Posen, Illinois, sits in USDA hardiness zone 6a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Among the crops suited to this profile: cabbage, blueberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Posen, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Posen lot. 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 Posen — soil, climate, flood, and parcel records. How we handle your address.
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Posen — the short answer
Posen, Illinois: USDA zone 6a, about 220 days between hard freezes, across 748 acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 9
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~220
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 748 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 Posen's average, not your lot's — a low corner or a tree line moves it. Against Posen's 220-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Posen
Each reading below is measured for Posen itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPosen runs about 220 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
MeasuredPosen 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 Posen is in
Posen sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Posen's own centroid rather than borrowed from Cook County.
What Grows in Posen
Every plant below cleared Posen's own zone 6a and its 220-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Posen?
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 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 9 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
Documented around Posen
Spotted lanternfly documented 6 miles from Posen, first recorded 2023. What to watch for.
What's on the federal record near Posen
Closest first, within ~10 miles of Posen. Listing isn't leaking, and distance isn't exposure.
- POSENPFAS · 200 ft
- Posen Gas & FoodUnderground Storage Tanks · 1100 ft
- OOSTERBAAN & SONSBrownfields · 1300 ft
- Custom Plate Glass Inc.Underground Storage Tanks · 1500 ft
- Montgomery WardUnderground Storage Tanks · 1500 ft
- MONTGOMERY WARDSBrownfields · 1500 ft
- Oosterbaan & Sons CoUnderground Storage Tanks · 1600 ft
- Benjamin E Sherman & SonsUnderground Storage Tanks · 1700 ft
- KIEWIT WESTERNBrownfields · 2100 ft
- Future EnvironmentalUnderground Storage Tanks · 2400 ft
- GFL ENV SERVICES USA LLCBrownfields · 2400 ft
- AUTOMOTIVE DESIGN CENTER INCBrownfields · 2500 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Posen'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 Posen.
Sources Checked
within ~10 miles of Posen
Severity Distribution
within ~10 miles of Posen
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Posen, two things run higher than the national average within ~10 miles of Posen — Superfund (79 sites) and PFAS (42 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Superfund: Superfund sites represent the most severe contamination in the federal system.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check your specific parcel in Posen
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 Posen average
Your land is one point inside Posen
Everything above resolves to Posen as a whole — one PHZM band and one 28°F frost record, read across 748 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 town 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 local average.
Your Lot vs the Posen Average
Posen Average
- ●USDA Zones 6a, averaged across Posen
- ●One soil character for all of Posen
- ●Frost dates read at Posen's scale: Apr 3 to Nov 9
YOUR Parcel
- ✓Your exact zone, not Posen's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Posen
Pull a site-specific report for your exact address in Posen, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Posen averages can't show:
We read public map data around Posen — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Posen average
How we know this about Posen
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Posen’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Posen
When does frost risk typically end in Posen?
The last hard freeze (28°F) in Posen typically lands around Apr 3, 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 24.
When is the first frost in Posen?
The first hard freeze (28°F) in Posen typically arrives around Nov 9, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 26, so the watching starts about Oct 10 — about 220 days after the spring freeze cleared.
How long is the growing season in Posen?
Measured between 28°F hard freezes, Posen sees about 220 frost-free days — roughly Apr 3 through Nov 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 24 to Oct 26, about 185 days.
Is the soil safe to grow vegetables in Posen?
The federal record around Posen runs heavier than most — 3,801 documented sites, mostly Underground Storage Tanks entries (1,974), the nearest PFAS record under a tenth of a mile out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do I protect my plants from frost in Posen?
From about Oct 10 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Nov 9 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Nov 9. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Posen's scale — its 6a band and its 220-day season. Your yard writes its own version of Posen's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Posen’s own scale
7 of the readings below were taken at Posen's own scale — its own ~220-day season between 28°F freezes, the 748 acres it covers and 3,801 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Posen's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Posen's own 28°F hard-freeze dates, about Apr 3 and Nov 9 and the ~220-day span between themNOAA 1991–2020 Climate Normals
- 3,801 documented contamination sites on the federal record near Posen, the closest PFAS record under a tenth of a mile out from the town centreFederal environmental registers
- Posen's boundary and the 748 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~220-day seasonGrowable Ground crop-matching engine
- The ecoregion at Posen's own centroid, the Central Corn Belt PlainsUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of Posenlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Posen's 748 acres read through its county's SSURGO summaryfrom Cook County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Cook County
- The growing challenges every Illinois grower plans around — written at state scale, so they stay on the state guidefrom Illinois
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Cook County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Posen's 748 acreswhy one lot differs from the next →
- Which side of Posen you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 748 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest PFAS record under a tenth of a mile out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Posen-wide figureread your own land →
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