Hardin County, in Illinois, sits in USDA hardiness zone 7a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
A short list that earns its place here — cabbage, hazelnut, california poppy, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Hardin County lies within the Shawnee Hills / Southern Illinois (Little Egypt) — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Hardin County holds more than one microclimate.
Soils and elevations shift across Hardin County, so your frost dates and drainage aren't the county average. 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 Hardin County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Hardin County — the short answer
Hardin County, Illinois: USDA zone 7a, about 232 days between hard freezes, across 114K acres.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 24
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 11
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~232
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 114K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 Hardin County's average, not your lot's — a low corner or a tree line moves it. Against Hardin County's 232-day season, see what your own ground reads.
Heat and winter chill in Hardin County
Across a year, Hardin County accumulates about 4,039 growing degree days above 50°F, about 656 more than the middle Illinois county — ahead of 96 of Illinois’s 102 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Winter banks about 2,391 hours below 45°F. Chill is what tells a fruit tree its dormancy is over, and it is set by climate rather than by anything you can build.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Hardin County
Across Hardin County, the ground is predominantly Alfisols, where Alford, Wellston, and Grantsburg are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 5.3–5.9, moderately acidic. Rainfall drains through hydrologic group B soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
9%
Hydric soils
5%
Soil still varies lot by lot — soil types explained.
How the ground varies across Hardin County
The USDA soil survey maps 54% of Hardin County as well drained — but another 43% drains differently: 33% moderately well drained, 7% somewhat poorly drained.
Alford is the most extensive named soil at 21% of mapped acres, then Wellston (14%) and Grantsburg (12%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Hardin County
Each reading below is measured for Hardin County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Hardin County are well drained, in hydrologic group B — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Hardin County runs about pH 5.3–5.9, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Season length
MeasuredHardin County runs about 232 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
MeasuredHardin County 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 Hardin County is in
Hardin County spans 2 EPA Level III ecoregions — Interior Plateau (93%) and Interior River Valleys and Hills (7%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Hardin County
We scored all 1,086 plants against Hardin County's own USDA zone 7a and its own 232-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Illinois profile.
Is it too late to plant in Hardin County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Feb 24; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 24 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 11 — 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.
Documented around Hardin County
Survey cells within 31 miles of Hardin County checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 129 miles off. What to watch for.
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Hardin County
USGS estimates 3,715 lb of Glyphosate on Hardin County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (3,418 lb) and Atrazine (3,146 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Hardin County — and how to grow with it.
We checked the federal record across Hardin County — 85 documented sites across 6 of the 9 source types we track.
The most significant on record: 2 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Hardin County 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.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Hardin County
Closest first, across Hardin County. Listing isn't leaking, and distance isn't exposure.
- Raines Bus LineUnderground Storage Tanks · 1.8 mi
- Kaskaskia Experimental ForestUnderground Storage Tanks · 1.8 mi
- Hardin County Hwy DeptUnderground Storage Tanks · 3.0 mi
- Robinson Oil CompanyUnderground Storage Tanks · 3.0 mi
- Hardin County K-12 SchoolUnderground Storage Tanks · 3.0 mi
- Lead Hill MineMining · 3.1 mi
- Victory MineMining · 3.3 mi
- Alco-Palmer Lead MineMining · 3.5 mi
- Patrick MineMining · 3.5 mi
- Cave In Rock Quadrangle MineMining · 3.6 mi
- Deardorff Mine No. 1Mining · 3.7 mi
- Spivey MineMining · 3.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Hardin County'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 Hardin County.
Sources Checked
across Hardin County
Severity Distribution
across Hardin County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Hardin County, Mining runs higher than the national average — 47 sites across Hardin County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Hardin County
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 Hardin County average
Your land is one point inside Hardin County
Everything above resolves to Hardin County as a whole — one PHZM band and one county frost record, read across 114K 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 county 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 county average.
Your Lot vs the Hardin County Average
Hardin County Average
- ●USDA Zones 7a, averaged across Hardin County
- ●One soil character for all of Hardin County
- ●Frost dates read at Hardin County's scale: Mar 24 to Nov 11
YOUR Parcel
- ✓Your exact zone, not Hardin County's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Hardin County
Pull a site-specific report for your exact address in Hardin County, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Hardin County averages can't show:
We read public map data around Hardin County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Hardin County average
How we know this about Hardin County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Hardin County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Hardin County
When does frost risk typically end in Hardin County?
The last hard freeze (28°F) in Hardin County typically lands around Mar 24, 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 14.
How long is the growing season in Hardin County?
Measured between 28°F hard freezes, Hardin County sees about 232 frost-free days — roughly Mar 24 through Nov 11, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 14 to Oct 28, about 197 days.
Is the soil safe to grow vegetables in Hardin County?
The federal record around Hardin County runs heavier than most — 85 documented sites, mostly Mining entries (47), the nearest Underground Storage Tanks record about 1.8 miles out — 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.
Everything above is measured at Hardin County's scale — its 7a band and its 232-day season. Your yard writes its own version of Hardin County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Illinois's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Hardin County’s own scale
9 of the readings below were taken at Hardin County's own scale — its own ~232-day span between 28°F freezes, the 3 most extensive soil series mapped here and 85 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Hardin County's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Hardin County's own 28°F hard-freeze dates and its ~232-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Hardin CountyUSDA NRCS SSURGO
- 85 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.8 miles outFederal environmental registers
- Hardin County's boundary and the 113,530 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~232-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Hardin County spans, Interior Plateau the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Hardin County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Hardin County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Illinois grower plans around — written at state scale, so they stay on the state guidefrom Illinois
What this page can’t tell you
- How the season shifts across Hardin County — the ~232 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hardin County's 113,530 acreswhy one lot differs from the next →
- Which of those 85 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Hardin Countyread your own land →