South Wilmington, Illinois, sits in USDA hardiness zone 5b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Among the crops suited to this profile: cabbage, cranberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in South Wilmington, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single South Wilmington lot. 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 South Wilmington — soil, climate, flood, and parcel records. How we handle your address.
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South Wilmington — the short answer
South Wilmington, Illinois: USDA zone 5b, about 198 days between hard freezes, across 315 acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 12
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 27
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~198
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 315 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 5b is South Wilmington's average, not your lot's — a low corner or a tree line moves it. Against South Wilmington's 198-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in South Wilmington
Each reading below is measured for South Wilmington itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSouth Wilmington runs about 198 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
MeasuredSouth Wilmington sits in USDA hardiness zone 5b.
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 South Wilmington is in
South Wilmington sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at South Wilmington's own centroid rather than borrowed from Grundy County.
What Grows in South Wilmington
Every plant below cleared South Wilmington's own zone 5b and its 198-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in South Wilmington?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 15; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 12 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 27 — 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.
What's on the federal record near South Wilmington
Closest first, within ~10 miles of South Wilmington. Listing isn't leaking, and distance isn't exposure.
- South Wilmington Minit Mart #616Underground Storage Tanks · 1300 ft
- Dutchs ServicentarUnderground Storage Tanks · 1300 ft
- Tilley'S Service Center IncUnderground Storage Tanks · 0.8 mi
- AMERICAN BULLDOG TOWING & RECOVERY CORPBrownfields · 1.5 mi
- Fatlan Trucking IncUnderground Storage Tanks · 1.5 mi
- Serena Enco ServiceUnderground Storage Tanks · 1.6 mi
- Village Of GardnerUnderground Storage Tanks · 1.6 mi
- #019610Underground Storage Tanks · 1.7 mi
- MRV MOTOR SPORTS LLCBrownfields · 1.8 mi
- Tri Oil Co IncUnderground Storage Tanks · 1.8 mi
- Suddick, Robert and SueUnderground Storage Tanks · 1.8 mi
- BROWNE PRODUCTS COBrownfields · 2.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from South Wilmington'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 South Wilmington.
Total Sites
138
within ~10 miles of South Wilmington
Risk Level
Elevated
Highest-severity
4 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of South Wilmington
Severity Distribution
within ~10 miles of South Wilmington
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around South Wilmington, two things run higher than the national average within ~10 miles of South Wilmington — PFAS (4 sites) and Underground Storage Tanks (89 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.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in South Wilmington
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 South Wilmington average
Your land is one point inside South Wilmington
Everything above resolves to South Wilmington as a whole — one PHZM band and one 28°F frost record, read across 315 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 town 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 local average.
Your Lot vs the South Wilmington Average
South Wilmington Average
- ●USDA Zones 5b, averaged across South Wilmington
- ●One soil character for all of South Wilmington
- ●Frost dates read at South Wilmington's scale: Apr 12 to Oct 27
YOUR Parcel
- ✓Your exact zone, not South Wilmington's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in South Wilmington
Pull a site-specific report for your exact address in South Wilmington, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that South Wilmington averages can't show:
We read public map data around South Wilmington — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the South Wilmington average
How we know this about South Wilmington
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at South Wilmington’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about South Wilmington
When does frost risk typically end in South Wilmington?
The last hard freeze (28°F) in South Wilmington typically lands around Apr 12, 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 3.
When is the first frost in South Wilmington?
The first hard freeze (28°F) in South Wilmington typically arrives around Oct 27, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 13, so the watching starts about Sep 27 — about 198 days after the spring freeze cleared.
How long is the growing season in South Wilmington?
Measured between 28°F hard freezes, South Wilmington sees about 198 frost-free days — roughly Apr 12 through Oct 27, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 3 to Oct 13, about 163 days.
Is the soil safe to grow vegetables in South Wilmington?
The federal record around South Wilmington is a meaningful one — 138 documented sites, mostly Underground Storage Tanks entries (89), the nearest Underground Storage Tanks record about 0.2 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.
How do I protect my plants from frost in South Wilmington?
From about Sep 27 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 27 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 27. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at South Wilmington's scale — its 5b band and its 198-day season. Your yard writes its own version of South Wilmington's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at South Wilmington’s own scale
6 of the readings below were taken at South Wilmington's own scale — its own ~198-day season between 28°F freezes, the 315 acres it covers and 138 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- South Wilmington's own USDA hardiness band, zones 5bUSDA PHZM 2023
- South Wilmington's own 28°F hard-freeze dates, about Apr 12 and Oct 27 and the ~198-day span between themNOAA 1991–2020 Climate Normals
- 138 documented contamination sites on the federal record near South Wilmington, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- South Wilmington's boundary and the 315 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~198-day seasonGrowable Ground crop-matching engine
- The ecoregion at South Wilmington's own centroid, the Central Corn Belt PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so South Wilmington's 315 acres read through its county's SSURGO summaryfrom Grundy County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Grundy County
- The growing challenges every Illinois grower plans around — written at state scale, so they stay on the state guidefrom Illinois
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Grundy County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among South Wilmington's 315 acreswhy one lot differs from the next →
- Which side of South Wilmington you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 315 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.2 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any South Wilmington-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisSouth Wilmington sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides