Piatt 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
Piatt County holds more than one microclimate.
Soils and elevations shift across Piatt 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 Piatt County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Piatt County — the short answer
Piatt County, Illinois: USDA zone 6a, about 211 days between hard freezes, across 281K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 4
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 1
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~211
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 281K 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 Piatt County's average, not your lot's — a low corner or a tree line moves it. Against Piatt County's 211-day season, see what your own ground reads.
Heat in Piatt County
Across a year, Piatt County accumulates about 3,288 growing degree days above 50°F, about 95 fewer than the middle Illinois county — ahead of 42 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 Piatt County
Across Piatt County, the ground is predominantly Mollisols, where Drummer, Flanagan, and Sable are the most extensive named soil series. The soil is generally poorly drained with a silty clay loam surface. Topsoil pH runs about 6.1–6.7, slightly acidic. Rainfall drains through hydrologic group B/D soils.
Soil order
Mollisols
Drainage
Poorly drained
Prime farmland
45%
Hydric soils
49%
Soil still varies lot by lot — soil types explained.
How the ground varies across Piatt County
The USDA soil survey maps 49% of Piatt County as poorly drained — but another 51% drains differently: 36% somewhat poorly drained, 9% moderately well drained.
Drummer is the most extensive named soil at 23% of mapped acres, then Flanagan (21%) and Sable (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 Piatt County
Each reading below is measured for Piatt 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 Piatt County are poorly drained, in hydrologic group B/D — ground that sheds water slowly.
Beds can stay saturated for days after heavy rain, and the roots of most vegetables, berries, and fruit trees suffocate or rot in soil that never drains.
Raised beds or mounded rows lift roots above the wet zone; choose water-tolerant crops for the lowest spots.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Piatt County runs about pH 6.1–6.7, 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
Season length
MeasuredPiatt County 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
MeasuredPiatt County 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 Piatt County is in
Piatt County sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. One consistent ecological setting across the whole county.
What Grows in Piatt County
We scored all 1,086 plants against Piatt County's own USDA zone 6a and its own 211-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 Piatt County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 7; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 1 — 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 Piatt County
- monarch butterfly14 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Piatt County
USGS estimates 233,568 lb of Glyphosate on Piatt County farmland in 2019, its largest by weight, ahead of Acetochlor (104,747 lb) and Atrazine (89,130 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 Piatt County — and how to grow with it.
We checked the federal record across Piatt County — 145 documented sites across 5 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 Piatt 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 Piatt County
Closest first, across Piatt County. Listing isn't leaking, and distance isn't exposure.
- GENERAL CABLEToxics Release Inventory · 1.0 mi
- GENERAL CABLEBrownfields · 1.0 mi
- ADVANCED DRAINAGE SYSTEMSBrownfields · 1.1 mi
- Cargill Hybrid SeedsUnderground Storage Tanks · 1.1 mi
- Advanced Drainage Systems IncUnderground Storage Tanks · 1.1 mi
- HEACOCK INCBrownfields · 1.2 mi
- New Washington SchoolUnderground Storage Tanks · 1.3 mi
- Piatt County Service CompanyUnderground Storage Tanks · 1.3 mi
- Monticello Grain CoUnderground Storage Tanks · 1.3 mi
- Monticello High SchoolUnderground Storage Tanks · 1.4 mi
- Fruendt David OUnderground Storage Tanks · 1.4 mi
- Casey's General Store #2363Underground Storage Tanks · 1.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Piatt 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 Piatt County.
Total Sites
145
across Piatt County
Risk Level
Moderate
Highest-severity
3 Toxics Release Inventory facilities
Sources Checked
across Piatt County
Severity Distribution
across Piatt County
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
Check your specific parcel in Piatt 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 Piatt County average
Your land is one point inside Piatt County
Everything above resolves to Piatt County as a whole — one PHZM band and one county frost record, read across 281K 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 Piatt County Average
Piatt County Average
- ●USDA Zones 6a, averaged across Piatt County
- ●One soil character for all of Piatt County
- ●Frost dates read at Piatt County's scale: Apr 4 to Nov 1
YOUR Parcel
- ✓Your exact zone, not Piatt County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Piatt County
Pull a site-specific report for your exact address in Piatt County, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Piatt County averages can't show:
We read public map data around Piatt County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Piatt County average
How we know this about Piatt 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 Piatt County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Piatt County
When does frost risk typically end in Piatt County?
The last hard freeze (28°F) in Piatt County typically lands around Apr 4, 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 25.
How long is the growing season in Piatt County?
Measured between 28°F hard freezes, Piatt County sees about 211 frost-free days — roughly Apr 4 through Nov 1, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 25 to Oct 18, about 176 days.
Is the soil safe to grow vegetables in Piatt County?
The federal record around Piatt County shows 145 documented sites, mostly Underground Storage Tanks entries (85), the nearest Toxics Release Inventory record about 1.0 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 Piatt County's scale — its 6a band and its 211-day season. Your yard writes its own version of Piatt 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 Piatt County’s own scale
9 of the readings below were taken at Piatt County's own scale — its own ~211-day span between 28°F freezes, the 3 most extensive soil series mapped here and 145 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Piatt County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Piatt County's own 28°F hard-freeze dates and its ~211-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Piatt CountyUSDA NRCS SSURGO
- 145 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Toxics Release Inventory record about 1.0 miles outFederal environmental registers
- Piatt County's boundary and the 281,080 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~211-day seasonGrowable Ground crop-matching engine
- Piatt County sitting wholly inside the Central Corn Belt PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Piatt County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Piatt 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 Piatt County — the ~211 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 Piatt County's 281,080 acreswhy one lot differs from the next →
- Which of those 145 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 Piatt Countyread your own land →