Growing Sweet Potatoes: An interview with Tom Witwicki, Master Gardener


One sweet potato with a green vine, with a grey backgroundDid you know that you can buy a single sweet potato from the grocery store and turn it into many pounds of food from the garden? Fascinating!

In this interview for our blog readers, Master Gardener Volunteer, Tom Witwicki describes sweet potato cultivation. He suggests that red garnet and Japanese purple are two varieties to try. “It’s quite an interesting process, unlike any other crop. They’re quite decorative,” he says.

Q. What are sweet potatoes?

A. A sweet potato is not like a regular potato at all. Regular potatoes belong to the nightshade [solanaceae] crop family. The sweet potato belongs to the morning glory family [dicotyledonous]. When it blooms, it has pretty little flowers that resemble a morning glory. Unlike the potato, the sweet potato doesn’t have toxic plant parts (like when potatoes get green). Since the sweet potato originated from the tropics of South and Central America, it requires heat and humidity to get started.


Q. How to cultivate sweet potatoes?

A. To cultivate sweet potatoes, it is ideal to use lighting, heat mats, and humidity domes.  “One common way to start sweet potato slips (which is what their ‘seeds’ are called) is to stick toothpicks in them and put them in cups of water. However, I prefer another method of putting them in a tray of potting mix. Either way you do it, vines will grow. Then, you break off the vine parts and put them in water to root. Next, to give them a head start, plant them in 4” pots to help establish the roots. -But don’t let them get root bound, which would twist the tubers! One slip can produce as much as 7-8 lbs of food.

Watch this video from last year of Tom growing sweet potatoes in the garden:

Gardener's hands in gloves, holding a string of sweet potatoes fresh from the ground in the garden

Q. How to harvest sweet potatoes?

A. When harvesting, wash them gently. The skin is fragile. They are not ready to eat right away. They won’t be sweet yet. The final step is a curing process. They need to be kept at a high temperature of 80-90 degrees and 80% humidity for about 8 days. People achieve this in Maine by storing them in a plastic bag out in the sun and spraying them with water. This toughens the skin and makes them sweet.

Q. Who can grow sweet potatoes?

A. Anyone can grow sweet potatoes at home, but keep in mind they do take up space. One row of sweet potatoes can cover an area of 4-5 feet in all directions. It’s not an ideal crop for a small community garden bed. Although, gardeners could experiment with vertical growing methods. You have to train the vines up and tie them because they don’t climb. The vines creep over the ground, which makes sweet potatoes a cool companion crop for taller crops such as brussel sprouts.

Curious to learn more?

Come to our May 18th Plant Sale! Tom will be there to lead a sweet potato growing demonstration. Shoppers will get a firsthand look at what “sweet potato slips” are. Ask questions and learn tips about how to grow this delicious vegetable!


Sweet potato chips in a dish with garnish
Sweet Potato Chips
Baked Sweet Potato Boats on a plate with sour cream, peppers, olives, and garnish.
Baked Sweet Potato Boats









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Master Gardener Plant Sale Postcard