Janesville, Wisconsin, sits in USDA hardiness zone 5b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Among the crops suited to this profile: cabbage, cranberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Janesville, 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 Janesville 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 Janesville — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Janesville — the short answer
Janesville, Wisconsin: USDA zone 5b, about 194 days between hard freezes, across 22K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 12
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 23
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~194
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 22K 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 Janesville's average, not your lot's — a low corner or a tree line moves it. Against Janesville's 194-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Janesville
Each reading below is measured for Janesville itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredJanesville runs about 194 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredJanesville 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 Janesville is in
Janesville sits in the Southeastern Wisconsin Till Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Janesville's own centroid rather than borrowed from Rock County.
What Grows in Janesville
Every plant below cleared Janesville's own zone 5b and its 194-day season. Each card opens that plant's Wisconsin profile. How we score.
Is it too late to plant in Janesville?
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 15; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 12 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 23 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
What's on the federal record near Janesville
Closest first, within ~10 miles of Janesville. Listing isn't leaking, and distance isn't exposure.
- COUNTRYSIDE AUTO BODYBrownfields · 1000 ft
- EMERALD HEIGHTS INC DONALD DUOSSUnderground Storage Tanks · 1800 ft
- Charles StanhopeUnderground Storage Tanks · 1800 ft
- WAYNE R COONUnderground Storage Tanks · 1800 ft
- DALE KEMPUnderground Storage Tanks · 1800 ft
- SELF SID JENSONUnderground Storage Tanks · 1800 ft
- JAMES DEWITT FARMUnderground Storage Tanks · 1800 ft
- Audrey L BarlassUnderground Storage Tanks · 1800 ft
- Bob BladornUnderground Storage Tanks · 1800 ft
- Venable FarmsUnderground Storage Tanks · 1800 ft
- FDW PROPERTIES LTDUnderground Storage Tanks · 1800 ft
- AT&T WisconsinUnderground Storage Tanks · 1900 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Janesville'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 Janesville.
Sources Checked
within ~10 miles of Janesville
Severity Distribution
within ~10 miles of Janesville
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Janesville, Toxics Release Inventory runs higher than the national average — 48 sites within ~10 miles of Janesville. That's not a problem with your land — it's information about it.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Janesville
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 Janesville average
Your land is one point inside Janesville
Everything above resolves to Janesville as a whole — one PHZM band and one 28°F frost record, read across 22K 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 Janesville Average
Janesville Average
- ●USDA Zones 5b, averaged across Janesville
- ●One soil character for all of Janesville
- ●Frost dates read at Janesville's scale: Apr 12 to Oct 23
YOUR Parcel
- ✓Your exact zone, not Janesville's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Janesville
Pull a site-specific report for your exact address in Janesville, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Janesville averages can't show:
We read public map data around Janesville — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Janesville average
How we know this about Janesville
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 Janesville’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 Janesville
When does frost risk typically end in Janesville?
The last hard freeze (28°F) in Janesville typically lands around Apr 12, 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 May 3.
When is the first frost in Janesville?
The first hard freeze (28°F) in Janesville typically arrives around Oct 23, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 9, so the watching starts about Sep 23 — about 194 days after the spring freeze cleared.
How long is the growing season in Janesville?
Measured between 28°F hard freezes, Janesville sees about 194 frost-free days — roughly Apr 12 through Oct 23, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 3 to Oct 9, about 159 days.
Is the soil safe to grow vegetables in Janesville?
The federal record around Janesville runs heavier than most — 686 documented sites, mostly Underground Storage Tanks entries (393), the nearest Brownfields record about 0.2 miles 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 Janesville?
From about Sep 23 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 23 (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 23. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Janesville's scale — its 5b band and its 194-day season. Your yard writes its own version of Janesville'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 Janesville’s own scale
6 of the readings below were taken at Janesville's own scale — its own ~194-day season between 28°F freezes, the 22,171 acres it covers and 686 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Janesville's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Janesville's own 28°F hard-freeze dates, about Apr 12 and Oct 23 and the ~194-day span between themNOAA 1991–2020 Climate Normals
- 686 documented contamination sites on the federal record near Janesville, the closest Brownfields record about 0.2 miles out from the town centreFederal environmental registers
- Janesville's boundary and the 22,171 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~194-day seasonGrowable Ground crop-matching engine
- The ecoregion at Janesville's own centroid, the Southeastern Wisconsin Till PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Janesville's 22,171 acres read through its county's SSURGO summaryfrom Rock County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Rock County
- The growing challenges every Wisconsin grower plans around — written at state scale, so they stay on the state guidefrom Wisconsin
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Rock County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Janesville's 22,171 acreswhy one lot differs from the next →
- Which side of Janesville you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 22,171 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.2 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 Janesville-wide figureread your own land →
More in Wisconsin
Wider growing context
What grows across WisconsinJanesville sits outside our named growing regions, so Wisconsin as a whole is its closest context here.