Growing Sweet Potatoes

February 12, 2019
Sweet Potato Experiment
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 This Blog

Get inspired by Robin Sweetser’s backyard gardening tips and tricks. Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. She and her partner Tom have a small greenhouse business and also sell plants, cut flowers, and vegetables at their local Farmer’s Market.

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Curing sweet potatoes

Tried my first bigger crop of sweet potatoes, last year, in a 100 gallon grow bag (just 4' in diameter, and 1' tall...but a big crop, for a single person!). Ended up with enough potatoes, to fill a 16" cube box!!

To cure them, I utilized a pop-up plastic tent, designed to be used like a cold frame would be. I placed a couple old towels down, put the tent over them, then arranged the sweet potatoes on the towels, leaving some air space between them. Then I put in a small container of water, and suspended a small hand towel, from a string tied to the top frame of the tent, and the end of the rag in the container of water (like a wicking set up, to water a plant would work). Finally, I placed a small ceramic heater in the corner of the tent, to provide the heat required, and placed a combination thermometer/hydrometer inside the tent, where it could be easily read, by my unzipping only the top corner of the tent's "door".

Took a little bit of fine tuning, but in less than an hour, I had the inside of that tent at 85 degrees, and 85% humidity! Thinking back on it, I probably could have placed an old blanket over the tent, to help hold in the heat, and perhaps save a little bit of electricity.... but hey, it worked, as it was intended to!

And yeah, I'm STILL eating my way through those tubers!!

How ingenious! Gardeners are

How ingenious! Gardeners are so resourceful and creative! I’m going to try something similar. Curing has been a problem for me.

Growing sweet potatoes

Here in central Wisconsin I grow sweet potatoes in a raised bed. I cover the soil with plastic to help the soil heat up. Still have curly potatoes in various sizes. Haven't figured out why yet but I do have enough produce out of 18 plants to last the winter. Cure under the same white plastic loosely laid over the potatoes to protect them from any early frost. Next year hoping to use windows over the raised bed to form a small greenhouse. I'm from the south also so I understand you moms plight. Look into straw bed gardening. Its been a tremendous success for me. Good luck with your growing seasons!

Thanks for the advice and

Thanks for the advice and encouragement! I’m definitely going to stick with sweet potatoes until I get it right.


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