Washington 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
Washington County holds more than one microclimate.
Soils and elevations shift across Washington 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 Washington County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Washington County — the short answer
Washington County, Illinois: USDA zone 6b, about 226 days between hard freezes, across 360K acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 26
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 7
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~226
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 360K 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 Washington County's average, not your lot's — a low corner or a tree line moves it. Against Washington County's 226-day season, see what your own ground reads.
Heat in Washington County
Across a year, Washington County accumulates about 3,841 growing degree days above 50°F, about 458 more than the middle Illinois county — ahead of 80 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 Washington County
Across Washington County, the ground is predominantly Alfisols, where Hoyleton, Bluford, and Darmstadt are the most extensive named soil series. The soil is generally somewhat poorly drained with a silt loam surface. Topsoil pH runs about 6.0–6.7, slightly acidic. Rainfall drains through hydrologic group C/D soils.
Soil order
Alfisols
Drainage
Somewhat poorly drained
Prime farmland
22%
Hydric soils
16%
Soil still varies lot by lot — soil types explained.
How the ground varies across Washington County
The USDA soil survey maps 61% of Washington County as somewhat poorly drained — but another 38% drains differently: 15% poorly drained, 14% moderately well drained.
Hoyleton is the most extensive named soil at 11% of mapped acres, then Bluford (11%) and Darmstadt (9%).
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 Washington County
Each reading below is measured for Washington 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 Washington County are somewhat poorly drained, in hydrologic group C/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 Washington County runs about pH 6.0–6.7, 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
MeasuredWashington County runs about 226 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
MeasuredWashington County sits in USDA hardiness zone 6b.
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 Washington County is in
Washington 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 Washington County
We scored all 1,086 plants against Washington County's own USDA zone 6b and its own 226-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 Washington County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Feb 26; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 7 — 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 Washington County
- Japanese beetle4 documented records
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Washington County
USGS estimates 280,966 lb of Glyphosate on Washington County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (274,071 lb) and Metolachlor-s (215,241 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 Washington County — and how to grow with it.
We checked the federal record across Washington County — 102 documented sites across 6 of the 9 source types we track.
The most significant on record: 4 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Washington 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 Washington County
Closest first, across Washington County. Listing isn't leaking, and distance isn't exposure.
- American Medical Ser Inc Friendship MnUnderground Storage Tanks · 1.5 mi
- H&J Truck Line IncUnderground Storage Tanks · 1.5 mi
- Washington County Highway DeptUnderground Storage Tanks · 1.7 mi
- IDOTBrownfields · 1.7 mi
- Tim's Tire TimeUnderground Storage Tanks · 1.8 mi
- Washington County Service CompanyUnderground Storage Tanks · 1.9 mi
- Washington County Court HouseUnderground Storage Tanks · 2.0 mi
- Washington County Ser CoUnderground Storage Tanks · 2.0 mi
- Nashville 66Underground Storage Tanks · 2.0 mi
- Washington County CaUnderground Storage Tanks · 2.0 mi
- Kirchoeffer Motor CoUnderground Storage Tanks · 2.0 mi
- Cecil Wetzel Dba Wetzel Oil CoUnderground Storage Tanks · 2.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Washington 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 Washington County.
Total Sites
102
across Washington County
Risk Level
Moderate
Highest-severity
4 Toxics Release Inventory facilities
Sources Checked
across Washington County
Severity Distribution
across Washington County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Washington County, two things run higher than the national average across Washington County — CAFO (8 sites) and Underground Storage Tanks (70 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 Washington 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 Washington County average
Your land is one point inside Washington County
Everything above resolves to Washington County as a whole — one PHZM band and one county frost record, read across 360K 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 Washington County Average
Washington County Average
- ●USDA Zones 6b, averaged across Washington County
- ●One soil character for all of Washington County
- ●Frost dates read at Washington County's scale: Mar 26 to Nov 7
YOUR Parcel
- ✓Your exact zone, not Washington County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Washington County
Pull a site-specific report for your exact address in Washington County, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Washington County averages can't show:
We read public map data around Washington County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Washington County average
How we know this about Washington 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 Washington County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Washington County
When does frost risk typically end in Washington County?
The last hard freeze (28°F) in Washington County typically lands around Mar 26, 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 16.
How long is the growing season in Washington County?
Measured between 28°F hard freezes, Washington County sees about 226 frost-free days — roughly Mar 26 through Nov 7, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 16 to Oct 24, about 191 days.
Is the soil safe to grow vegetables in Washington County?
The federal record around Washington County shows 102 documented sites, mostly Underground Storage Tanks entries (70), the nearest Underground Storage Tanks record about 1.5 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 Washington County's scale — its 6b band and its 226-day season. Your yard writes its own version of Washington 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 Washington County’s own scale
9 of the readings below were taken at Washington County's own scale — its own ~226-day span between 28°F freezes, the 3 most extensive soil series mapped here and 102 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Washington County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Washington County's own 28°F hard-freeze dates and its ~226-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Washington CountyUSDA NRCS SSURGO
- 102 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.5 miles outFederal environmental registers
- Washington County's boundary and the 360,062 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~226-day seasonGrowable Ground crop-matching engine
- Washington County sitting wholly inside the Interior River Valleys and HillsUS EPA Level III Ecoregions
- Open occurrence records documented in Washington County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Washington 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 Washington County — the ~226 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 Washington County's 360,062 acreswhy one lot differs from the next →
- Which of those 102 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 Washington Countyread your own land →