Calhoun County, in Illinois, sits in USDA hardiness zone 6b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Expect cabbage, hazelnut, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Calhoun County holds more than one microclimate.
Soils and elevations shift across Calhoun 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 Calhoun County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Calhoun County — the short answer
Calhoun County, Illinois: USDA zone 6b, about 221 days between hard freezes, across 162K acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 29
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 5
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~221
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 162K 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 6b is Calhoun County's average, not your lot's — a low corner or a tree line moves it. Against Calhoun County's 221-day season, see what your own ground reads.
Heat in Calhoun County
Across a year, Calhoun County accumulates about 3,705 growing degree days above 50°F, about 322 more than the middle Illinois county — ahead of 70 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.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Calhoun County
Across Calhoun County, the ground is predominantly Alfisols, where Stookey, Beaucoup, and Menfro are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 5.9–6.7, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
9%
Hydric soils
16%
Soil still varies lot by lot — soil types explained.
How the ground varies across Calhoun County
The USDA soil survey maps 62% of Calhoun County as well drained — but another 26% drains differently: 11% somewhat poorly drained, 11% poorly drained.
Stookey is the most extensive named soil at 44% of mapped acres, then Beaucoup (12%) and Menfro (10%).
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 Calhoun County
Each reading below is measured for Calhoun 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 Calhoun 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 Calhoun County runs about pH 5.9–6.7, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Wet ground
MeasuredAbout 16% of Calhoun County is mapped as hydric — wetland — soil.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Season length
MeasuredCalhoun County runs about 221 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
The kind of country Calhoun County is in
Calhoun County sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. One consistent ecological setting across the whole county.
What Grows in Calhoun County
We scored all 1,086 plants against Calhoun County's own USDA zone 6b and its own 221-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 Calhoun County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 29 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 5 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
Documented around Calhoun County
Survey cells within 31 miles of Calhoun County checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 224 miles off. What to watch for.
- monarch butterfly2 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Calhoun County
USGS estimates 30,731 lb of Glyphosate on Calhoun County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (15,284 lb) and Atrazine (14,242 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 Calhoun County — and how to grow with it.
We checked the federal record across Calhoun County — 26 documented sites across 2 of the 9 source types we track.
The most significant on record: 2 brownfield sites. Former commercial or industrial land where legacy contamination may persist.
The federal record across Calhoun County is light. Growing food here starts from a strong position — a quick pass over the map tells you whether any recorded site sits near your land, and if one does, that's information to plant with, not a reason to stop.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Calhoun County
Closest first, across Calhoun County. Listing isn't leaking, and distance isn't exposure.
- Roger GressUnderground Storage Tanks · 2.2 mi
- Richter Fertilizer Co IncUnderground Storage Tanks · 2.5 mi
- Geisler Energy IncUnderground Storage Tanks · 2.5 mi
- Northside Family Foods Inc.Underground Storage Tanks · 2.5 mi
- Midway Stop & ShopUnderground Storage Tanks · 2.5 mi
- Quillers OutboardUnderground Storage Tanks · 2.5 mi
- Munsterman Shell StationUnderground Storage Tanks · 2.6 mi
- Ayerco #29 Convenience CenterUnderground Storage Tanks · 2.6 mi
- WARECO 233Brownfields · 2.6 mi
- E W of HardinUnderground Storage Tanks · 2.7 mi
- Calhoun High SchoolUnderground Storage Tanks · 3.1 mi
- Calhoun QuarryUnderground Storage Tanks · 4.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Calhoun 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 Calhoun County.
Severity Distribution
across Calhoun County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Calhoun County, Underground Storage Tanks runs higher than the national average — 24 sites across Calhoun County. That's not a problem with your land — it's information about it.
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 Calhoun 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 Calhoun County average
Your land is one point inside Calhoun County
Everything above resolves to Calhoun County as a whole — one PHZM band and one county frost record, read across 162K 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 Calhoun County Average
Calhoun County Average
- ●USDA Zones 6b, averaged across Calhoun County
- ●One soil character for all of Calhoun County
- ●Frost dates read at Calhoun County's scale: Mar 29 to Nov 5
YOUR Parcel
- ✓Your exact zone, not Calhoun County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Calhoun County
Pull a site-specific report for your exact address in Calhoun County, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Calhoun County averages can't show:
We read public map data around Calhoun County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Calhoun County average
How we know this about Calhoun 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 Calhoun County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Calhoun County
When does frost risk typically end in Calhoun County?
The last hard freeze (28°F) in Calhoun County typically lands around Mar 29, 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 19.
How long is the growing season in Calhoun County?
Measured between 28°F hard freezes, Calhoun County sees about 221 frost-free days — roughly Mar 29 through Nov 5, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 19 to Oct 22, about 186 days.
Is the soil safe to grow vegetables in Calhoun County?
The federal record around Calhoun County is light — 26 documented sites across the 9 federal source types we checked, mostly Underground Storage Tanks entries (24), the nearest Underground Storage Tanks record about 2.2 miles out — and proximity to a documented site is information, not a diagnosis of any one yard. Growing food here starts from a strong position; a soil test before new food beds settles any site-specific question.
Everything above is measured at Calhoun County's scale — its 6b band and its 221-day season. Your yard writes its own version of Calhoun 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 Calhoun County’s own scale
9 of the readings below were taken at Calhoun County's own scale — its own ~221-day span between 28°F freezes, the 3 most extensive soil series mapped here and 26 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Calhoun County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Calhoun County's own 28°F hard-freeze dates and its ~221-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Calhoun CountyUSDA NRCS SSURGO
- 26 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 2.2 miles outFederal environmental registers
- Calhoun County's boundary and the 162,451 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~221-day seasonGrowable Ground crop-matching engine
- Calhoun County sitting wholly inside the Interior River Valleys and HillsUS EPA Level III Ecoregions
- Open occurrence records documented in Calhoun County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Calhoun 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 Calhoun County — the ~221 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 Calhoun County's 162,451 acreswhy one lot differs from the next →
- Which of those 26 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 Calhoun Countyread your own land →