Generally — Most Areas
black walnut (zones 4-9) suits most of Wisconsin (3b-6a) — zones 4-6 are in range, and the rest of the state is the exception.
Black Walnut in Wisconsin — the short answer
Black Walnut in Wisconsin: hardy in zones 4–9, full sun, against a state median of ~173 frost-free days.
- Plant zones
- 4-9
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Wisconsin zones
- 3b-6a
- USDA PHZM 2023
- Frost window
- Apr 17 - May 2 – Oct 9 - Oct 21
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 140 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 3650 days
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Wisconsin spans zones 3b-6a, but your yard sits in exactly one — and slope, tree cover, and cold-air pockets nudge it further. Enter your address and we'll score black walnut against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Wisconsin is not one climate
Wisconsin’s winter-low ladder runs across 72 counties, from zone 4 in Bayfield County to zone 6 in Racine County. That is 20°F between the two counties’ average coldest night — the difference between black walnut overwintering in the ground and coming under cover.
The middle half of 72 counties runs 4.5–5 zones, with a median of 4.5 zones — a 2-zone span end to end.
Measured across 72 Wisconsin counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where in Wisconsin Fits Best
Even within Wisconsin's zones 3b-6a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for black walnut (USDA PHZM 2023):
Zone Comparison
Black Walnut Needs
- USDA Zones: 4-9
- Frost-Free Days: 150+
- Sun: Full Sun
- Mature size: 75 ft tall
- Drought tolerance: Low
Wisconsin Has
- USDA Zones: 3b-6a
- Last Hard Freeze (28°F): Apr 17 - May 2
- First Hard Freeze (28°F): Oct 9 - Oct 21
- Annual Rainfall: 28-34 inches
- Common Soils: Silt loam, Clay loam, Sandy outwash
Plant Zone Range (zones 4-9)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Black Walnut in Wisconsin
The frost window
Across Wisconsin, the last spring hard freeze (28°F) clears between Apr 17 and May 2, and the first fall hard freeze lands between Oct 9 and Oct 21 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 160-day window you can count on — up to 187 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Winter standing
Wisconsin runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for black walnut, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether black walnut is a permanent planting or a replant-every-spring crop for you turns on your own zone within Wisconsin; check its hardiness range against that before treating it as long-lived ground.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says black walnut survives winter in part of Wisconsin, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Black Walnut wants 150+ frost-free days; a typical Wisconsin site sees ~173 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
Growing degree days
Black Walnut needs ~2500 GDD (base 50°F) to ripen. The state median runs ~2102 GDD (from PRISM 1991-2020 climate normals), so Wisconsin's typical season runs short on heat — pick a south-facing site and consider season extension.
Chill hours
Black Walnut requires ~1000 chill hours (32-45°F dormancy window). Wisconsin typically banks ~2500 chill hours per winter (from PRISM 1991-2020 climate normals), which keeps this plant on track.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Black Walnut likes near-neutral soil (pH 5.8-8.3). That's the common-ground band across Wisconsin's silt loam and clay loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6.5 and 7.5 — worth knowing before you decide whether a Wisconsin soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Wisconsin site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Wisconsin soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant black walnut for food
Anything you grow to eat takes up what is in the ground it grows in, so what is on record near you is worth knowing before black walnut goes in. What follows is Wisconsin’s documented federal record at state scale — a screening signal, not a soil test, and not a statement about any one lot.
Safe to Grow Here?
What the federal record shows across Wisconsin — and how to grow with it.
We checked the federal record across Wisconsin — 57,912 documented sites across 8 of the 9 source types we track.
The most significant on record: 314 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Wisconsin carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources Checked
across Wisconsin
Severity Distribution
across Wisconsin
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What Else to Consider for Black Walnut in Wisconsin
Zone compatibility tells you about winter cold survival — but Wisconsin growers also need to think about:
Cold winters (-30F in northern WI)
Short growing season (110-140 frost-free days)
Sandy central soils drain too quickly
What to actually do about these — and the constraints that apply to every Wisconsin grower, not just black walnut — is covered on the Wisconsin growing guide.
