Potosi, Wisconsin, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Potosi, 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 Potosi 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 Potosi — soil, climate, flood, and parcel records. How we handle your address.
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Potosi — the short answer
Potosi, Wisconsin: USDA zone 5a, about 202 days between hard freezes, across 1K acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 8
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 27
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~202
- 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 5a is Potosi's average, not your lot's — a low corner or a tree line moves it. Against Potosi's 202-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Potosi
Each reading below is measured for Potosi itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPotosi runs about 202 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
MeasuredPotosi sits in USDA hardiness zone 5a.
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 Potosi is in
Potosi sits in the Driftless Area — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Potosi's own centroid rather than borrowed from Grant County.
What Grows in Potosi
Every plant below cleared Potosi's own zone 5a and its 202-day season. Each card opens that plant's Wisconsin profile. How we score.
Is it too late to plant in Potosi?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 11; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 8 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 27 — 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 Potosi
Closest first, within ~10 miles of Potosi. Listing isn't leaking, and distance isn't exposure.
- DAVID LUMBER INCUnderground Storage Tanks · 1600 ft
- Cardiff No. 2 MineMining · 1800 ft
- Potosi Pine Point LLCUnderground Storage Tanks · 1900 ft
- SPORTSMANS SHACKUnderground Storage Tanks · 2000 ft
- GR-03/03W/34-0024Nitrate · 2100 ft
- GR-03/03W/35-0045Nitrate · 2200 ft
- REYNOLDS IOCOUnderground Storage Tanks · 0.7 mi
- Town Of PotosiUnderground Storage Tanks · 0.8 mi
- Long Range Lead DiggingsMining · 0.8 mi
- IOCO SPEEDE SHOPPEUnderground Storage Tanks · 0.9 mi
- THE ROADHOUSEUnderground Storage Tanks · 0.9 mi
- ST ANDREW THOMAS SCHOOLBrownfields · 0.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Potosi'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 Potosi.
Total Sites
156
within ~10 miles of Potosi
Risk Level
High
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Potosi
Severity Distribution
within ~10 miles of Potosi
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Potosi, two things run higher than the national average within ~10 miles of Potosi — Mining (46 sites) and CAFO (4 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Check your specific parcel in Potosi
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 Potosi average
Your land is one point inside Potosi
Everything above resolves to Potosi 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 Potosi Average
Potosi Average
- ●USDA Zones 5a, averaged across Potosi
- ●One soil character for all of Potosi
- ●Frost dates read at Potosi's scale: Apr 8 to Oct 27
YOUR Parcel
- ✓Your exact zone, not Potosi's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Potosi
Pull a site-specific report for your exact address in Potosi, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Potosi averages can't show:
We read public map data around Potosi — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Potosi average
How we know this about Potosi
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 Potosi’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 Potosi
When does frost risk typically end in Potosi?
The last hard freeze (28°F) in Potosi typically lands around Apr 8, 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 29.
When is the first frost in Potosi?
The first hard freeze (28°F) in Potosi typically arrives around Oct 27, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 13, so the watching starts about Sep 27 — about 202 days after the spring freeze cleared.
How long is the growing season in Potosi?
Measured between 28°F hard freezes, Potosi sees about 202 frost-free days — roughly Apr 8 through Oct 27, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 29 to Oct 13, about 167 days.
Is the soil safe to grow vegetables in Potosi?
The federal record around Potosi runs heavier than most — 156 documented sites, mostly Underground Storage Tanks entries (68), the nearest Underground Storage Tanks record about 0.3 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 Potosi?
From about Sep 27 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 27 (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 27. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Potosi's scale — its 5a band and its 202-day season. Your yard writes its own version of Potosi'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 Potosi’s own scale
6 of the readings below were taken at Potosi's own scale — its own ~202-day season between 28°F freezes, the 1,062 acres it covers and 156 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Potosi's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Potosi's own 28°F hard-freeze dates, about Apr 8 and Oct 27 and the ~202-day span between themNOAA 1991–2020 Climate Normals
- 156 documented contamination sites on the federal record near Potosi, the closest Underground Storage Tanks record about 0.3 miles out from the town centreFederal environmental registers
- Potosi's boundary and the 1,062 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~202-day seasonGrowable Ground crop-matching engine
- The ecoregion at Potosi's own centroid, the Driftless AreaUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Potosi's 1,062 acres read through its county's SSURGO summaryfrom Grant County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Grant 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 Grant County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Potosi's 1,062 acreswhy one lot differs from the next →
- Which side of Potosi you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,062 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Potosi-wide figureread your own land →
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