Diamond, Illinois, sits in USDA hardiness zone 5b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Crops well matched to these conditions include cabbage, blueberry, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Diamond, 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 Diamond 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 Diamond — soil, climate, flood, and parcel records. How we handle your address.
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Diamond — the short answer
Diamond, Illinois: USDA zone 5b, about 205 days between hard freezes, across 1K acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 9
- 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
- ~205
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 1K 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 5b is Diamond's average, not your lot's — a low corner or a tree line moves it. Against Diamond's 205-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Diamond
Each reading below is measured for Diamond itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredDiamond runs about 205 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
MeasuredDiamond sits in USDA hardiness zone 5b.
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 Diamond is in
Diamond sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Diamond's own centroid rather than borrowed from Grundy County.
What Grows in Diamond
Every plant below cleared Diamond's own zone 5b and its 205-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Diamond?
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 12; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 9 (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. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
Documented around Diamond
Spotted lanternfly documented 30 miles from Diamond, first recorded 2023. What to watch for.
What's on the federal record near Diamond
Closest first, within ~10 miles of Diamond. Listing isn't leaking, and distance isn't exposure.
- JEWEL 3745Brownfields · 1500 ft
- CASEYS GENERAL STORE 1981Brownfields · 1900 ft
- Casey's General Store #1981Underground Storage Tanks · 1900 ft
- COAL CITY COB CO INC - COAL CBrownfields · 0.7 mi
- Diamond Minit Mart #610Underground Storage Tanks · 0.8 mi
- Mac's #1205Underground Storage Tanks · 0.9 mi
- WARRENS COLLISION CENTERBrownfields · 1.0 mi
- AUTO TEK SPECIALTY INCBrownfields · 1.2 mi
- Coal City Minit MartUnderground Storage Tanks · 1.3 mi
- QUALITY AUTO BODYBrownfields · 1.3 mi
- SECOND TIME AROUND ANTIQUE MKTBrownfields · 1.4 mi
- CHICAGO AEROSOL, LLCToxics Release Inventory · 1.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Diamond'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 Diamond.
Sources Checked
within ~10 miles of Diamond
Severity Distribution
within ~10 miles of Diamond
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Diamond, two things run higher than the national average within ~10 miles of Diamond — Superfund (7 sites) and PFAS (4 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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 Diamond
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 Diamond average
Your land is one point inside Diamond
Everything above resolves to Diamond as a whole — one PHZM band and one 28°F frost record, read across 1K 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 Diamond Average
Diamond Average
- ●USDA Zones 5b, averaged across Diamond
- ●One soil character for all of Diamond
- ●Frost dates read at Diamond's scale: Apr 9 to Oct 31
YOUR Parcel
- ✓Your exact zone, not Diamond's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Diamond
Pull a site-specific report for your exact address in Diamond, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Diamond averages can't show:
We read public map data around Diamond — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Diamond average
How we know this about Diamond
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 Diamond’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 Diamond
When does frost risk typically end in Diamond?
The last hard freeze (28°F) in Diamond typically lands around Apr 9, 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 30.
When is the first frost in Diamond?
The first hard freeze (28°F) in Diamond 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 205 days after the spring freeze cleared.
How long is the growing season in Diamond?
Measured between 28°F hard freezes, Diamond sees about 205 frost-free days — roughly Apr 9 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 30 to Oct 17, about 170 days.
Is the soil safe to grow vegetables in Diamond?
The federal record around Diamond is a meaningful one — 245 documented sites, mostly Underground Storage Tanks entries (117), the nearest Brownfields record about 0.3 miles 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 Diamond?
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 Diamond's scale — its 5b band and its 205-day season. Your yard writes its own version of Diamond'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 Diamond’s own scale
7 of the readings below were taken at Diamond's own scale — its own ~205-day season between 28°F freezes, the 1,216 acres it covers and 245 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Diamond's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Diamond's own 28°F hard-freeze dates, about Apr 9 and Oct 31 and the ~205-day span between themNOAA 1991–2020 Climate Normals
- 245 documented contamination sites on the federal record near Diamond, the closest Brownfields record about 0.3 miles out from the town centreFederal environmental registers
- Diamond's boundary and the 1,216 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~205-day seasonGrowable Ground crop-matching engine
- The ecoregion at Diamond's own centroid, the Central Corn Belt PlainsUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of Diamondlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Diamond's 1,216 acres read through its county's SSURGO summaryfrom Grundy County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Grundy 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 Grundy County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Diamond's 1,216 acreswhy one lot differs from the next →
- Which side of Diamond you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,216 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.3 miles 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 Diamond-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisDiamond sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides