Illinois spans USDA hardiness zones 5a-7b, with a growing season of about 212 frost-free days — time enough for slow-finishing crops, second sowings, and a genuine fall garden.
The growing year is built on 34-48 inches of annual rainfall, a median of roughly 3,352 growing-degree days (base 50°F), and about 2,500 winter chill hours for tree fruit, and every crop choice answers to them. Most ground here falls among prairie loam, silt loam, clay loam, and alluvial, whose drainage habits quietly decide which beds flourish. No single calendar covers Illinois: Driftless Area, Shawnee Hills / Southern Illinois (Little Egypt), and Chicagoland (Chicago metro / lakeshore) each open and close their seasons on their own schedule. Reliable performers under these conditions include sweet corn, tomato, pumpkin, and apple; what your own ground favors still comes down to its 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
Illinois spans zones 5a-7b, 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 Illinois — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Distinct growing regions within Illinois — each has its own zones, soils, and signature crops.
Illinois: USDA zones 5a-7b, 177–244 frost-free days depending on the county, 102 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 Illinois's own county record — Jo Daviess County's measured 28°F normal, not a modeled floor.
Illinois does not have one growing season. Across all 1427 of its towns that carry their own 30-year record, the shortest measured season is Mount Carroll's at 177 days and the longest is Mounds's at 245 — a 68-day spread inside one state.
Neither end is a lone reading — another 21 towns measure within 10 days of Mount Carroll and 37 sit within 10 days of Mounds. 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 5a-7b is Illinois's average, not your lot's — a low corner or a tree line moves it. Against Illinois's 212-day season, see what your own ground reads.
One answer for Illinois averages 102 counties whose growing seasons are 67 days apart — from 177 frost-free days in Jo Daviess County to 244 in Alexander 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 102 counties runs 203–221 days, with a median of 212 days — a 67-day span end to end.
Measured across 102 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 Illinois runs 203–221 frost-free days, and 44 of its 102 counties sit outside that — 22 on the short side, 22 on the long. A statewide planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 203 frost-free days
22 counties
3 of 22 shown
The end of the state that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
203–221 frost-free days
58 counties
0 of 58 shown
The middle half of the state, and the part a single statewide date describes well.
Over 221 frost-free days
22 counties
3 of 22 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 Illinois — 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. The crumb structure that prairie roots built lets water in and holds it like a sponge, releasing it steadily through the season.
What thrives
This is some of the most productive crop ground on Earth — corn, beans, squash, brassicas, and nearly any vegetable you plant. Prairie natives like coneflower and big bluestem are, unsurprisingly, right at home.
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 Illinois'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 Illinois, cool-season planting typically opens about four weeks before the local last hard freeze — county medians put that freeze near Apr 2, with the middle half of counties between Mar 29 and Apr 8 (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 28 and Nov 5 — 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.
The plants Illinois put its name on — cultural emblems, not growing recommendations.
Violet
Viola
Designated 1907.
Quercus alba
Designated 1973. In our plant library — see its full growing profile.
GoldRush Apple
Designated 2007.
Designated 2015. In our plant library — see its full growing profile.
Plants the USDA PLANTS Database documents as native and present in Illinois — a real per-state range, not just a zone match. Ordered by how closely each plant’s published hardiness range matches Illinois’s zones 5a-7b, 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 Illinois’s USDA zones 5a-7b 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.
Heavy clay soils in northern IL drain poorly
A raised bed solves the standing-water problem in a weekend; fall compost keeps improving the clay beneath it.
Extreme temperature swings between summer and winter
Wide swings reward truly hardy varieties and a deep mulch blanket — insulation smooths what the weather won't.
Japanese beetles are a major garden pest
Hand-pick into soapy water early and often, and skip the traps (they attract more than they catch) — extension IPM guides have the rest.
For cultivar selection, pest pressure, and planting-time guidance specific to Illinois, the University of Illinois Extension is the authoritative local source.
Safe to Grow Here?What the federal record shows across Illinois — and how to grow with it.
We checked the federal record across Illinois — 52,971 documented sites across 8 of the 9 source types we track.
The most significant on record: 622 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Illinois 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 Illinois
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Illinois, two things run higher than the national average across Illinois — PFAS (482 sites) and Toxics Release Inventory (3,504 sites). That's not a problem with your land — it's information about it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Everything above resolves to Illinois as a whole — a state whose own counties record seasons 67 days apart, and hardiness across zones 5a-7b. 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 Illinois averages can't show:
We read public map data around Illinois — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Illinois 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.
Illinois spans USDA hardiness zones 5a-7b — which is to say winter's coldest night runs from about −20°F to 10°F depending where in Illinois 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 Illinois, cool-season planting typically opens about four weeks before the local last hard freeze — county medians put that freeze near Apr 2, with the middle half of counties between Mar 29 and Apr 8 (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 28 and Nov 5 — 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.
Across Illinois, the middle half of counties see their last hard freeze (28°F) between about Mar 29 and Apr 8, with a county median near Apr 2 (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 Apr 23.
Measured between 28°F hard freezes, growing seasons across Illinois's counties mostly run about 203 to 221 days, with a county median near 212 (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.
Illinois's zones 5a-7b support a wide range — strong performers include Sweet Corn, Tomato, Pumpkin, Apple, and Coneflower. 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, Illinois spans USDA zones 5a-7b (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 Illinois runs heavier than most — 52,971 documented sites, mostly Underground Storage Tanks entries (28,231) — 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. Illinois spans USDA zones 5a-7b, which sets what survives winter; last hard freezes range from about Mar 29 to Apr 8 across its counties (NOAA 1991–2020 climate normals); and 52,971 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 Illinois's scale — its 5a-7b band and its 212-day season. Your yard writes its own version of Illinois'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 Illinois's own scale — the full zone 5a-7b span inside its borders, the 4 soil types that dominate its ground and 52,971 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 Illinois.
