Wisconsin potato planting happens after the soil thaws and dries enough to work, and knowing exactly When To Plant Potatoes In Wisconsin can make the difference between a bumper crop and a disappointing harvest. The timing depends on your specific region, soil temperature, and the variety you choose. This guide walks you through everything you need to know to get your spuds in the ground at the perfect moment.
Potatoes are a cool-season crop that thrive in Wisconsin’s spring weather. They can handle light frosts, but the soil must be workable—not frozen or waterlogged. Aim for soil temperatures around 45°F to 50°F at a depth of 4 inches.
When To Plant Potatoes In Wisconsin
The general rule is to plant potatoes 2 to 4 weeks before your last expected spring frost. In most of Wisconsin, that means planting between mid-April and early May. Southern parts can start earlier, while northern areas wait until late April or early May.
Check your local frost dates. For example, Madison’s last frost is around May 5, so planting in mid-April works. In Superior, the last frost is later, around May 15, so you’d plant in late April.
Soil Temperature Is Critical
Potatoes won’t grow well in cold, wet soil. They can rot if planted too early. Use a soil thermometer to check the temperature at 4 inches deep. If it’s below 45°F, wait a few days.
If you don’t have a thermometer, watch for signs like soil that crumbles easily when squeezed. If it forms a muddy ball, it’s too wet.
Regional Planting Windows
Wisconsin has three main growing zones: southern, central, and northern. Here’s a breakdown:
- Southern Wisconsin (Zones 5a-5b): Plant from April 10 to April 25. Examples: Milwaukee, Madison, Kenosha.
- Central Wisconsin (Zones 4b-5a): Plant from April 20 to May 5. Examples: Wausau, Stevens Point, Wisconsin Rapids.
- Northern Wisconsin (Zones 3b-4a): Plant from April 25 to May 15. Examples: Rhinelander, Hayward, Superior.
These are guidelines. Always adjust based on your microclimate and current weather.
Choosing The Right Potato Varieties
Not all potatoes are created equal for Wisconsin’s climate. Some mature faster, which helps avoid late blight or early frosts in fall.
Early Season Varieties
These mature in 70 to 90 days. Plant them first for a summer harvest.
- Red Norland
- Yukon Gold
- Dark Red Norland
- Caribe
Mid Season Varieties
These take 90 to 110 days. They’re great for storage and general use.
- Kennebec
- Russet Burbank
- French Fingerling
- All Blue
Late Season Varieties
These need 110 to 135 days. Only plant them if you have a long, mild fall.
- German Butterball
- Purple Viking
- Russet Norkotah
For most Wisconsin gardeners, a mix of early and mid-season varieties works best. You get new potatoes in July and storage spuds by September.
Preparing Your Seed Potatoes
Seed potatoes are small tubers or pieces of larger ones. Buy certified disease-free seed potatoes from a garden center or online. Don’t use grocery store potatoes—they may carry diseases.
Cutting And Curing
If your seed potatoes are larger than a chicken egg, cut them into pieces. Each piece should have at least 2 “eyes” (sprouting points). Cut them a day or two before planting to let the cut surfaces heal. This prevents rot.
- Cut the potatoes into 1.5 to 2 inch chunks.
- Place them in a cool, dark place (60°F to 70°F) for 24 to 48 hours.
- Check for a dry, calloused surface before planting.
Small seed potatoes can be planted whole. That’s easier and reduces disease risk.
Planting Step By Step
Once your soil is ready and your seed pieces are cured, follow these steps:
- Dig trenches: Make trenches 4 to 6 inches deep, spaced 2 to 3 feet apart.
- Add compost: Mix in a handful of compost or aged manure per foot of trench.
- Place seed pieces: Set them 12 to 15 inches apart, eyes facing up.
- Cover with soil: Fill the trench with 3 to 4 inches of soil. Don’t mound it yet.
- Water lightly: If the soil is dry, give them a gentle watering.
Don’t plant too deep. Potatoes need sunlight to grow stems, but the tubers form in the dark soil. Shallow planting helps them warm up faster.
Aftercare And Hilling
As the plants grow, you’ll need to “hill” them. This means pulling soil up around the stems to cover developing tubers. If tubers are exposed to sunlight, they turn green and become toxic.
When To Hill
Hill the plants when they are about 6 to 8 inches tall. Repeat every 2 to 3 weeks until the plants flower or the vines die back.
