Sullivan, Illinois, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Crops well matched to these conditions include cabbage, hazelnut, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Sullivan, 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 Sullivan 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 Sullivan — soil, climate, flood, and parcel records. How we handle your address.
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Sullivan — the short answer
Sullivan, Illinois: USDA zone 6a, about 211 days between hard freezes, across 2K acres of city.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 31
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~211
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 2K 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 6a is Sullivan's average, not your lot's — a low corner or a tree line moves it. Against Sullivan's 211-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Sullivan
Each reading below is measured for Sullivan itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSullivan runs about 211 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSullivan sits in USDA hardiness zone 6a.
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 Sullivan is in
Sullivan sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Sullivan's own centroid rather than borrowed from Moultrie County.
What Grows in Sullivan
Every plant below cleared Sullivan's own zone 6a and its 211-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Sullivan?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 31 — 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.
What's on the federal record near Sullivan
Closest first, within ~10 miles of Sullivan. Listing isn't leaking, and distance isn't exposure.
- Casey's General Store #1808Underground Storage Tanks · 450 ft
- E-K Petro MartUnderground Storage Tanks · 600 ft
- OK JOBBERSBrownfields · 750 ft
- FIELDS WRIGHT MEDICAL FACILITYBrownfields · 1000 ft
- Fields-Wright Medical Fac IncUnderground Storage Tanks · 1000 ft
- Gas Dept- Plant LocationUnderground Storage Tanks · 1100 ft
- D & B Refuse IncUnderground Storage Tanks · 1100 ft
- Sullivan Road DistUnderground Storage Tanks · 1100 ft
- Sullivan FarmarketUnderground Storage Tanks · 1100 ft
- Kaiser Ag Chemicals IncUnderground Storage Tanks · 1100 ft
- Jonathan Creek TownshipUnderground Storage Tanks · 1100 ft
- Sullivan Super KUnderground Storage Tanks · 1100 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Sullivan'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 Sullivan.
Total Sites
83
within ~10 miles of Sullivan
Risk Level
Moderate
Highest-severity
4 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Sullivan
Severity Distribution
within ~10 miles of Sullivan
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Sullivan, Underground Storage Tanks runs higher than the national average — 57 sites within ~10 miles of Sullivan. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Sullivan
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 Sullivan average
Your land is one point inside Sullivan
Everything above resolves to Sullivan as a whole — one PHZM band and one 28°F frost record, read across 2K 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 city 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 Sullivan Average
Sullivan Average
- ●USDA Zones 6a, averaged across Sullivan
- ●One soil character for all of Sullivan
- ●Frost dates read at Sullivan's scale: Apr 3 to Oct 31
YOUR Parcel
- ✓Your exact zone, not Sullivan's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Sullivan
Pull a site-specific report for your exact address in Sullivan, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Sullivan averages can't show:
We read public map data around Sullivan — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Sullivan average
How we know this about Sullivan
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Sullivan’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 city grain anywhere on this page — there is no city-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 Sullivan
When does frost risk typically end in Sullivan?
The last hard freeze (28°F) in Sullivan typically lands around Apr 3, 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 Apr 24.
When is the first frost in Sullivan?
The first hard freeze (28°F) in Sullivan typically arrives around Oct 31, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 17, so the watching starts about Oct 1 — about 211 days after the spring freeze cleared.
How long is the growing season in Sullivan?
Measured between 28°F hard freezes, Sullivan sees about 211 frost-free days — roughly Apr 3 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 24 to Oct 17, about 176 days.
Is the soil safe to grow vegetables in Sullivan?
The federal record around Sullivan shows 83 documented sites, mostly Underground Storage Tanks entries (57), the nearest Underground Storage Tanks record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Sullivan?
From about Oct 1 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 31 (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 31. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Sullivan's scale — its 6a band and its 211-day season. Your yard writes its own version of Sullivan'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 Sullivan’s own scale
6 of the readings below were taken at Sullivan's own scale — its own ~211-day season between 28°F freezes, the 1,772 acres it covers and 83 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Sullivan's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Sullivan's own 28°F hard-freeze dates, about Apr 3 and Oct 31 and the ~211-day span between themNOAA 1991–2020 Climate Normals
- 83 documented contamination sites on the federal record near Sullivan, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Sullivan's boundary and the 1,772 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~211-day seasonGrowable Ground crop-matching engine
- The ecoregion at Sullivan'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 Sullivan's 1,772 acres read through its county's SSURGO summaryfrom Moultrie County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Moultrie 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 Moultrie County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Sullivan's 1,772 acreswhy one lot differs from the next →
- Which side of Sullivan you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,772 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile 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 Sullivan-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisSullivan sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides