Cobb, Wisconsin, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Crops well matched to these conditions include cabbage, cranberry, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Cobb, 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 Cobb 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 Cobb — soil, climate, flood, and parcel records. How we handle your address.
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Cobb — the short answer
Cobb, Wisconsin: USDA zone 5a, about 191 days between hard freezes, across 658 acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 14
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~191
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 658 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 Cobb's average, not your lot's — a low corner or a tree line moves it. Against Cobb's 191-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Cobb
Each reading below is measured for Cobb itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCobb runs about 191 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
MeasuredCobb 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 Cobb is in
Cobb sits in the Driftless Area — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Cobb's own centroid rather than borrowed from Iowa County.
What Grows in Cobb
Every plant below cleared Cobb's own zone 5a and its 191-day season. Each card opens that plant's Wisconsin profile. How we score.
Is it too late to plant in Cobb?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 17; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 14 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 22 — 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 Cobb
Closest first, within ~10 miles of Cobb. Listing isn't leaking, and distance isn't exposure.
- Fingersons ServiceUnderground Storage Tanks · 500 ft
- STOKELY USA INCUnderground Storage Tanks · 550 ft
- Merlin FritchUnderground Storage Tanks · 600 ft
- IOWA LAFAYETTE FSUnderground Storage Tanks · 600 ft
- TOWN OF EDENUnderground Storage Tanks · 600 ft
- IW-06/01E/25-0005Nitrate · 600 ft
- Village Of Cobb Wastewater Treatment PlantUnderground Storage Tanks · 600 ft
- GOLDSMITHS FEEDUnderground Storage Tanks · 1000 ft
- IW-06/01E/26-0049Nitrate · 1100 ft
- DOLLAR GENERAL #21868Brownfields · 1200 ft
- Cobb Food MartUnderground Storage Tanks · 1800 ft
- Ritchie Motors IncUnderground Storage Tanks · 1900 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Cobb'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 Cobb.
Sources Checked
within ~10 miles of Cobb
Severity Distribution
within ~10 miles of Cobb
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Cobb, Mining runs higher than the national average — 344 sites within ~10 miles of Cobb. 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.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Cobb
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 Cobb average
Your land is one point inside Cobb
Everything above resolves to Cobb as a whole — one PHZM band and one 28°F frost record, read across 658 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 Cobb Average
Cobb Average
- ●USDA Zones 5a, averaged across Cobb
- ●One soil character for all of Cobb
- ●Frost dates read at Cobb's scale: Apr 14 to Oct 22
YOUR Parcel
- ✓Your exact zone, not Cobb's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Cobb
Pull a site-specific report for your exact address in Cobb, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Cobb averages can't show:
We read public map data around Cobb — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Cobb average
How we know this about Cobb
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 Cobb’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 Cobb
When does frost risk typically end in Cobb?
The last hard freeze (28°F) in Cobb typically lands around Apr 14, 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 5.
When is the first frost in Cobb?
The first hard freeze (28°F) in Cobb typically arrives around Oct 22, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 8, so the watching starts about Sep 22 — about 191 days after the spring freeze cleared.
How long is the growing season in Cobb?
Measured between 28°F hard freezes, Cobb sees about 191 frost-free days — roughly Apr 14 through Oct 22, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 5 to Oct 8, about 156 days.
Is the soil safe to grow vegetables in Cobb?
The federal record around Cobb runs heavier than most — 511 documented sites, mostly Mining entries (344), the nearest Underground Storage Tanks record under a tenth of a mile 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 Cobb?
From about Sep 22 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 22 (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 22. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Cobb's scale — its 5a band and its 191-day season. Your yard writes its own version of Cobb'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 Cobb’s own scale
6 of the readings below were taken at Cobb's own scale — its own ~191-day season between 28°F freezes, the 658 acres it covers and 511 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Cobb's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Cobb's own 28°F hard-freeze dates, about Apr 14 and Oct 22 and the ~191-day span between themNOAA 1991–2020 Climate Normals
- 511 documented contamination sites on the federal record near Cobb, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Cobb's boundary and the 658 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~191-day seasonGrowable Ground crop-matching engine
- The ecoregion at Cobb's own centroid, the Driftless AreaUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Cobb's 658 acres read through its county's SSURGO summaryfrom Iowa County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Iowa 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 Iowa County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Cobb's 658 acreswhy one lot differs from the next →
- Which side of Cobb you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 658 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 Cobb-wide figureread your own land →
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