Ontario, Wisconsin, sits in USDA hardiness zone 4b — a zone band wide enough that plant choice, not possibility, is the interesting question.
A short list that earns its place here — cabbage, cranberry, turkish rocket, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Ontario, 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 Ontario 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 Ontario — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Ontario — the short answer
Ontario, Wisconsin: USDA zone 4b, about 172 days between hard freezes, across 643 acres of town.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 25
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 14
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~172
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 643 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 4b is Ontario's average, not your lot's — a low corner or a tree line moves it. Against Ontario's 172-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Ontario
Each reading below is measured for Ontario itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOntario runs about 172 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
MeasuredOntario sits in USDA hardiness zone 4b.
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 Ontario is in
Ontario sits in the Driftless Area — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Ontario's own centroid rather than borrowed from Vernon County.
What Grows in Ontario
Every plant below cleared Ontario's own zone 4b and its 172-day season. Each card opens that plant's Wisconsin profile. How we score.
Is it too late to plant in Ontario?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 28; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 25 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 14 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
What's on the federal record near Ontario
Closest first, within ~10 miles of Ontario. Listing isn't leaking, and distance isn't exposure.
- DOBBS EXCAVATIONUnderground Storage Tanks · 250 ft
- ARTHUR JOHNSONUnderground Storage Tanks · 250 ft
- FORMER ERNEST SCHULTZ PROPERTYUnderground Storage Tanks · 300 ft
- Wallaces Service StationUnderground Storage Tanks · 300 ft
- STACY DOBBSUnderground Storage Tanks · 400 ft
- VE-14/02W/03-0012Nitrate · 750 ft
- SCHOOL DISTRICT OF ONTARIOUnderground Storage Tanks · 2200 ft
- United CooperativeUnderground Storage Tanks · 2400 ft
- STH 33 EBrownfields · 2400 ft
- Wildcat Mountain State ParkUnderground Storage Tanks · 2500 ft
- JOHN BOLDONUnderground Storage Tanks · 0.5 mi
- VE-14/02W/34-0110Nitrate · 0.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Ontario'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 Ontario.
Total Sites
118
within ~10 miles of Ontario
Risk Level
Moderate
Highest-severity
2 concentrated animal feeding operations
Sources Checked
within ~10 miles of Ontario
Severity Distribution
within ~10 miles of Ontario
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Ontario, two things run higher than the national average within ~10 miles of Ontario — Nitrate (36 sites) and Underground Storage Tanks (74 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Ontario
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 Ontario average
Your land is one point inside Ontario
Everything above resolves to Ontario as a whole — one PHZM band and one 28°F frost record, read across 643 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 Ontario Average
Ontario Average
- ●USDA Zones 4b, averaged across Ontario
- ●One soil character for all of Ontario
- ●Frost dates read at Ontario's scale: Apr 25 to Oct 14
YOUR Parcel
- ✓Your exact zone, not Ontario's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Ontario
Pull a site-specific report for your exact address in Ontario, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Ontario averages can't show:
We read public map data around Ontario — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Ontario average
How we know this about Ontario
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 Ontario’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 Ontario
When does frost risk typically end in Ontario?
The last hard freeze (28°F) in Ontario typically lands around Apr 25, 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 16.
When is the first frost in Ontario?
The first hard freeze (28°F) in Ontario typically arrives around Oct 14, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 30, so the watching starts about Sep 14 — about 172 days after the spring freeze cleared.
How long is the growing season in Ontario?
Measured between 28°F hard freezes, Ontario sees about 172 frost-free days — roughly Apr 25 through Oct 14, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 16 to Sep 30, about 137 days.
Is the soil safe to grow vegetables in Ontario?
The federal record around Ontario shows 118 documented sites, mostly Underground Storage Tanks entries (74), the nearest Underground Storage Tanks record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Ontario?
From about Sep 14 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 14 (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 14. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Ontario's scale — its 4b band and its 172-day season. Your yard writes its own version of Ontario'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 Ontario’s own scale
6 of the readings below were taken at Ontario's own scale — its own ~172-day season between 28°F freezes, the 643 acres it covers and 118 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Ontario's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Ontario's own 28°F hard-freeze dates, about Apr 25 and Oct 14 and the ~172-day span between themNOAA 1991–2020 Climate Normals
- 118 documented contamination sites on the federal record near Ontario, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Ontario's boundary and the 643 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~172-day seasonGrowable Ground crop-matching engine
- The ecoregion at Ontario's own centroid, the Driftless AreaUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Ontario's 643 acres read through its county's SSURGO summaryfrom Vernon County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Vernon 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 Vernon County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Ontario's 643 acreswhy one lot differs from the next →
- Which side of Ontario you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 643 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 Ontario-wide figureread your own land →
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