Iowa County, in Wisconsin, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Crops well matched to these conditions include cabbage, cranberry, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Iowa 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
Iowa County holds more than one microclimate.
Soils and elevations shift across Iowa 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 Iowa County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Iowa County — the short answer
Iowa County, Wisconsin: USDA zone 5a, about 183 days between hard freezes, across 488K acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 18
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 18
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~183
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 488K 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 5a is Iowa County's average, not your lot's — a low corner or a tree line moves it. Against Iowa County's 183-day season, see what your own ground reads.
Heat in Iowa County
Across a year, Iowa County accumulates about 2,384 growing degree days above 50°F, about 234 more than the middle Wisconsin county — ahead of 59 of Wisconsin’s 72 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 Iowa County
Across Iowa County, the ground is predominantly Alfisols, where Newglarus, Dodgeville, and Palsgrove are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.2–6.7, slightly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
20%
Hydric soils
3%
Soil still varies lot by lot — soil types explained.
How the ground varies across Iowa County
The USDA soil survey maps 80% of Iowa County as well drained — but another 19% drains differently: 6% moderately well drained, 5% somewhat poorly drained.
Newglarus is the most extensive named soil at 20% of mapped acres, then Dodgeville (15%) and Palsgrove (10%).
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 Iowa County
Each reading below is measured for Iowa 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 Iowa 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 Iowa County runs about pH 6.2–6.7, 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
MeasuredIowa County runs about 183 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
MeasuredIowa County sits in USDA hardiness zone 5a.
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 Iowa County is in
Iowa 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 Iowa County
We scored all 1,086 plants against Iowa County's own USDA zone 5a and its own 183-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 Wisconsin profile.
Is it too late to plant in Iowa County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 21; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 18 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 18 — 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 Iowa County
- Japanese beetle6 documented records
- monarch butterfly189 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Iowa County
USGS estimates 119,366 lb of Glyphosate on Iowa County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (52,859 lb) and Acetochlor (42,464 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 Iowa County — and how to grow with it.
We checked the federal record across Iowa County — 795 documented sites across 6 of the 9 source types we track.
The most significant on record: 3 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
Iowa 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 Iowa County
Closest first, across Iowa County. Listing isn't leaking, and distance isn't exposure.
- DODGELAND HARVESTOREUnderground Storage Tanks · 1800 ft
- Unnamed MineMining · 2300 ft
- Rule Construction LtdUnderground Storage Tanks · 0.6 mi
- Unnamed Lead MineMining · 1.0 mi
- Governor Dodge State ParkUnderground Storage Tanks · 1.2 mi
- DODGEVILLE WATERWORKSPFAS · 1.5 mi
- Cathy B. Wolfe MineMining · 1.5 mi
- WILBUR EVANS JRUnderground Storage Tanks · 1.5 mi
- HENNESSEY IMPLEMENT INCBrownfields · 1.6 mi
- Walnut Hollow Farm IncUnderground Storage Tanks · 1.6 mi
- HEALTHSTAT HEALTH AND WELLNESS CENTER - LANDS END CLINICBrownfields · 1.6 mi
- LANDS END - PHONE CENTERBrownfields · 1.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Iowa 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 Iowa County.
Sources Checked
across Iowa County
Severity Distribution
across Iowa County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Iowa County, Mining runs higher than the national average — 464 sites across Iowa County. That's not a problem with your land — it's information about 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.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Iowa 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 Iowa County average
Your land is one point inside Iowa County
Everything above resolves to Iowa County as a whole — one PHZM band and one county frost record, read across 488K 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 Iowa County Average
Iowa County Average
- ●USDA Zones 5a, averaged across Iowa County
- ●One soil character for all of Iowa County
- ●Frost dates read at Iowa County's scale: Apr 18 to Oct 18
YOUR Parcel
- ✓Your exact zone, not Iowa County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Iowa County
Pull a site-specific report for your exact address in Iowa County, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Iowa County averages can't show:
We read public map data around Iowa County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Iowa County average
How we know this about Iowa 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 Iowa County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Iowa County
When does frost risk typically end in Iowa County?
The last hard freeze (28°F) in Iowa County typically lands around Apr 18, 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 9.
How long is the growing season in Iowa County?
Measured between 28°F hard freezes, Iowa County sees about 183 frost-free days — roughly Apr 18 through Oct 18, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 9 to Oct 4, about 148 days.
Is the soil safe to grow vegetables in Iowa County?
The federal record around Iowa County runs heavier than most — 795 documented sites, mostly Mining entries (464), the nearest Underground Storage Tanks record about 0.3 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 Iowa County's scale — its 5a band and its 183-day season. Your yard writes its own version of Iowa 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 Wisconsin's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Iowa County’s own scale
9 of the readings below were taken at Iowa County's own scale — its own ~183-day span between 28°F freezes, the 3 most extensive soil series mapped here and 795 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Iowa County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Iowa County's own 28°F hard-freeze dates and its ~183-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Iowa CountyUSDA NRCS SSURGO
- 795 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 0.3 miles outFederal environmental registers
- Iowa County's boundary and the 488,127 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~183-day seasonGrowable Ground crop-matching engine
- Iowa County sitting wholly inside the Driftless AreaUS EPA Level III Ecoregions
- Open occurrence records documented in Iowa County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Iowa County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Wisconsin grower plans around — written at state scale, so they stay on the state guidefrom Wisconsin
What this page can’t tell you
- How the season shifts across Iowa County — the ~183 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 Iowa County's 488,127 acreswhy one lot differs from the next →
- Which of those 795 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 Iowa Countyread your own land →