Belknap, Illinois, sits in USDA hardiness zone 7a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
The conditions favor cabbage, hazelnut, california poppy, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Belknap, 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 Belknap 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 Belknap — soil, climate, flood, and parcel records. How we handle your address.
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Belknap — the short answer
Belknap, Illinois: USDA zone 7a, about 240 days between hard freezes, across 677 acres of town.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 20
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 15
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~240
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 677 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 7a is Belknap's average, not your lot's — a low corner or a tree line moves it. Against Belknap's 240-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Belknap
Each reading below is measured for Belknap itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredBelknap runs about 240 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
MeasuredBelknap sits in USDA hardiness zone 7a.
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 Belknap is in
Belknap sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Belknap's own centroid, and it is not what its county reads: Johnson County is mostly Interior Plateau. The wider page above you is answering a different question about different ground.
What Grows in Belknap
Every plant below cleared Belknap's own zone 7a and its 240-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Belknap?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Feb 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 20 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 15 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
What's on the federal record near Belknap
Closest first, within ~10 miles of Belknap. Listing isn't leaking, and distance isn't exposure.
- 14S 2E- 1.Nitrate · 700 ft
- Hodge J CUnderground Storage Tanks · 2300 ft
- Il Dept Of ConservationUnderground Storage Tanks · 2300 ft
- Corzine Feed MillUnderground Storage Tanks · 2.5 mi
- Storage FacilityUnderground Storage Tanks · 2.7 mi
- Tapley Service StationUnderground Storage Tanks · 2.8 mi
- MARTIN BROTHERS CONTAINERSSuperfund · 3.5 mi
- Kiefers GarageUnderground Storage Tanks · 3.7 mi
- Cypress Plant-Vulcan Material Co.Underground Storage Tanks · 4.5 mi
- Roach 76Underground Storage Tanks · 4.7 mi
- K-J'sUnderground Storage Tanks · 5.2 mi
- Clark 76Underground Storage Tanks · 5.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Belknap'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 Belknap.
Total Sites
69
within ~10 miles of Belknap
Risk Level
Elevated
Highest-severity
2 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Belknap
Severity Distribution
within ~10 miles of Belknap
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
Check your specific parcel in Belknap
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 Belknap average
Your land is one point inside Belknap
Everything above resolves to Belknap as a whole — one PHZM band and one 28°F frost record, read across 677 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 Belknap Average
Belknap Average
- ●USDA Zones 7a, averaged across Belknap
- ●One soil character for all of Belknap
- ●Frost dates read at Belknap's scale: Mar 20 to Nov 15
YOUR Parcel
- ✓Your exact zone, not Belknap's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Belknap
Pull a site-specific report for your exact address in Belknap, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Belknap averages can't show:
We read public map data around Belknap — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Belknap average
How we know this about Belknap
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 Belknap’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 Belknap
When does frost risk typically end in Belknap?
The last hard freeze (28°F) in Belknap typically lands around Mar 20, 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 10.
When is the first frost in Belknap?
The first hard freeze (28°F) in Belknap typically arrives around Nov 15, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 1, so the watching starts about Oct 16 — about 240 days after the spring freeze cleared.
How long is the growing season in Belknap?
Measured between 28°F hard freezes, Belknap sees about 240 frost-free days — roughly Mar 20 through Nov 15, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 10 to Nov 1, about 205 days.
Is the soil safe to grow vegetables in Belknap?
The federal record around Belknap is a meaningful one — 69 documented sites, mostly Underground Storage Tanks entries (41), the nearest Nitrate record about 0.1 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 Belknap?
From about Oct 16 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 15 (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 15. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Belknap's scale — its 7a band and its 240-day season. Your yard writes its own version of Belknap'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 Belknap’s own scale
6 of the readings below were taken at Belknap's own scale — its own ~240-day season between 28°F freezes, the 677 acres it covers and 69 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Belknap's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Belknap's own 28°F hard-freeze dates, about Mar 20 and Nov 15 and the ~240-day span between themNOAA 1991–2020 Climate Normals
- 69 documented contamination sites on the federal record near Belknap, the closest Nitrate record about 0.1 miles out from the town centreFederal environmental registers
- Belknap's boundary and the 677 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~240-day seasonGrowable Ground crop-matching engine
- Belknap sits in the Interior River Valleys and Hills — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Belknap's 677 acres read through its county's SSURGO summaryfrom Johnson County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Johnson 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 Johnson County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Belknap's 677 acreswhy one lot differs from the next →
- Which side of Belknap you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 677 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.1 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 Belknap-wide figureread your own land →