABB 01Nitrate · 4.6 mi
- 25S 20E 10CCB 01Nitrate · 4.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Allen County'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 Allen County.
Sources Checked
across Allen County
Severity Distribution
across Allen County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Allen County, two things run higher than the national average across Allen County — PFAS (3 sites) and Nitrate (80 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Allen County
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 Allen County average
Your land is one point inside Allen County
Everything above resolves to Allen County as a whole — one PHZM band and one county frost record, read across 320K 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 county 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 county average.
Your Lot vs the Allen County Average
Allen County Average
- ●USDA Zones 6b, averaged across Allen County
- ●One soil character for all of Allen County
- ●Frost dates read at Allen County's scale: Mar 29 to Nov 7
YOUR Parcel
- ✓Your exact zone, not Allen County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Allen County
Pull a site-specific report for your exact address in Allen County, Kansas — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Allen County averages can't show:
We read public map data around Allen County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Allen County average
How we know this about Allen County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Allen County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Allen County
When does frost risk typically end in Allen County?
The last hard freeze (28°F) in Allen County typically lands around Mar 29, 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 Apr 19.
How long is the growing season in Allen County?
Measured between 28°F hard freezes, Allen County sees about 223 frost-free days — roughly Mar 29 through Nov 7, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 19 to Oct 24, about 188 days.
Is the soil safe to grow vegetables in Allen County?
The federal record around Allen County is a meaningful one — 172 documented sites, mostly Nitrate entries (80), the nearest Nitrate record about 2.6 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.
Everything above is measured at Allen County's scale — its 6b band and its 223-day season. Your yard writes its own version of Allen County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Kansas's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Allen County’s own scale
9 of the readings below were taken at Allen County's own scale — its own ~223-day span between 28°F freezes, the 3 most extensive soil series mapped here and 172 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Allen County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Allen County's own 28°F hard-freeze dates and its ~223-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Allen CountyUSDA NRCS SSURGO
- 172 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 2.6 miles outFederal environmental registers
- Allen County's boundary and the 320,190 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~223-day seasonGrowable Ground crop-matching engine
- Allen County sitting wholly inside the Central Irregular PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Allen County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Allen County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Kansas grower plans around — written at state scale, so they stay on the state guidefrom Kansas
What this page can’t tell you
- How the season shifts across Allen County — the ~223 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Allen County's 320,190 acreswhy one lot differs from the next →
- Which of those 172 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Allen Countyread your own land →