Generally — Most Areas
sweetspire (zones 5-11) suits most of Wisconsin (3b-6a) — zones 5-6 are in range, and the rest of the state is the exception.
Sweetspire in Wisconsin — the short answer
Sweetspire in Wisconsin: hardy in zones 5–11, shade, against a state median of ~173 frost-free days.
- Plant zones
- 5-11
- 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
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 sweetspire against your parcel's actual hardiness, soil, and sun.
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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 sweetspire 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
Sweetspire is rated for zones 5–11 — a cold floor USDA puts at -20 to -10°F. Against Wisconsin’s 72 counties that band holds in 36 of them, and the line runs at Ashland County (zone 5a), the coldest county still inside it.
Inside zones 5–11
36 counties
- Columbia County · zone 5a
- Crawford County · zone 5a
- Dodge County · zone 5a
3 of 36 shown
Below the zone 5 floor
36 counties
- Bayfield County · zone 4a
- Burnett County · zone 4a
- Douglas County · zone 4a
3 of 36 shown
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Even within Wisconsin's zones 3b-6a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for sweetspire (USDA PHZM 2023):
Zone Comparison
Sweetspire Needs
- USDA Zones: 5-11
- Frost-Free Days: 180+
- Sun: Shade
- Mature size: 6 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 5-11)
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 Sweetspire 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 sweetspire, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether sweetspire 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 sweetspire 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
Sweetspire wants 180+ frost-free days; a typical Wisconsin site sees ~173 (NOAA Regional Climate Centers ACIS, 1991-2020) — 7 days short of what it needs. A typical Wisconsin season does not carry this crop to harvest outdoors, and a gap that size is not one an earlier sowing date or a faster cultivar closes; growing it here means growing it under cover.
Chill hours
Sweetspire requires ~400 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
Sweetspire tolerates a wide pH range (pH 4-7.5) — 3.5 units, acid ground through alkaline — so soil acidity is rarely what limits it in Wisconsin. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant.
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.
What Else to Consider for Sweetspire 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 sweetspire — is covered on the Wisconsin growing guide.
Timing shifts within Wisconsin
Sweetspire needs about 180 days of frost-free season to complete its cycle. 28 of Wisconsin’s 72 counties give it that outright. The tightest that does is Green Lake County at 180 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, which is 7 days short of what sweetspire needs — so on a typical Wisconsin parcel this is a transplant-or-protect crop, not a direct-sow one.
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"). Sweetspire's 180-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Sweetspire draws honeybees, native bees, and butterflies (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, sweetspire can only work that bloom inside Wisconsin's frost window — roughly 173 days, opening after the last 28°F freeze (Apr 17 - May 2) and closing at the first (Oct 9 - Oct 21), per NOAA Regional Climate Centers ACIS, 1991-2020.
Wisconsin Cooperative Extension
For Wisconsin-specific cultivar recommendations, planting calendars, and pest pressure for sweetspire, 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 Sweetspire native to Wisconsin?
Sweetspire is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Wisconsin. It can still earn a place in a Wisconsin garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The Wisconsin growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Sweetspire in Wisconsin
When can I plant Sweetspire 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 Sweetspire, 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 Sweetspire grown in across Wisconsin?
Wisconsin spans USDA hardiness zones 3b-6a (USDA ARS PHZM 2023). Sweetspire carries a range of zones 5-11, 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). Sweetspire needs 180+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Sweetspire native to Wisconsin?
Sweetspire is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Wisconsin. It can still earn a place in a Wisconsin garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Sweetspire in Wisconsin?
Sweetspire tolerates pH 4-7.5 (USDA PLANTS). That is a 3.5-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Wisconsin site — amend for drainage and organic matter first.
Will Sweetspire actually grow on my specific land in Wisconsin?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sweetspire 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 sweetspire against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Wisconsin sweetspire 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 sweetspire average
Explore More
Growing guides for sweetspire
Explore Wisconsin county by county
Wisconsin carries 72 counties with their own USDA zone — a sample of the growing pages for sweetspire there:
Where else sweetspire grows
Sweetspire'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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