Can I Grow Sweet Autumn Clematis in Wisconsin?

Sweet Autumn Clematis in Wisconsin — the short answer

Wisconsin is not one climate

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 sweet autumn clematis (USDA PHZM 2023):

Zone Comparison

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 Sweet Autumn Clematis in Wisconsin

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 sweet autumn clematis survives winter in part of Wisconsin, not across all of it. Whether the season is long enough — and warm enough — is a different question.

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

Sweet Autumn Clematis likes near-neutral soil (pH 5.5-7.5). 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, a raised bed lifts the roots above wet ground, or work in compost. pH range, preferred pH and drainage need: We haven't confirmed this against a published source yet.

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 Sweet Autumn Clematis in Wisconsin

Zone compatibility tells you about winter cold survival — but Wisconsin growers also need to think about:

What to actually do about these — and the constraints that apply to every Wisconsin grower, not just sweet autumn clematis — is covered on the Wisconsin growing guide.

Where in Wisconsin Sweet Autumn Clematis Is Zone-Hardy

Sweet Autumn Clematis is rated for USDA zones 5–9. 36 of Wisconsin’s 72 counties fall inside that band. The coldest that does is Ashland County at zone 5a. 36 counties sit below the plant’s zone 5 floor, where an unprotected plant is relying on snow cover and a mild year. Where you are in Wisconsin decides this one.

Across those 72 counties Wisconsin’s winter-low ladder runs from zone 4a in Bayfield County to zone 6a in Racine County — 2 USDA zones of spread, which is 20°F between the two counties’ average coldest night of the year. That is why a statewide hardiness answer is where you start and not where you finish.

The planting window moves with it. Florence County holds its last hard freeze (28°F) until about May 16, while Milwaukee County is clear by Apr 5 — 41 days apart. Set sweet autumn clematis out on your county’s date, not the state’s.

County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F killing freeze — earlier than the folk 32°F "last frost". Sweet Autumn Clematis’s zone 5–9 band: Rated hardy to zone 5a by NC State Extension Gardener Plant Toolbox, checked Oct 2026. Ceiling: not verified.. A parcel report resolves your address’s own zone and frost dates rather than its county’s.

Pollinator + Wildlife Value

Sweet Autumn Clematis draws honeybees and native bees (moderate value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, sweet autumn clematis 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. Pollinator value: We haven't confirmed this against a published source yet.

Wisconsin Cooperative Extension

For Wisconsin-specific cultivar recommendations, planting calendars, and pest pressure for sweet autumn clematis, 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 Sweet Autumn Clematis native to Wisconsin?

No — the USDA PLANTS Database lists Sweet Autumn Clematis as introduced rather than native in the Lower 48, so it is not part of Wisconsin's native flora. It grows here as a garden plant; pairing it with a few Wisconsin natives keeps local pollinators fed too.

Looking for plants that belong here? The Wisconsin growing guide lists plants that USDA PLANTS records growing in Wisconsin and that Kew and NatureServe Explorer both list in its native range, leaving out any that NatureServe flags as exotic there or that our audit holds.

State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.

Common Questions About Growing Sweet Autumn Clematis in Wisconsin