Root Vegetable

When to Plant Sweet Potatoes in Wisconsin

Not related to regular potatoes at all. Sweet potatoes need heat and a long growing season but reward with incredible harvests.

The Short Answer

In Wisconsin, soil conditions are an important factor for sweet potatoes. Rich agricultural soils in southern half. Sandy soils in central plain. Heavy clay in some lake regions. Generally fertile.

Wisconsin Frost Dates

Your planting dates depend on which part of Wisconsin you're in. Here are the frost date ranges by region:

Region Zones Last Frost (Spring) First Frost (Fall)
Northern Wisconsin 3b, 4a May 15 - Jun 1 Sep 10 - Sep 25
Central Wisconsin 4a, 4b May 5 - May 20 Sep 20 - Oct 5
Southern Wisconsin 4b, 5a, 5b Apr 25 - May 10 Oct 1 - Oct 15

Sweet Potatoes Planting Schedule for Wisconsin

Northern Wisconsin (Zones 3b, 4a)

Average last frost: May 15 - Jun 1 · Average first frost: Sep 10 - Sep 25

Start Seeds Indoors
8 wks before frost
Transplant Outside
3 wks after frost

Central Wisconsin (Zones 4a, 4b)

Average last frost: May 5 - May 20 · Average first frost: Sep 20 - Oct 5

Start Seeds Indoors
8 wks before frost
Transplant Outside
3 wks after frost

Southern Wisconsin (Zones 4b, 5a, 5b)

Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15

Start Seeds Indoors
8 wks before frost
Transplant Outside
3 wks after frost

Growing Sweet Potatoes in Wisconsin

Sweet Potatoes in Wisconsin's Climate

Sweet potatoes are a stretch in cold climates — the crop needs 90+ days of warm soil and air. Southern zones 5b-5a gardeners can succeed with Beauregard (90 days), black plastic mulch, and raised beds. Northern zone 3-4 gardeners should skip sweet potatoes — the season simply isn't long enough. Container growing on a sun-baked patio sometimes works where in-ground doesn't.

Soil Considerations for Wisconsin

Rich agricultural soils in southern half. Sandy soils in central plain. Heavy clay in some lake regions. Generally fertile. Loose, well-drained soil is especially important for sweet potatoes since the edible portion grows underground. If your soil is heavy clay, consider raised beds.

Wisconsin Climate & Growing Season

Cold winters. Warm summers. Lake Michigan moderates eastern climate. Good growing season in south. Short season in north. Sweet Potatoes cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.

Growing season length varies across Wisconsin: Northern Wisconsin (3b, 4a) has a last frost around May 15 - Jun 1, while Southern Wisconsin (4b, 5a, 5b) sees frost end around Apr 25 - May 10. This difference matters for sweet potatoes — transplant timing shifts by several weeks across the state.

Growing Tips

Grow from slips, not seeds. Start slips from a sweet potato in water 8 weeks before transplanting. Cure harvested tubers in warmth for 10 days.

Companion Planting

Plant sweet potatoes alongside these companions for better growth:

Beans Corn

Keep sweet potatoes away from:

Squash

The Bottom Line

Sweet Potatoes can be grown successfully across Wisconsin, but your exact planting dates depend on which region you're in. Northern Wisconsin gardeners should plan around a May 15 - Jun 1 last frost, while those in Southern Wisconsin can typically plant earlier. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Sweet Potatoes Growing Guide National planting guide with all states Wisconsin Planting Calendar All plants for Wisconsin Sweet Potatoes in Alabama Alabama planting dates Sweet Potatoes in Alaska Alaska planting dates Sweet Potatoes in Arizona Arizona planting dates Sweet Potatoes in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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