- First hilling: Cover stems up to 4 inches.
- Second hilling: Add another 3 to 4 inches.
- Final hilling: Mound soil 6 to 8 inches high.
Use loose soil or straw for hilling. Avoid compacting the soil, which can hinder tuber growth.
Watering And Fertilizing
Potatoes need consistent moisture, especially during tuber formation. That’s usually 4 to 6 weeks after planting.
Watering Tips
- Give them 1 to 2 inches of water per week.
- Water deeply once or twice a week, not shallowly every day.
- Stop watering 2 to 3 weeks before harvest to let skins harden.
Fertilizing
Potatoes are heavy feeders. Apply a balanced fertilizer (like 10-10-10) at planting time. Side-dress with a low-nitrogen fertilizer (like 5-10-10) when plants are 6 inches tall. Too much nitrogen makes big vines but small tubers.
You can also use compost tea or fish emulsion for a gentle boost.
Common Pests And Diseases
Wisconsin potatoes face a few common issues. Here’s how to handle them.
Colorado Potato Beetle
These yellow-and-black striped beetles eat leaves. Handpick them or use neem oil. Rotate crops yearly to reduce infestations.
Late Blight
This fungal disease causes dark spots on leaves and tubers. It thrives in cool, wet weather. Plant resistant varieties and avoid overhead watering.
Scab
Scab causes rough, corky patches on tubers. It’s worse in alkaline soil. Keep soil pH below 6.0 and use resistant varieties like Russet Burbank.
Wireworms
These thin, brown larvae tunnel into tubers. Rotate crops and avoid planting after sod or grass.
Harvesting Your Potatoes
You can harvest new potatoes (small, thin-skinned) about 2 to 3 weeks after the plants flower. For full-sized storage potatoes, wait until the vines die back completely.
How To Harvest
- Use a garden fork to gently lift the soil around the plants.
- Pull up the entire plant and collect the tubers.
- Brush off excess soil, but don’t wash them until you’re ready to eat.
- Cure storage potatoes in a dark, humid place at 50°F to 60°F for 10 to 14 days.
Curing helps the skins thicken, which improves storage life. After curing, store them in a cool, dark place (40°F to 45°F) with good air circulation.
Extending The Season
If you want a longer harvest, try a second planting in late June or early July. This works for early-maturing varieties. You’ll get fall potatoes before the first hard frost.
In southern Wisconsin, you can plant a second crop by July 1. In northern areas, aim for June 15. Use varieties that mature in 70 to 80 days.
Another trick is to use row covers or plastic mulch to warm the soil in spring. This lets you plant a week or two earlier.
Frequently Asked Questions
What Is The Best Month To Plant Potatoes In Wisconsin?
Mid-April to early May is best for most of Wisconsin. Southern areas can start in mid-April, while northern areas wait until late April or early May.
Can I Plant Potatoes In June In Wisconsin?
Yes, but only for early-maturing varieties. Plant by June 15 in northern areas and July 1 in southern areas. You’ll harvest before the first fall frost.
How Deep Should I Plant Potato Seeds?
Plant seed pieces 3 to 4 inches deep. Cover them with soil, then hill them as they grow. This prevents greening and boosts yield.
Do Potatoes Need Full Sun In Wisconsin?
Yes, they need at least 6 to 8 hours of direct sunlight daily. More sun means bigger tubers. Shade reduces yield and increases disease risk.
What Happens If I Plant Potatoes Too Early In Wisconsin?
Cold, wet soil can cause seed pieces to rot. They may also sprout slowly and produce weak plants. Wait until soil temperature reaches 45°F.
Final Tips For Success
Potatoes are forgiving, but a little planning goes a long way. Here are some last pointers:
- Rotate your potato patch every year to avoid soil-borne diseases.
- Use raised beds if your soil is heavy clay. They drain better and warm up faster.
- Mulch with straw to keep soil cool and moist, and to prevent weeds.
- Harvest on a dry day to reduce rot during storage.
- Save a few small tubers for next year’s seed, but only if they’re disease-free.
Growing potatoes in Wisconsin is rewarding. With the right timing and care, you’ll have a steady supply from summer through winter. Start prepping your soil now, and you’ll be enjoying homegrown spuds before you know it.
Remember, the key is patience. Let the soil warm up naturally, and don’t rush the planting. Your potatoes will thank you with a bountiful harvest.
Happy gardening, and enjoy your Wisconsin-grown potatoes!