Minnesota’s extreme winters push sweet potato planting to late May or early June for best results. Knowing the best time to plant sweet potato in Minnesota is the single most important step for a successful harvest in this challenging climate. Get the timing wrong, and your crop may fail before it even starts.
Sweet potatoes need warmth. They are not like regular potatoes. They come from tropical regions. So, Minnesota’s short, cool spring can be a problem. But with the right plan, you can grow a great crop.
Understanding Minnesota’s Growing Season
Minnesota has a short growing season. The last frost usually happens in mid-May. But the soil stays cold for a while after that. Sweet potatoes need warm soil to grow.
You cannot rush them. Planting too early in cold soil will rot the slips. You need to wait for consistent warmth. That is why late May or early June is the sweet spot.
Frost Dates And Soil Temperature
Check your local frost dates. The average last frost date in southern Minnesota is around May 15. In northern areas, it can be late May or early June. But frost is not the only thing to watch.
Soil temperature is more important. Sweet potatoes need soil at least 60°F (15°C) to start. They grow best when soil is 70°F to 80°F (21°C to 27°C). Use a soil thermometer to check. Do not guess.
- Wait until soil is consistently above 60°F.
- Check the 10-day forecast before planting.
- Cold, wet soil will kill slips quickly.
Best Time To Plant Sweet Potato In Minnesota
The ideal window is from late May to early June. This gives the soil time to warm up. It also avoids the risk of a late frost. In southern Minnesota, aim for the last week of May. In northern areas, the first week of June is safer.
If you plant too late, the growing season becomes too short. Sweet potatoes need 90 to 120 days to mature. Minnesota’s first frost usually comes in late September or early October. So you need to get them in the ground by early June at the latest.
How To Prepare For Planting
Preparation starts weeks before planting. You cannot just put slips in the ground. You need to warm the soil and prepare the bed.
- Choose a sunny spot. Sweet potatoes need full sun, at least 6-8 hours a day.
- Loosen the soil to 12 inches deep. They grow best in loose, sandy loam.
- Add compost or aged manure. Do not use too much nitrogen.
- Cover the soil with black plastic a week before planting. This warms it faster.
Black plastic is very helpful in Minnesota. It traps heat and warms the soil by several degrees. It also blocks weeds. You can cut holes in it to plant the slips.
Choosing The Right Varieties
Not all sweet potatoes grow well in Minnesota. You need short-season varieties. Look for ones that mature in 90 to 100 days. Some good choices include:
- Beauregard: A classic orange variety, matures in 90-100 days.
- Georgia Jet: Very early, matures in 90 days. Good for cool soil.
- Centennial: Reliable and productive, matures in 100 days.
- Vardaman: A bush type, good for small spaces, matures in 100 days.
Avoid long-season varieties like Japanese sweet potatoes. They need 120 days or more. They will not mature before frost in Minnesota.
How To Plant Sweet Potato Slips
You will not plant seeds. You plant slips, which are rooted sprouts. You can buy them online or from local garden centers. Do not buy them too early. They need to be planted within a few days of arrival.
If you get them early, store them in a cool, dark place. Keep the roots moist. Plant them as soon as the soil is warm.
Step-By-Step Planting Process
- Wait for a cloudy day or plant in the evening. This reduces transplant shock.
- Dig a hole deep enough to cover the roots. The stem should be buried up to the leaves.
- Space slips 12 to 18 inches apart. Rows should be 3 feet apart.
- Water them well after planting. Keep the soil moist for the first week.
- Cover the plants with row cover if a cold night is forecast.
Water is critical right after planting. But do not overwater. Sweet potatoes do not like soggy soil. Water deeply once a week, more if it is very dry.
Using Raised Beds For Better Warmth
Raised beds are great for sweet potatoes in Minnesota. They warm up faster in spring. They also drain better. If you have heavy clay soil, a raised bed is almost necessary.
Build a bed at least 8 inches high. Fill it with loose, sandy soil. Add plenty of compost. The loose soil lets the roots grow big and straight.
Caring For Sweet Potatoes Through Summer
Once planted, sweet potatoes need regular care. They are not high-maintenance, but they do need attention. Weeds are the biggest problem. They compete for nutrients and water.
