Merrimac, Wisconsin, sits in USDA hardiness zone 5a — a zone band wide enough that plant choice, not possibility, is the interesting question.
A short list that earns its place here — cabbage, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Merrimac, 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 Merrimac 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 Merrimac — soil, climate, flood, and parcel records. How we handle your address.
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Merrimac — the short answer
Merrimac, Wisconsin: USDA zone 5a, about 180 days between hard freezes, across 527 acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 16
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~180
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 527 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 Merrimac's average, not your lot's — a low corner or a tree line moves it. Against Merrimac's 180-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Merrimac
Each reading below is measured for Merrimac itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredMerrimac runs about 180 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
MeasuredMerrimac 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 Merrimac is in
Merrimac sits in the Southeastern Wisconsin Till Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Merrimac's own centroid, and it is not what its county reads: Sauk County is mostly Driftless Area. The wider page above you is answering a different question about different ground.
What Grows in Merrimac
Every plant below cleared Merrimac's own zone 5a and its 180-day season. Each card opens that plant's Wisconsin profile. How we score.
Is it too late to plant in Merrimac?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 22; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 19 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 16 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Merrimac
Closest first, within ~10 miles of Merrimac. Listing isn't leaking, and distance isn't exposure.
- FERRY CROSSING BAR & GRILLUnderground Storage Tanks · 950 ft
- KEEVILSUnderground Storage Tanks · 1000 ft
- SK-10/07E/02-0050Nitrate · 1200 ft
- MERRIMAC FIRE DEPTUnderground Storage Tanks · 1200 ft
- MERRIMAC MOBILUnderground Storage Tanks · 1200 ft
- M & I BANKUnderground Storage Tanks · 1300 ft
- Village Of Merrimac - Cook StreetUnderground Storage Tanks · 1300 ft
- Ferry Landing Resort & MarinaUnderground Storage Tanks · 1600 ft
- W C NADOLNYUnderground Storage Tanks · 1700 ft
- VILLAGE OF MERRIMACUnderground Storage Tanks · 2000 ft
- CO-10/07E/11-0215Nitrate · 1.4 mi
- Sunset Harbor MarinaUnderground Storage Tanks · 1.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Merrimac'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 Merrimac.
Total Sites
401
within ~10 miles of Merrimac
Risk Level
Elevated
Highest-severity
4 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Merrimac
Severity Distribution
within ~10 miles of Merrimac
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Merrimac, Underground Storage Tanks runs higher than the national average — 252 sites within ~10 miles of Merrimac. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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 Merrimac
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 Merrimac average
Your land is one point inside Merrimac
Everything above resolves to Merrimac as a whole — one PHZM band and one 28°F frost record, read across 527 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 Merrimac Average
Merrimac Average
- ●USDA Zones 5a, averaged across Merrimac
- ●One soil character for all of Merrimac
- ●Frost dates read at Merrimac's scale: Apr 19 to Oct 16
YOUR Parcel
- ✓Your exact zone, not Merrimac's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Merrimac
Pull a site-specific report for your exact address in Merrimac, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Merrimac averages can't show:
We read public map data around Merrimac — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Merrimac average
How we know this about Merrimac
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 Merrimac’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 Merrimac
When does frost risk typically end in Merrimac?
The last hard freeze (28°F) in Merrimac typically lands around Apr 19, 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 10.
When is the first frost in Merrimac?
The first hard freeze (28°F) in Merrimac typically arrives around Oct 16, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 2, so the watching starts about Sep 16 — about 180 days after the spring freeze cleared.
How long is the growing season in Merrimac?
Measured between 28°F hard freezes, Merrimac sees about 180 frost-free days — roughly Apr 19 through Oct 16, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 10 to Oct 2, about 145 days.
Is the soil safe to grow vegetables in Merrimac?
The federal record around Merrimac is a meaningful one — 401 documented sites, mostly Underground Storage Tanks entries (252), the nearest Underground Storage Tanks record about 0.2 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Merrimac?
From about Sep 16 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 16 (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 16. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Merrimac's scale — its 5a band and its 180-day season. Your yard writes its own version of Merrimac'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 Merrimac’s own scale
6 of the readings below were taken at Merrimac's own scale — its own ~180-day season between 28°F freezes, the 527 acres it covers and 401 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Merrimac's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Merrimac's own 28°F hard-freeze dates, about Apr 19 and Oct 16 and the ~180-day span between themNOAA 1991–2020 Climate Normals
- 401 documented contamination sites on the federal record near Merrimac, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Merrimac's boundary and the 527 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~180-day seasonGrowable Ground crop-matching engine
- Merrimac sits in the Southeastern Wisconsin Till Plains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Merrimac's 527 acres read through its county's SSURGO summaryfrom Sauk County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Sauk 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 Sauk County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Merrimac's 527 acreswhy one lot differs from the next →
- Which side of Merrimac you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 527 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Merrimac-wide figureread your own land →
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