Ask a Master Gardener: Growing sweet potatoes is a challenge for northern gardeners
Give some thought to planning if you're going to give it a try next season.
Q: Since I can’t have a big Thanksgiving gathering this year, I’m already thinking about next year, and I’m thinking it would be fun to try to grow more of the vegetables for the meal in my garden. Can you grow sweet potatoes or yams in northern Minnesota? Any tips?
A: Sweet potatoes are certainly worth a try, but keep these things in mind: They will take up a lot of room in the garden; and they would really rather grow somewhere warmer than northern Minnesota, with a longer growing season, so you’ll need to coddle them. If you live close to Lake Superior, where frosts tend to come later in fall than they do farther inland, you may have better luck.
Sweet potatoes are normally planted as “slips,” not seeds. These are cuttings from a sprouting sweet potato. You can sprout your own, but lots of seed companies sell them ready to go. Look for varieties that have the shortest period to maturity you can find — 100 days or less.
Sweet potatoes should be grown in full sun. Raised beds are a good idea, for warmth and drainage. The soil should contain organic matter such as compost. Cover the soil with black plastic mulch to help keep the plants warm, punching holes every 12 to 18 inches to plant your slips in. Rows should be 3 to 4 feet apart to give the vines room to grow. Plant the slips after the danger of frost has passed and the soil has warmed up.
The plastic mulch makes for less weeding, but it makes watering a bit more of a challenge. You can run a drip tape under the plastic, or just carefully water the holes in the plastic that the plants are growing out of.
Let the plants grow for as long as possible, until frost returns, and then gently dig out your sweet potatoes. Be careful not to bruise them. If you want to store them until Thanksgiving, they will need to be cured in a warm, humid location (ideally 80 to 85 degrees) for a week, and then stored in a cool location (55 degrees).
If you’re up for all that, sweet potatoes are worth a shot in the garden. True yams are not. Yams only grow in the tropics.
Written by U of M Extension Master Gardeners in St. Louis County. Send questions to email@example.com.