Colchester, Illinois, sits in USDA hardiness zone 6a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Well-matched crops include cabbage, hazelnut, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Colchester, 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 Colchester 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 Colchester — soil, climate, flood, and parcel records. How we handle your address.
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Colchester — the short answer
Colchester, Illinois: USDA zone 6a, about 211 days between hard freezes, across 736 acres of city.
- 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)
- Oct 31
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~211
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 736 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 Colchester's average, not your lot's — a low corner or a tree line moves it. Against Colchester's 211-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Colchester
Each reading below is measured for Colchester itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredColchester 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
MeasuredColchester 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 Colchester is in
Colchester sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Colchester's own centroid rather than borrowed from McDonough County.
What Grows in Colchester
Every plant below cleared Colchester's own zone 6a and its 211-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Colchester?
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 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 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's on the federal record near Colchester
Closest first, within ~10 miles of Colchester. Listing isn't leaking, and distance isn't exposure.
- Argyle Lake State ParkUnderground Storage Tanks · 150 ft
- SinclairUnderground Storage Tanks · 400 ft
- Colchester City OfUnderground Storage Tanks · 450 ft
- Former Clark #2064Underground Storage Tanks · 550 ft
- Hunt ApplianceUnderground Storage Tanks · 600 ft
- Casey's General Store #2440Underground Storage Tanks · 800 ft
- Colchester Elementary SchoolUnderground Storage Tanks · 850 ft
- COLCHESTER ELEM SCHOOLBrownfields · 850 ft
- Mcdonough Fs IncUnderground Storage Tanks · 1100 ft
- Yetter Mfg CoUnderground Storage Tanks · 1600 ft
- YETTER MANUFACTURING CO INCBrownfields · 1900 ft
- Colchester School District No. 180Underground Storage Tanks · 1900 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Colchester'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 Colchester.
Total Sites
132
within ~10 miles of Colchester
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Colchester
Severity Distribution
within ~10 miles of Colchester
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Colchester, two things run higher than the national average within ~10 miles of Colchester — PFAS (3 sites) and Underground Storage Tanks (84 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Colchester
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 Colchester average
Your land is one point inside Colchester
Everything above resolves to Colchester as a whole — one PHZM band and one 28°F frost record, read across 736 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 city 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 Colchester Average
Colchester Average
- ●USDA Zones 6a, averaged across Colchester
- ●One soil character for all of Colchester
- ●Frost dates read at Colchester's scale: Apr 3 to Oct 31
YOUR Parcel
- ✓Your exact zone, not Colchester's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Colchester
Pull a site-specific report for your exact address in Colchester, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Colchester averages can't show:
We read public map data around Colchester — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Colchester average
How we know this about Colchester
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Colchester’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 city grain anywhere on this page — there is no city-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 Colchester
When does frost risk typically end in Colchester?
The last hard freeze (28°F) in Colchester 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 Colchester?
The first hard freeze (28°F) in Colchester typically arrives around Oct 31, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 17, so the watching starts about Oct 1 — about 211 days after the spring freeze cleared.
How long is the growing season in Colchester?
Measured between 28°F hard freezes, Colchester sees about 211 frost-free days — roughly Apr 3 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 24 to Oct 17, about 176 days.
Is the soil safe to grow vegetables in Colchester?
The federal record around Colchester is a meaningful one — 132 documented sites, mostly Underground Storage Tanks entries (84), the nearest Underground Storage Tanks record under a tenth of a mile out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Colchester?
From about Oct 1 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 Oct 31 (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 Oct 31. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Colchester's scale — its 6a band and its 211-day season. Your yard writes its own version of Colchester'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 Colchester’s own scale
6 of the readings below were taken at Colchester's own scale — its own ~211-day season between 28°F freezes, the 736 acres it covers and 132 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Colchester's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Colchester's own 28°F hard-freeze dates, about Apr 3 and Oct 31 and the ~211-day span between themNOAA 1991–2020 Climate Normals
- 132 documented contamination sites on the federal record near Colchester, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Colchester's boundary and the 736 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~211-day seasonGrowable Ground crop-matching engine
- The ecoregion at Colchester's own centroid, the Interior River Valleys and HillsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Colchester's 736 acres read through its county's SSURGO summaryfrom McDonough County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom McDonough 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 McDonough County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Colchester's 736 acreswhy one lot differs from the next →
- Which side of Colchester you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 736 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Colchester-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisColchester sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides