Growing Sweet Potatoes in a Northern Garden | The Old Farmer's Almanac

Growing Sweet Potatoes

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Robin Sweetser
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One vegetable that I love but had never grown before this year is the sweet potato. Sweet potatoes are tropical vegetables, so usually grown in southern states.

My mother-in-law was a transplanted southern belle who longed to grow the foods she grew up with in the Deep South here in frigid New Hampshire. Sorry to say but she did not have any luck with lima beans, peanuts, okra, or sweet potatoes. A few years ago the University of New Hampshire experimented with growing sweet potatoes with great success so I knew it could be done here in the frozen north and this year I gave it a try.

What is a Sweet Potato?

Sweet potatoes (Ipomoea batatas) are not related to regular white potatoes, belonging instead to the morning glory family—Convolvulaceae.


Their heart-shaped leaves are a reminder of that relationship. They are not a tuber but a fleshy root native to Central and South America. Depending on the variety they can have dry or moist flesh in colors ranging from white to yellow, orange, red, and even purple!

The Difference Between Sweet Potatoes and Yams

Just don’t call ‘em yams! True yams are from a different plant family—Dioscorea. They are huge tubers with rough scaly skin, grown mostly in West Africa and tropical Asia where they can get the 8 to 10 month growing season they need to mature. Yams can grow to be 3 to 4 feet long and weigh up to 80 pounds!

Growing Sweet Potatoes

This spring I bought an organically grown sweet potato at the grocery store and planted it in a shallow pot to sprout. I snapped off the sprouts after they had developed some leaves and potted them up in small pots until it was warm enough to plant them outside.

Unfortunately, by the time the weather was settled and warm enough for the sweet potatoes, our garden beds were full so I resorted to growing them in some large grow bags. The vines grew great all summer long and when frost threatened I dug them out of the bags.


Each plant yielded 2 to 6 potatoes of varying sizes.


The ones in the smallest container grew all curly so I guess they needed more room to spread. Next year I will save them some garden space and try again but in open ground this time.

Curing Sweet Potatoes

The most difficult part of the experiment was the curing process. After harvest, they need to be kept at 85 degrees and 85% humidity for 5 to 10 days to convert the starches into sugar, giving them their sweet flavor. Not easy to do in NH in October.

I faithfully ran them out to the greenhouse on sunny days and brought them in at night. I hope it worked because I am planning on having sweet potatoes for Thanksgiving.

If you want to try growing them, slips can be ordered from seed companies or you can start your own by rooting in soil as I did or by rooting in water. Just suspend a sweet potato halfway in a glass of water about 6-8 weeks before your last frost date. Toothpicks come in handy for this, just poke in 3 or 4 to hold the potato halfway out of the water. Snap off the slips and plant them outside once the soil has warmed to 60 degrees.

About The Author

Robin Sweetser

Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. Read More from Robin Sweetser

2023 Gardening Club