St. Johns, Illinois, sits in USDA hardiness zone 7a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Among the crops suited to this profile: cabbage, hazelnut, california poppy, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in St. Johns, 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 St. Johns 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 St. Johns — soil, climate, flood, and parcel records. How we handle your address.
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St. Johns — the short answer
St. Johns, Illinois: USDA zone 7a, about 228 days between hard freezes, across 464 acres of town.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 25
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 8
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~228
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 464 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 7a is St. Johns's average, not your lot's — a low corner or a tree line moves it. Against St. Johns's 228-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in St. Johns
Each reading below is measured for St. Johns itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSt. Johns runs about 228 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
MeasuredSt. Johns sits in USDA hardiness zone 7a.
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 St. Johns is in
St. Johns sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at St. Johns's own centroid rather than borrowed from Perry County.
What Grows in St. Johns
Every plant below cleared St. Johns's own zone 7a and its 228-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in St. Johns?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Feb 25; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 25 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 8 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
What's on the federal record near St. Johns
Closest first, within ~10 miles of St. Johns. Listing isn't leaking, and distance isn't exposure.
- ILLINOIS MPP COToxics Release Inventory · 0.6 mi
- DUQUOIN LUBRICANTS BLENDING & PACKAGING DIVToxics Release Inventory · 0.8 mi
- Old Pepsi PlantUnderground Storage Tanks · 0.9 mi
- ENCO INDUSTRIES INCBrownfields · 0.9 mi
- KROGER CO STORE 663Brownfields · 1.0 mi
- Du Quoin Han-Dee MartUnderground Storage Tanks · 1.1 mi
- Continental Baking CoUnderground Storage Tanks · 1.1 mi
- Duquoin Sewer PlantUnderground Storage Tanks · 1.2 mi
- School Bus ShedUnderground Storage Tanks · 1.4 mi
- Caseys General Store #2337Underground Storage Tanks · 1.4 mi
- GTE NorthUnderground Storage Tanks · 1.5 mi
- IL State Police Dist 13Underground Storage Tanks · 1.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from St. Johns'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 St. Johns.
Total Sites
113
within ~10 miles of St. Johns
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of St. Johns
Severity Distribution
within ~10 miles of St. Johns
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •TRI facilities report what they release. Check the wind — downwind beds catch more of it.
Check your specific parcel in St. Johns
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 St. Johns average
Your land is one point inside St. Johns
Everything above resolves to St. Johns as a whole — one PHZM band and one 28°F frost record, read across 464 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 St. Johns Average
St. Johns Average
- ●USDA Zones 7a, averaged across St. Johns
- ●One soil character for all of St. Johns
- ●Frost dates read at St. Johns's scale: Mar 25 to Nov 8
YOUR Parcel
- ✓Your exact zone, not St. Johns's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in St. Johns
Pull a site-specific report for your exact address in St. Johns, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Johns averages can't show:
We read public map data around St. Johns — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Johns average
How we know this about St. Johns
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 St. Johns’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 St. Johns
When does frost risk typically end in St. Johns?
The last hard freeze (28°F) in St. Johns typically lands around Mar 25, 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 15.
When is the first frost in St. Johns?
The first hard freeze (28°F) in St. Johns typically arrives around Nov 8, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 25, so the watching starts about Oct 9 — about 228 days after the spring freeze cleared.
How long is the growing season in St. Johns?
Measured between 28°F hard freezes, St. Johns sees about 228 frost-free days — roughly Mar 25 through Nov 8, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 15 to Oct 25, about 193 days.
Is the soil safe to grow vegetables in St. Johns?
The federal record around St. Johns is a meaningful one — 113 documented sites, mostly Underground Storage Tanks entries (69), the nearest Toxics Release Inventory record about 0.6 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 St. Johns?
From about Oct 9 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 Nov 8 (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 Nov 8. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at St. Johns's scale — its 7a band and its 228-day season. Your yard writes its own version of St. Johns'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 St. Johns’s own scale
6 of the readings below were taken at St. Johns's own scale — its own ~228-day season between 28°F freezes, the 464 acres it covers and 113 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- St. Johns's own USDA hardiness band, zones 7aUSDA PHZM 2023
- St. Johns's own 28°F hard-freeze dates, about Mar 25 and Nov 8 and the ~228-day span between themNOAA 1991–2020 Climate Normals
- 113 documented contamination sites on the federal record near St. Johns, the closest Toxics Release Inventory record about 0.6 miles out from the town centreFederal environmental registers
- St. Johns's boundary and the 464 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~228-day seasonGrowable Ground crop-matching engine
- The ecoregion at St. Johns's own centroid, the Interior River Valleys and HillsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so St. Johns's 464 acres read through its county's SSURGO summaryfrom Perry County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Perry 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 Perry County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among St. Johns's 464 acreswhy one lot differs from the next →
- Which side of St. Johns you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 464 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Toxics Release Inventory record about 0.6 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 St. Johns-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisSt. Johns sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides