Brown County, in Illinois, sits in USDA hardiness zone 6a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Crops well matched to these conditions include cabbage, hazelnut, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Brown County holds more than one microclimate.
Soils and elevations shift across Brown 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 Brown County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Brown County — the short answer
Brown County, Illinois: USDA zone 6a, about 213 days between hard freezes, across 196K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 1
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 31
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~213
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 196K 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 Brown County's average, not your lot's — a low corner or a tree line moves it. Against Brown County's 213-day season, see what your own ground reads.
Heat in Brown County
Across a year, Brown County accumulates about 3,317 growing degree days above 50°F, about 66 fewer than the middle Illinois county — ahead of 43 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 Brown County
Across Brown County, the ground is predominantly Alfisols, where Hickory, Rozetta, and Fayette are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.0–6.8, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
22%
Hydric soils
7%
Soil still varies lot by lot — soil types explained.
How the ground varies across Brown County
The USDA soil survey maps 63% of Brown County as well drained — but another 36% drains differently: 26% somewhat poorly drained, 7% poorly drained.
Hickory is the most extensive named soil at 16% of mapped acres, then Rozetta (14%) and Fayette (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 Brown County
Each reading below is measured for Brown 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 Brown 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 Brown County runs about pH 6.0–6.8, 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
Season length
MeasuredBrown County runs about 213 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
MeasuredBrown 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 Brown County is in
Brown 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 Brown County
We scored all 1,086 plants against Brown County's own USDA zone 6a and its own 213-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 Brown 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 Mar 4; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 1 (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.
What gets applied to farmland in Brown County
USGS estimates 67,248 lb of Glyphosate on Brown County farmland in 2019, its largest by weight, ahead of Atrazine (26,290 lb) and Acetochlor (23,894 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 Brown County — and how to grow with it.
We checked the federal record across Brown County — 47 documented sites across 4 of the 9 source types we track.
The most significant on record: 11 brownfield sites. Former commercial or industrial land where legacy contamination may persist.
The federal record across Brown 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 Brown County
Closest first, across Brown County. Listing isn't leaking, and distance isn't exposure.
- WESTERN ILLINOIS CORRECTIONAL CENTERBrownfields · 1400 ft
- Ron Tire SerUnderground Storage Tanks · 1.0 mi
- ILDOT DIST 6Brownfields · 1.3 mi
- DOLLAR GENERAL STORE 1110Brownfields · 1.5 mi
- E M S SunocoUnderground Storage Tanks · 1.5 mi
- Mt. Sterling ConocoUnderground Storage Tanks · 1.6 mi
- Mount Sterling Elevator Co IncUnderground Storage Tanks · 1.6 mi
- Mount Sterling Implement CoUnderground Storage Tanks · 1.6 mi
- Casey's General Store #3256Underground Storage Tanks · 1.6 mi
- Schuyler Brown Fs., Inc.Underground Storage Tanks · 1.6 mi
- WESTERN GRAIN MARKETING LLCBrownfields · 1.6 mi
- Brown County Hwy DeptUnderground Storage Tanks · 1.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Brown 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 Brown County.
Sources Checked
across Brown County
Severity Distribution
across Brown County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Brown County, Underground Storage Tanks runs higher than the national average — 31 sites across Brown 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 Brown 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 Brown County average
Your land is one point inside Brown County
Everything above resolves to Brown County as a whole — one PHZM band and one county frost record, read across 196K 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 Brown County Average
Brown County Average
- ●USDA Zones 6a, averaged across Brown County
- ●One soil character for all of Brown County
- ●Frost dates read at Brown County's scale: Apr 1 to Oct 31
YOUR Parcel
- ✓Your exact zone, not Brown County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Brown County
Pull a site-specific report for your exact address in Brown County, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Brown County averages can't show:
We read public map data around Brown County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Brown County average
How we know this about Brown 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 Brown County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Brown County
When does frost risk typically end in Brown County?
The last hard freeze (28°F) in Brown County typically lands around Apr 1, 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 22.
How long is the growing season in Brown County?
Measured between 28°F hard freezes, Brown County sees about 213 frost-free days — roughly Apr 1 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 22 to Oct 17, about 178 days.
Is the soil safe to grow vegetables in Brown County?
The federal record around Brown County is light — 47 documented sites across the 9 federal source types we checked, mostly Underground Storage Tanks entries (31), the nearest Brownfields record about 0.3 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 Brown County's scale — its 6a band and its 213-day season. Your yard writes its own version of Brown 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 Brown County’s own scale
8 of the readings below were taken at Brown County's own scale — its own ~213-day span between 28°F freezes, the 3 most extensive soil series mapped here and 47 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Brown County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Brown County's own 28°F hard-freeze dates and its ~213-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Brown CountyUSDA NRCS SSURGO
- 47 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 0.3 miles outFederal environmental registers
- Brown County's boundary and the 195,665 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~213-day seasonGrowable Ground crop-matching engine
- Brown County sitting wholly inside the Interior River Valleys and HillsUS EPA Level III Ecoregions
- Which agricultural compounds go onto Brown 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 Brown County — the ~213 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 Brown County's 195,665 acreswhy one lot differs from the next →
- Which of those 47 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 Brown Countyread your own land →