Riley County, in Kansas, sits in USDA hardiness zone 6b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Growers here do well with cabbage, hazelnut, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Riley County lies within the Flint Hills — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Riley County holds more than one microclimate.
Soils and elevations shift across Riley 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 Riley County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Riley County — the short answer
Riley County, Kansas: USDA zone 6b, about 205 days between hard freezes, across 390K acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 6
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 28
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~205
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 390K 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 Riley County's average, not your lot's — a low corner or a tree line moves it. Against Riley County's 205-day season, see what your own ground reads.
Heat in Riley County
Across a year, Riley County accumulates about 3,808 growing degree days above 50°F, about 25 fewer than the middle Kansas county — ahead of 49 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 Riley County
Across Riley County, the ground is predominantly Mollisols, where Clime, Wymore, and Irwin are the most extensive named soil series. The soil is generally well drained with a silty clay loam surface. Topsoil pH runs about 6.0–7.5, neutral. Rainfall drains through hydrologic group D soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
40%
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Riley County
The USDA soil survey maps 51% of Riley County as well drained — but another 46% drains differently: 43% moderately well drained, 2% somewhat poorly drained.
Clime is the most extensive named soil at 18% of mapped acres, then Wymore (18%) and Irwin (16%).
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 Riley County
Each reading below is measured for Riley 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 Riley County are well drained, in hydrologic group D — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Riley County runs about pH 6.0–7.5, 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
MeasuredRiley County runs about 205 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
MeasuredRiley 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 Riley County is in
Riley County spans 2 EPA Level III ecoregions — Flint Hills (95%) and Central Great Plains (5%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Riley County
We scored all 1,086 plants against Riley County's own USDA zone 6b and its own 205-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 Riley County?
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 9; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 6 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 28 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
Documented around Riley County
- Japanese beetle5 documented records
- monarch butterfly1,186 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Riley County
USGS estimates 76,476 lb of Glyphosate on Riley County farmland in 2019, its largest by weight, ahead of Atrazine (39,668 lb) and Acephate (38,953 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 Riley County — and how to grow with it.
We checked the federal record across Riley County — 381 documented sites across 7 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 Riley 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 Riley County
Closest first, across Riley County. Listing isn't leaking, and distance isn't exposure.
- 09S 06E 03BD 01Nitrate · 1.3 mi
- 09S 07E 06BC 01Nitrate · 1.9 mi
- GRIFFITH OIL CO.Underground Storage Tanks · 2.7 mi
- 08S 07E 32AAA 01Nitrate · 3.7 mi
- 09S 06E 28BC 01Nitrate · 4.2 mi
- 09S 06E 36A 01Nitrate · 4.5 mi
- RILEY COUNTY HHW FACILITYBrownfields · 4.6 mi
- CHAPMAN SERVICE STATIONUnderground Storage Tanks · 4.7 mi
- RILEY CO. FUEL STATIONUnderground Storage Tanks · 4.8 mi
- 09S 05E 01BA 01Nitrate · 5.2 mi
- 09S 05E 01BA 03Nitrate · 5.2 mi
- 09S 05E 01BCB 01Nitrate · 5.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Riley 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 Riley County.
Severity Distribution
across Riley County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Riley County, Nitrate runs higher than the national average — 144 sites across Riley County. That's not a problem with your land — it's information about 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 Riley 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 Riley County average
Your land is one point inside Riley County
Everything above resolves to Riley County as a whole — one PHZM band and one county frost record, read across 390K 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 Riley County Average
Riley County Average
- ●USDA Zones 6b, averaged across Riley County
- ●One soil character for all of Riley County
- ●Frost dates read at Riley County's scale: Apr 6 to Oct 28
YOUR Parcel
- ✓Your exact zone, not Riley County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Riley County
Pull a site-specific report for your exact address in Riley County, Kansas — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Riley County averages can't show:
We read public map data around Riley County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Riley County average
How we know this about Riley 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 Riley County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Riley County
When does frost risk typically end in Riley County?
The last hard freeze (28°F) in Riley County typically lands around Apr 6, 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 27.
How long is the growing season in Riley County?
Measured between 28°F hard freezes, Riley County sees about 205 frost-free days — roughly Apr 6 through Oct 28, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 27 to Oct 14, about 170 days.
Is the soil safe to grow vegetables in Riley County?
The federal record around Riley County is a meaningful one — 381 documented sites, mostly Nitrate entries (144), the nearest Nitrate record about 1.3 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 Riley County's scale — its 6b band and its 205-day season. Your yard writes its own version of Riley 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 Riley County’s own scale
9 of the readings below were taken at Riley County's own scale — its own ~205-day span between 28°F freezes, the 3 most extensive soil series mapped here and 381 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Riley County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Riley County's own 28°F hard-freeze dates and its ~205-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Riley CountyUSDA NRCS SSURGO
- 381 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 1.3 miles outFederal environmental registers
- Riley County's boundary and the 390,182 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~205-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Riley County spans, Flint Hills the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Riley County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Riley 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 Riley County — the ~205 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 Riley County's 390,182 acreswhy one lot differs from the next →
- Which of those 381 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 Riley Countyread your own land →