Watering And Fertilizing
Water deeply but infrequently. Sweet potatoes are drought-tolerant once established. Too much water can cause the roots to rot. Water only when the top inch of soil is dry.
Fertilize lightly. Use a low-nitrogen fertilizer, like 5-10-10. Too much nitrogen makes big leaves but small roots. Apply fertilizer when you plant, and again after a month.
- Use a balanced fertilizer with low nitrogen.
- Do not over-fertilize. It reduces root size.
- Compost tea is a good option for feeding.
Managing Weeds And Pests
Weeds are a constant battle. Mulch around the plants with straw or black plastic. This keeps weeds down and soil warm. Hand-pull any weeds that appear.
Pests are less common in Minnesota. Deer and rabbits may eat the leaves. Use fencing or repellent. Wireworms can damage roots, but they are rare in well-drained soil.
When To Harvest Sweet Potatoes
Harvest time is just as important as planting time. You need to dig them up before the first hard frost. A light frost may damage the leaves, but the roots can survive. A hard frost will ruin them.
Plan to harvest in late September or early October. The exact date depends on when you planted. Count 90 to 100 days from planting. Check the weather forecast regularly.
Signs That Sweet Potatoes Are Ready
You can start checking around 90 days. The leaves will start to yellow. The vines may die back. Dig up one or two test roots. They should be at least 2 inches in diameter.
Do not wait too long. If the leaves are killed by frost, the roots can still be saved. But they will not grow any bigger. Harvest as soon as possible after a frost warning.
- Use a garden fork to loosen the soil.
- Dig carefully to avoid cutting the roots.
- Brush off excess soil. Do not wash them.
- Cure them before storage.
Curing And Storing Sweet Potatoes
Curing is a critical step. It heals small cuts and makes the roots sweeter. You cannot skip it. Curing takes about 10 days.
Place the roots in a warm, humid place. The ideal temperature is 85°F (29°C) with 85% humidity. A small room with a space heater and a humidifier works. Or use a warm closet with a bowl of water.
After curing, store them in a cool, dry place. The ideal storage temperature is 55°F to 60°F (13°C to 15°C). Do not refrigerate them. They will last for several months.
Common Storage Mistakes
Many people make mistakes with storage. Do not store them in a cold basement. Cold makes them hard and flavorless. Do not store them near apples or onions. They absorb odors.
Check them regularly for soft spots. Remove any bad ones immediately. One rotten sweet potato can spoil the whole batch.
Frequently Asked Questions
Can I plant sweet potatoes in July in Minnesota?
It is not recommended. July is too late. The growing season will be too short. The roots will not have time to mature before frost. Stick to late May or early June.
What is the best soil for sweet potatoes in Minnesota?
Loose, sandy loam is best. Heavy clay soil causes misshapen roots. Add compost and sand to improve drainage. Raised beds are a good solution for clay soil.
How do I know if the soil is warm enough to plant?
Use a soil thermometer. Insert it 4 inches deep. Wait until the temperature is consistently above 60°F. Check in the morning and evening. If it stays warm, you are ready.
Can I grow sweet potatoes in containers in Minnesota?
Yes, you can. Use a large container, at least 15 gallons. Fill it with loose potting soil. Place it in full sun. Water more often because containers dry out fast. Harvest before frost.
Do I need to hill sweet potatoes like regular potatoes?
No, you do not. Sweet potatoes grow underground, not on stolons. Hilling is not necessary. Just keep the soil loose and weed-free. Mulch helps keep the soil warm.
Final Tips For Success
Growing sweet potatoes in Minnesota is possible. It just takes planning. The best time to plant sweet potato in minnesota is your most important decision. Get that right, and the rest is easier.
Start preparing your soil early. Use black plastic to warm it. Choose short-season varieties. Water wisely. Harvest before frost. Cure and store properly. Follow these steps, and you will have a good harvest.
Do not be afraid to experiment. Try different varieties. See what works in your microclimate. Keep notes for next year. Each season teaches you something new.
Sweet potatoes are a rewarding crop. They are nutritious and delicious. With a little effort, you can grow them even in Minnesota’s tough climate. Just remember: warm soil, short season, and careful timing.