Iowa spans USDA hardiness zones 4b-6a, with a growing season of about 189 frost-free days — a true four-season rhythm: spring greens, a full summer main crop, and a fall window that rewards planning.
The raw materials of the growing year here: 26-36 inches of annual rainfall, a median of roughly 2,730 growing-degree days (base 50°F), and about 2,500 winter chill hours for tree fruit. Underfoot it's mostly prairie loess, silt loam, clay loam, and alluvial — and how those drain decides more about crop success than almost anything else. What grows in Iowa depends on where in it you stand — Driftless Area, Southeast Iowa / Great River Region (Mississippi–Des Moines river corner), and Loess Hills each run on their own zones and frost timing. The conditions favor sweet corn, tomato, apple, and grape, among others — though every individual site edits that list with its own soil, sun, and drainage.
Grounded inUSDA PHZM•NOAA Climate Normals•USDA NRCS SSURGO•GDD (PRISM 1991-2020 normals)•Chill hours (PRISM 1991-2020 normals)•USDA hardiness sub-region map•EPA FRS•USDA PLANTS•Growable Ground suitability scoring
Iowa spans zones 4b-6a, but your yard sits in exactly one — and slope, tree cover, and low spots nudge it further. 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 — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Distinct growing regions within Iowa — each has its own zones, soils, and signature crops.
Iowa: USDA zones 4b-6a, 168–216 frost-free days depending on the county, 99 counties.
The middle half of this state’s counties. Tender transplants usually wait 2–3 weeks past the last hard freeze. The shortest-season figure is Iowa's own county record — Howard County's measured 28°F normal, not a modeled floor.
Iowa does not have one growing season. Across all 1001 of its towns that carry their own 30-year record, the shortest measured season is Cresco's at 165 days and the longest is Sandusky's at 224 — a 59-day spread inside one state.
Neither end is a lone reading — another 28 towns measure within 10 days of Cresco and 17 sit within 10 days of Sandusky. These are real pockets, so the number to plant against is your own town's, not the state average.
NOAA Regional Climate Centers ACIS (1991–2020), 30-year daily minimum record
Zone 4b-6a is Iowa's average, not your lot's — a low corner or a tree line moves it. Against Iowa's 189-day season, see what your own ground reads.
One answer for Iowa averages 99 counties whose growing seasons are 48 days apart — from 168 frost-free days in Howard County to 216 in Lee County. That is the same state, measured the same way, in the same years. Which end of it your county sits nearer decides what finishes before the first hard freeze.
The middle half of 99 counties runs 183–197 days, with a median of 189 days — a 48-day span end to end.
Measured across 99 counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze. A county with no record of its own is absent from the range rather than counted as zero — nothing here is interpolated to the state. Your own site sits somewhere inside this range; a parcel report resolves where.
The middle half of Iowa runs 183–197 frost-free days, and 42 of its 99 counties sit outside that — 21 on the short side, 21 on the long. A statewide planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 183 frost-free days
21 counties
3 of 21 shown
The end of the state that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
183–197 frost-free days
57 counties
0 of 57 shown
The middle half of the state, and the part a single statewide date describes well.
Over 197 frost-free days
21 counties
3 of 21 shown
Long enough for a second succession of a quick crop after the first comes out.
Each county is placed by its own 28°F frost-free normal (NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze), the same figure its own guide page publishes. Elevation, slope and cold-air drainage move a yard within its county as well — which is the part only your address resolves.
The soil types that dominate Iowa — how each drains decides more about crop success than almost anything else. Tap any soil to learn what it is and how to work with it. Each photo is a representative profile of that soil type; the named series is where it was documented, which is often another state.
Drainage
Good — it absorbs rain readily and holds it in reach of roots — but it erodes faster than any other soil when left bare on a slope.
What thrives
Nearly everything: corn, small grains, and the full vegetable garden thrive in loess country, which is exactly why so much of it is farmed.
Drainage
Moderate. Silt holds water well and releases it steadily, though the fine particles can crust after hard rain and compact under traffic.
What thrives
The full vegetable garden does well here, and small grains, corn, and leafy greens are classic silt-loam crops. Its steady moisture suits shallow-rooted plants that dislike drought stress.
Loam tilted toward clay — heavier in the hand, slower to dry, and richer in nutrients than its sandier cousins. Clay particles carry a surface charge that holds fertilizer and minerals where roots can reach them.
Drainage
Slow to moderate. Water lingers in the root zone longer than in loam, which is a gift in dry summers and a challenge in wet springs.
What thrives
Heavy feeders that appreciate steady moisture — brassicas, corn, beans, and many fruit trees. Perennials with strong root systems establish well once they are through the first season.
Drainage
Usually good: rivers sort their loads, and most alluvial soils have enough sand and silt to move water while holding plenty for roots. Low-lying pockets can run wet.
What thrives
Nearly everything — vegetables, orchards, vines, and berries all prosper on alluvium. Its depth lets roots go as far down as they care to.
Soil data: USDA NRCS SSURGO · Soil types explained
Plants well-suited to Iowa's climate, soils, and growing season — each links to its full growing profile.
