Clayton County, in Iowa, sits in USDA hardiness zone 4b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Reliable performers under these conditions include cabbage, cranberry, turkish rocket, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Clayton County lies within the Driftless Area — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Clayton County holds more than one microclimate.
Soils and elevations shift across Clayton 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 Clayton County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Clayton County — the short answer
Clayton County, Iowa: USDA zone 4b, about 185 days between hard freezes, across 498K acres.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 17
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 19
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~185
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 498K 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 4b is Clayton County's average, not your lot's — a low corner or a tree line moves it. Against Clayton County's 185-day season, see what your own ground reads.
Heat in Clayton County
Across a year, Clayton County accumulates about 2,455 growing degree days above 50°F, about 289 fewer than the middle Iowa county — ahead of 12 of Iowa’s 99 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 Clayton County
Across Clayton County, the ground is predominantly Alfisols, where Fayette, Downs, and Nordness are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.2–6.5, slightly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
12%
Hydric soils
6%
Soil still varies lot by lot — soil types explained.
How the ground varies across Clayton County
The USDA soil survey maps 82% of Clayton County as well drained — but another 16% drains differently: 7% moderately well drained, 6% poorly drained.
Fayette is the most extensive named soil at 43% of mapped acres, then Downs (13%) and Nordness (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 Clayton County
Each reading below is measured for Clayton 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 Clayton County are well drained, in hydrologic group C — 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 Clayton County runs about pH 6.2–6.5, 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
MeasuredClayton County runs about 185 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
MeasuredClayton County sits in USDA hardiness zone 4b.
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 Clayton County is in
Clayton County sits in the Driftless Area — EPA Level III, inside the wider Eastern Temperate Forests. One consistent ecological setting across the whole county.
What Grows in Clayton County
We scored all 1,086 plants against Clayton County's own USDA zone 4b and its own 185-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 Iowa profile.
Is it too late to plant in Clayton 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 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 17 (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.
Documented around Clayton County
- Japanese beetle1 documented records
- monarch butterfly1,929 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Clayton County
USGS estimates 194,218 lb of Glyphosate on Clayton County farmland in 2019, its largest by weight, ahead of Acetochlor (115,340 lb) and Atrazine (71,820 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 Clayton County — and how to grow with it.
We checked the federal record across Clayton County — 287 documented sites across 6 of the 9 source types we track.
The most significant on record: 7 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
Clayton County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Clayton County
Closest first, across Clayton County. Listing isn't leaking, and distance isn't exposure.
- ELKADER AIRPORTUnderground Storage Tanks · 1.8 mi
- IOWA DEPARTMENT OF TRANSPORTATIONBrownfields · 3.2 mi
- IDOTUnderground Storage Tanks · 3.3 mi
- COUNTRYSIDE AUTO REBUILDERSBrownfields · 3.6 mi
- FAST TRACK CONOCOUnderground Storage Tanks · 3.6 mi
- 093N04W07AA 01891 1944Clayton County HomeNitrate · 3.6 mi
- Elkader MineMining · 3.6 mi
- INNOVATE AG SERVICESUnderground Storage Tanks · 4.0 mi
- 093N05W23ABBB 18420 1965Elkader 5Nitrate · 4.0 mi
- MOBILE TRACK SOLUTIONSBrownfields · 4.0 mi
- CITY OF ELKADER CITY SHOPUnderground Storage Tanks · 4.0 mi
- CATERPILLAR WORK TOOLSToxics Release Inventory · 4.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Clayton 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 Clayton County.
Total Sites
287
across Clayton County
Risk Level
High
Highest-severity
7 Toxics Release Inventory facilities
Sources Checked
across Clayton County
Severity Distribution
across Clayton County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Clayton County, two things run higher than the national average across Clayton County — Mining (19 sites) and Nitrate (90 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Clayton 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 Clayton County average
Your land is one point inside Clayton County
Everything above resolves to Clayton County as a whole — one PHZM band and one county frost record, read across 498K 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 Clayton County Average
Clayton County Average
- ●USDA Zones 4b, averaged across Clayton County
- ●One soil character for all of Clayton County
- ●Frost dates read at Clayton County's scale: Apr 17 to Oct 19
YOUR Parcel
- ✓Your exact zone, not Clayton County's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Clayton County
Pull a site-specific report for your exact address in Clayton County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Clayton County averages can't show:
We read public map data around Clayton County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Clayton County average
How we know this about Clayton 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 Clayton County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Clayton County
When does frost risk typically end in Clayton County?
The last hard freeze (28°F) in Clayton County typically lands around Apr 17, 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 8.
How long is the growing season in Clayton County?
Measured between 28°F hard freezes, Clayton County sees about 185 frost-free days — roughly Apr 17 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 8 to Oct 5, about 150 days.
Is the soil safe to grow vegetables in Clayton County?
The federal record around Clayton County runs heavier than most — 287 documented sites, mostly Underground Storage Tanks entries (147), the nearest Underground Storage Tanks record about 1.8 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.
Everything above is measured at Clayton County's scale — its 4b band and its 185-day season. Your yard writes its own version of Clayton 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 Iowa's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Clayton County’s own scale
9 of the readings below were taken at Clayton County's own scale — its own ~185-day span between 28°F freezes, the 3 most extensive soil series mapped here and 287 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Clayton County's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Clayton County's own 28°F hard-freeze dates and its ~185-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Clayton CountyUSDA NRCS SSURGO
- 287 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.8 miles outFederal environmental registers
- Clayton County's boundary and the 498,216 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~185-day seasonGrowable Ground crop-matching engine
- Clayton County sitting wholly inside the Driftless AreaUS EPA Level III Ecoregions
- Open occurrence records documented in Clayton County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Clayton County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
What this page can’t tell you
- How the season shifts across Clayton County — the ~185 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 Clayton County's 498,216 acreswhy one lot differs from the next →
- Which of those 287 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 Clayton Countyread your own land →