Mercer, Wisconsin, sits in USDA hardiness zone 4a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Expect cabbage, cranberry, cilantro, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Mercer, 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 Mercer 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 Mercer — soil, climate, flood, and parcel records. How we handle your address.
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Mercer — the short answer
Mercer, Wisconsin: USDA zone 4a, about 148 days between hard freezes, across 3K acres of town.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 9
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 4
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~148
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 3K 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 4a is Mercer's average, not your lot's — a low corner or a tree line moves it. Against Mercer's 148-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Mercer
Each reading below is measured for Mercer itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredMercer runs about 148 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredMercer sits in USDA hardiness zone 4a.
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 Mercer is in
Mercer sits in the Northern Lakes and Forests — EPA Level III, inside the wider Northern Forests. That is read at Mercer's own centroid rather than borrowed from Iron County.
What Grows in Mercer
Every plant below cleared Mercer's own zone 4a and its 148-day season. Each card opens that plant's Wisconsin profile. How we score.
Is it too late to plant in Mercer?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Apr 11; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 9 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 4 — long-season crops need about 90 days of runway, quick greens only 30. Even here the calendar’s edges hold value: thirty-day greens late in the window, then garlic and a rested bed for spring.
What's on the federal record near Mercer
Closest first, within ~10 miles of Mercer. Listing isn't leaking, and distance isn't exposure.
- SIMPSON ELECTRIC COBrownfields · 2100 ft
- IR-43/04E/31-0085Nitrate · 0.5 mi
- FAMILY HEALTH CENTER OF MARSHFIELD, INC. MERCER CENTERBrownfields · 0.6 mi
- SKINNERS MARINEUnderground Storage Tanks · 0.7 mi
- MERCER SHELLUnderground Storage Tanks · 0.7 mi
- CAL ENTERPRISESUnderground Storage Tanks · 0.7 mi
- RICHARTS MINI MARTUnderground Storage Tanks · 0.7 mi
- ACTION FLOOR SYSTEMS LLCBrownfields · 0.7 mi
- T-BIRD READY MIXBrownfields · 0.9 mi
- NORTHERN LAKES CONCRETEUnderground Storage Tanks · 0.9 mi
- Action Floor Systems LLCUnderground Storage Tanks · 0.9 mi
- Krist Food Mart #70Underground Storage Tanks · 1.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mercer'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 Mercer.
Sources Checked
within ~10 miles of Mercer
Severity Distribution
within ~10 miles of Mercer
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Mercer, Underground Storage Tanks runs higher than the national average — 77 sites within ~10 miles of Mercer. That's not a problem with your land — it's information about it.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Mercer
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 Mercer average
Your land is one point inside Mercer
Everything above resolves to Mercer as a whole — one PHZM band and one 28°F frost record, read across 3K 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 Mercer Average
Mercer Average
- ●USDA Zones 4a, averaged across Mercer
- ●One soil character for all of Mercer
- ●Frost dates read at Mercer's scale: May 9 to Oct 4
YOUR Parcel
- ✓Your exact zone, not Mercer's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Mercer
Pull a site-specific report for your exact address in Mercer, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mercer averages can't show:
We read public map data around Mercer — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mercer average
How we know this about Mercer
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 Mercer’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 Mercer
When does frost risk typically end in Mercer?
The last hard freeze (28°F) in Mercer typically lands around May 9, 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 30.
When is the first frost in Mercer?
The first hard freeze (28°F) in Mercer typically arrives around Oct 4, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 20, so the watching starts about Sep 4 — about 148 days after the spring freeze cleared.
How long is the growing season in Mercer?
Measured between 28°F hard freezes, Mercer sees about 148 frost-free days — roughly May 9 through Oct 4, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 30 to Sep 20, about 113 days.
Is the soil safe to grow vegetables in Mercer?
The federal record around Mercer shows 100 documented sites, mostly Underground Storage Tanks entries (77), the nearest Brownfields record about 0.4 miles 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 gardeners stretch the season in Mercer?
With about 148 frost-free days between hard freezes, Mercer rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 176 to 204 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 9 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Mercer's scale — its 4a band and its 148-day season. Your yard writes its own version of Mercer'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 Mercer’s own scale
6 of the readings below were taken at Mercer's own scale — its own ~148-day season between 28°F freezes, the 2,849 acres it covers and 100 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Mercer's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Mercer's own 28°F hard-freeze dates, about May 9 and Oct 4 and the ~148-day span between themNOAA 1991–2020 Climate Normals
- 100 documented contamination sites on the federal record near Mercer, the closest Brownfields record about 0.4 miles out from the town centreFederal environmental registers
- Mercer's boundary and the 2,849 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~148-day seasonGrowable Ground crop-matching engine
- The ecoregion at Mercer's own centroid, the Northern Lakes and ForestsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Mercer's 2,849 acres read through its county's SSURGO summaryfrom Iron County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Iron 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 Iron County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Mercer's 2,849 acreswhy one lot differs from the next →
- Which side of Mercer you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,849 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.4 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 Mercer-wide figureread your own land →