Mainstay Vegetables: Sweet Potatoes

Wendy S. Delmater
By Wendy S. Delmater on Sun, Nov 3, 2013 - 5:21pm

Sweet Potatoes are often confused with yams in the United States and Canada but are twp distinct species. They are easier to grow than you'd think possible.

With care, early-maturing cultivars can be grown as an annual summer crop in temperate areas, such as the northern United States. First thing to know is your frost date since sweet potatoes cannot  tolerate frost. They grow best at an average temperature of 75 °F (24 °C), in full sun with warm nights.  Most take about 100 days to mature. If your climate has annual rainfalls of  30 to 39 inches (750–1,000 mm) or you can irrigate to get at least 20 inches of rain (500 mm) during your growing season, especially when they are setting tubers at about 60 days, why not give them a try? And sweet potatoes are resistant to almost all plant diseases (as long as they don't get waterlogged) so they are a great addition to an organic garden. Floating row covers may be required to discourage deer, though.

Sweet potatoes are grown on a variety of soils, but well-drained, light- and medium-textured soils with a pH between 5.8 and 6.2. They can be grown in poor soils  but will do a better with a little fertilizer, like about 2 cups of 5-5-10 over 30 sq ft. If you're going organic, that third fertilizer number, the potassium, is the important one: use greensand. Please note that sweet potatoes are very sensitive to aluminum toxicity and will die about six weeks after planting if lime is not applied at planting in this type of soil.

Sweet potatoes are propagated by stem or root cuttings or by adventitious roots called "slips" that grow out from the tuberous roots during storage. Space them about 12 inches apart in rows at least 3 feet apart, or 10 inches apart for biointensive plantings or raised beds. Because they are sown by vine cuttings rather than seeds, sweet potatoes are relatively easy to plant. When setting out sweet potatoes in very hot, sunny weather, you should cover the plants with upturned flower pots for 3 days after planting to shield them from baking sun. In the North it’s a good idea to cover the soil with black plastic or black fabric mulch about 3 weeks before planting to warm the soil. Remember, the rapidly growing vines shade out weeds, so little weeding will be needed. That's my kind of plant!.

Harvest when the vines start to die. Don't wash them before curing. (Note: uncured sweet potatoes are not as sweet and do not bake well.) Lay them out on a piece of cardboard or cloth in a well-ventilated place that is 80 to 90 degrees F--or a table outside in the shade if there is no rain--for 10 days. Unlike Irish potatoes, any scratches on sweet potato tubers should dry and "heal" so you can store the root.  After 10 days, move your cured tubers to any spot that stays cool and dry, but do not refrigerate or store them below 50°F. Cured sweet potatoes will keep for up to 6 months when stored at around 60°F with high humidity; a basement is ideal, and an air-conditioned storage room or pantry will work, too.


Wendy S. Delmater's picture
Wendy S. Delmater
Status: Diamond Member (Offline)
Joined: Dec 13 2009
Posts: 1988
a good place to buy sweet potato slips

A good place to buy sweet potato slips is Steele Plant Company. My father-in-law in Fairfax VA recommended them. He gets enormous yields.


kevinoman0221's picture
Status: Silver Member (Offline)
Joined: Sep 25 2008
Posts: 144
Thanks Wendy

This is great. I can't wait to try planting them.

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