Timing shifts within Wisconsin
Black Walnut needs about 150 days of frost-free season to complete its cycle. 67 of Wisconsin’s 72 counties give it that outright. The tightest that does is Iron County at 150 frost-free days — 0 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Wisconsin’s 72 counties the frost-free season runs from 140 days in Florence County to 217 days in Milwaukee County — a spread of 77 days, which is why a single statewide planting date misleads. The median Wisconsin county sees 173 frost-free days, leaving black walnut about 23 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Black Walnut's 150-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Wisconsin Cooperative Extension
For Wisconsin-specific cultivar recommendations, planting calendars, and pest pressure for black walnut, the canonical source is UW–Madison Division of Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Black Walnut native to Wisconsin?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Black Walnut as native to Wisconsin. Planting it supports the pollinators and wildlife that evolved alongside it.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
What pests threaten black walnut in Wisconsin?
Japanese beetle is documented in Wisconsin and will find black walnut, but it is manageable here. What an experienced grower watches for, and does:
Japanese beetle
Worth watchingThe University of Kentucky lists this among the landscape plants Japanese beetles are most likely to attack, and the skeletonized, lace-like leaves can look alarming. But the honest calibration is the University of Minnesota's: a healthy, established tree, shrub or vine tolerates a lot of this feeding without significant, long-term injury — in most cases the damage is cosmetic and will not kill the plant.
What to do: For an established planting the move is to leave it be and keep it watered through the four-to-six-week flight — a vigorous plant outgrows feeding that looks worse than it is. Young or already-stressed plants are the exception and worth hand-protecting: knock beetles into soapy water in the cool of morning, when they are slow. The one thing not to hang is a Japanese beetle trap — University of Kentucky research found the lures pull in far more beetles than they catch.
Documented range: states listed as Japanese-beetle infested · University of Kentucky Entomology, University of Minnesota Extension, National Plant Board
Only pests whose documented range and host relationship both trace to a primary source appear here — so a quiet section means we have nothing sourced to tell you, not that your garden is pest-free.
Common Questions About Growing Black Walnut in Wisconsin
When can I plant Black Walnut in Wisconsin?
Wisconsin's last spring hard freeze (28°F) clears between Apr 17 and May 2, and the first fall hard freeze lands between Oct 9 and Oct 21 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Black Walnut, so this page does not state whether it overwinters in Wisconsin and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Black Walnut grown in across Wisconsin?
Wisconsin spans USDA hardiness zones 3b-6a (USDA ARS PHZM 2023). Black Walnut carries a range of zones 4-9, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Wisconsin site have?
A typical Wisconsin site sees ~173 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Black Walnut needs 150+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Black Walnut native to Wisconsin?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Black Walnut as native to Wisconsin. Planting it supports the pollinators and wildlife that evolved alongside it.
How should I amend the soil for Black Walnut in Wisconsin?
Black Walnut prefers pH 5.8-8.3 and well (dry spells) drainage (FAO ECOCROP). That sits in the common-ground band across Wisconsin soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Black Walnut actually grow on my specific land in Wisconsin?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores black walnut against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Wisconsin
State-level data is a sketch. Your Growable Ground report scores black walnut against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Wisconsin black walnut averages can't show:
We read public map data around Wisconsin — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Wisconsin black walnut average
Explore More
Growing guides for black walnut
Explore Wisconsin county by county
Wisconsin carries 72 counties with their own USDA zone — a sample of the growing pages for black walnut there:
Where else black walnut grows
Black Walnut's zone band crosses state lines — these are the states closest to Wisconsin in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Wisconsin
Wisconsin has a growing page for 806 plants — a rotating sample of the rest of the shelf.
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