Rarely: the season closes in stages, not all at once, and each stage has its crops. Across Iowa, cool-season planting typically opens about four weeks before the local last hard freeze — county medians put that freeze near Apr 14, with the middle half of counties between Apr 10 and Apr 17 (NOAA 1991–2020 climate normals). Tender transplants wait two to three weeks past it, and fall planting counts back from first freezes mostly between Oct 18 and Oct 23 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
The plants Iowa put its name on — cultural emblems, not growing recommendations.
Wild prairie rose
Rosa arkansana
Designated 1897.
Oak
Quercus spp.
Designated 1961.
Plants the USDA PLANTS Database documents as native and present in Iowa — a real per-state range, not just a zone match. Ordered by how closely each plant’s published hardiness range matches Iowa’s zones 4b-6a, so this is a shortlist by climate fit, not a ranking of which plants matter most here. Presence is statewide, so a plant may still be uncommon in your specific county; your state’s Cooperative Extension or a native-plant society is the local authority.
US-native plants whose hardiness range overlaps Iowa’s USDA zones 4b-6a but which USDA PLANTS doesn’t map to a single state range here. Zone overlap is a starting filter, not a range map.
What an experienced grower plans around here — each one has a move.
Cold winters reaching -20F or below
Choose perennials rated a zone hardier than yours — Iowa winters test the margins, and the margin is where plants are lost.
Variable spring weather delays planting
Let soil temperature and your local frost normal call the start, not the calendar — a two-week wait beats a replant.
Wind exposure on open prairies desiccates plants
Even a simple windbreak — a shrub row, a snow fence, a tall cover crop — cuts wind desiccation dramatically.
For cultivar selection, pest pressure, and planting-time guidance specific to Iowa, the Iowa State University Extension and Outreach is the authoritative local source.
Safe to Grow Here?What the federal record shows across Iowa — and how to grow with it.
We checked the federal record across Iowa — 28,062 documented sites across 8 of the 9 source types we track.
The most significant on record: 122 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Iowa 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.
Severity Distribution
across Iowa
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Iowa, Nitrate runs higher than the national average — 8,028 sites across Iowa. 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).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Everything above resolves to Iowa as a whole — a state whose own counties record seasons 48 days apart, and hardiness across zones 4b-6a. Your parcel sits at one point in that range, not in the middle of it. 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 state 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 statewide average.
State averages sketch the shape. Your soil, sun exposure, drainage, and microclimate decide what actually takes. Pull a site-specific report for your exact parcel.
Enter your address. We read your soil, sun, drainage, and frost dates, then score 1,086 plants against the real conditions on your land.
Three things about your lot that Iowa averages can't show:
We read public map data around Iowa — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Iowa average
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read per county and aggregated to the state band; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each county’s own record; rainfall from NOAA Climate Normals; soils from USDA NRCS SSURGO; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above. Where a county carries no record of its own, it is absent from the figure rather than filled in.
Iowa spans USDA hardiness zones 4b-6a — which is to say winter's coldest night runs from about −25°F to −5°F depending where in Iowa you are, averaged over 1991–2020 (USDA PHZM 2023).
Rarely: the season closes in stages, not all at once, and each stage has its crops. Across Iowa, cool-season planting typically opens about four weeks before the local last hard freeze — county medians put that freeze near Apr 14, with the middle half of counties between Apr 10 and Apr 17 (NOAA 1991–2020 climate normals). Tender transplants wait two to three weeks past it, and fall planting counts back from first freezes mostly between Oct 18 and Oct 23 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Across Iowa, the middle half of counties see their last hard freeze (28°F) between about Apr 10 and Apr 17, with a county median near Apr 14 (NOAA 1991–2020 climate normals). 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 5.
Measured between 28°F hard freezes, growing seasons across Iowa's counties mostly run about 184 to 197 days, with a county median near 189 (NOAA 1991–2020 climate normals). Tender crops get a somewhat shorter practical window, since lighter frosts reach a few weeks past the hard-freeze dates on both ends.
Iowa's zones 4b-6a support a wide range — strong performers include Sweet Corn, Tomato, Apple, Grape, and Hosta. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Officially, Iowa spans USDA zones 4b-6a (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,086 plants against what's actually there.
The federal record across Iowa runs heavier than most — 28,062 documented sites, mostly Underground Storage Tanks entries (13,220) — 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.
Start with three facts. Iowa spans USDA zones 4b-6a, which sets what survives winter; last hard freezes range from about Apr 10 to Apr 17 across its counties (NOAA 1991–2020 climate normals); and 28,062 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything above is measured at Iowa's scale — its 4b-6a band and its 189-day season. Your yard writes its own version of Iowa's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
6 of the readings below were taken at Iowa's own scale — the full zone 4b-6a span inside its borders, the 4 soil types that dominate its ground and 28,062 documented sites on its federal record; anything it cannot resolve at this scale is named below.
Measured here
What this page can’t tell you
Explore growing conditions by county — each has its own zone range and land area.
Explore growing conditions by city or town in Iowa.
