Cass County, in Illinois, sits in USDA hardiness zone 6a — a zone band wide enough that plant choice, not possibility, is the interesting question.
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
Cass County holds more than one microclimate.
Soils and elevations shift across Cass 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 Cass County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Cass County — the short answer
Cass County, Illinois: USDA zone 6a, about 212 days between hard freezes, across 240K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 2
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 31
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~212
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 240K 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 6a is Cass County's average, not your lot's — a low corner or a tree line moves it. Against Cass County's 212-day season, see what your own ground reads.
Heat in Cass County
Across a year, Cass County accumulates about 3,352 growing degree days above 50°F, about 31 fewer than the middle Illinois county — ahead of 44 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 Cass County
Across Cass County, the ground is predominantly Mollisols, where Ipava, Plainfield, and Sylvan are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.2–6.8, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
30%
Hydric soils
27%
Soil still varies lot by lot — soil types explained.
How the ground varies across Cass County
The USDA soil survey maps 42% of Cass County as well drained — but another 56% drains differently: 19% somewhat poorly drained, 17% poorly drained.
Ipava is the most extensive named soil at 8% of mapped acres, then Plainfield (7%) and Sylvan (6%).
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 Cass County
Each reading below is measured for Cass 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 Cass 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 Cass County runs about pH 6.2–6.8, 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 27% of Cass 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
MeasuredCass County runs about 212 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 Cass County is in
Cass County spans 2 EPA Level III ecoregions — Interior River Valleys and Hills (92%) and Central Corn Belt Plains (8%). 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 Cass County
We scored all 1,086 plants against Cass County's own USDA zone 6a and its own 212-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 Cass County?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 5; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 2 (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.
Documented around Cass County
- monarch butterfly25 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Cass County
USGS estimates 117,578 lb of Glyphosate on Cass County farmland in 2019, its largest by weight, ahead of Atrazine (60,736 lb) and Metolachlor & Metolachlor-s (60,659 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 Cass County — and how to grow with it.
We checked the federal record across Cass County — 127 documented sites across 6 of the 9 source types we track.
The most significant on record: 3 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Cass County is a modest one — a typical footprint for a growing area. Nothing here calls for alarm; it's worth knowing which recorded sites sit closest to where you grow, and each one on the map carries its type and location. If one turns out to be a near neighbor, a one-time soil test settles the question.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Cass County
Closest first, across Cass County. Listing isn't leaking, and distance isn't exposure.
- SANGAMON COACHWORKSBrownfields · 0.5 mi
- ILDOT DIST 6Brownfields · 0.5 mi
- Bluff Springs Elevator CoUnderground Storage Tanks · 2.0 mi
- Cass County Telephone CoUnderground Storage Tanks · 2.1 mi
- Fast FuelsUnderground Storage Tanks · 2.1 mi
- Casey's General Store #3472Underground Storage Tanks · 2.2 mi
- Cass County Ser CoUnderground Storage Tanks · 2.2 mi
- DOLLAR GENERAL STORE 9182Brownfields · 2.2 mi
- REYNOLD AND SONSBrownfields · 2.3 mi
- Reynold's ServiceUnderground Storage Tanks · 2.3 mi
- Krohe RefrigerationUnderground Storage Tanks · 2.3 mi
- BPS Retail Fuels, Inc.Underground Storage Tanks · 2.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Cass 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 Cass County.
Total Sites
127
across Cass County
Risk Level
Moderate
Highest-severity
3 Toxics Release Inventory facilities
Sources Checked
across Cass County
Severity Distribution
across Cass County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Cass County, two things run higher than the national average across Cass County — CAFO (6 sites) and Underground Storage Tanks (87 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Cass 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 Cass County average
Your land is one point inside Cass County
Everything above resolves to Cass County as a whole — one PHZM band and one county frost record, read across 240K 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 Cass County Average
Cass County Average
- ●USDA Zones 6a, averaged across Cass County
- ●One soil character for all of Cass County
- ●Frost dates read at Cass County's scale: Apr 2 to Oct 31
YOUR Parcel
- ✓Your exact zone, not Cass County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Cass County
Pull a site-specific report for your exact address in Cass County, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Cass County averages can't show:
We read public map data around Cass County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Cass County average
How we know this about Cass 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 Cass County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Cass County
When does frost risk typically end in Cass County?
The last hard freeze (28°F) in Cass County typically lands around Apr 2, 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 23.
How long is the growing season in Cass County?
Measured between 28°F hard freezes, Cass County sees about 212 frost-free days — roughly Apr 2 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 23 to Oct 17, about 177 days.
Is the soil safe to grow vegetables in Cass County?
The federal record around Cass County shows 127 documented sites, mostly Underground Storage Tanks entries (87), the nearest Brownfields record about 0.5 miles 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.
Everything above is measured at Cass County's scale — its 6a band and its 212-day season. Your yard writes its own version of Cass 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 Cass County’s own scale
9 of the readings below were taken at Cass County's own scale — its own ~212-day span between 28°F freezes, the 3 most extensive soil series mapped here and 127 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Cass County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Cass County's own 28°F hard-freeze dates and its ~212-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Cass CountyUSDA NRCS SSURGO
- 127 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 0.5 miles outFederal environmental registers
- Cass County's boundary and the 240,482 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~212-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Cass County spans, Interior River Valleys and Hills the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Cass County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Cass 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 Cass County — the ~212 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 Cass County's 240,482 acreswhy one lot differs from the next →
- Which of those 127 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 Cass Countyread your own land →