Harvesting, Curing, and Storing Sweet Potatoes

Harvesting, Curing and Storing Sweet Potatoes

Sweet potatoes are warm-season plants in the morning glory family that are sensitive to cold temperatures. The part we eat is the fleshy root of the plant, a little different than the regular plain potato, which is a fleshy underground stem or rhizome of the plant, called a tuber.  Although sweet potato roots continue to grow until frost kills the vines, an extremely hard frost can cause damage to the ones near the surface. Chilling injury also results when soil temperatures drop to 50°F or lower, and this can result in internal decay in storage. The greatest danger from delayed digging is the risk of cold, wet soil encouraging decay. So if you haven’t already harvested, now is the time.

Although you can cook newly dug sweet potatoes right away, their flavor and storage quality is greatly improved by curing at warm temperatures first. It is during the curing process that starch is converted to sugar.

Cure sweet potatoes by holding them for about 10 days at 80-85°F and high relative humidity (85-90 percent). Commercial producers have temperature and humidity controlled housing to guarantee good results, but for the home grower, they can be cured near a furnace or heat source to provide the necessary warmth. If the temperature near your furnace is between 65-75°F, the curing period should last 2-3 weeks. To maintain the required high humidity (85-90 percent relative humidity), stack storage crates or boxes and cover them with paper or heavy cloth. Packing in perforated plastic bags will also keep humidity high, yet the perforations will allow excess moisture to escape.

Ornamental Sweet Potato Vines

Have you ever wondered what, if any, is the difference between the ornamental sweet potato vines grown as a season-long ground cover, or, as “spillers” in container arrangements, and the vegetable we grow as food?  The answer is – not much.  They are just different cultivars of the same species, Ipomoea batatas.  The ones we grow for food are selected and bred to produce large, uniform, good tasting roots, high in nutrients for eating, whereas the ones we grow ornamentally are selected for the striking shapes and colors of their leaves, ranging from the bright chartreuse green of ‘Marguerite’ to the black, ‘Blackie’ and even a multicolor ‘Tricolor’ cultivar.  Plant breeders introduce new variations every year.  If you dig up the earth around your ornamental vines, you’ll find the same fleshy roots (different colors, perhaps) as the familiar ones we grow, or buy, for food.  So, can you eat them?  Well, technically, yes – but there’s no guarantee how they’ll taste.  In addition, rules for pesticide use on plants grown for eating are stricter than those on plants grown for looking, so Penn State Extension does not recommend you eat them.  However, if you dig, cure, and store them as above, it’s possible they can stay viable until spring, when you can try to continue their growth for another season by suspending them with toothpicks ½ submerged in a glass of water until sprouts appear.  You would do this around mid-March or so.  Cut the stems of the sprouts (called slips) after they’re about 6-8 inches long, with about 6-8 leaves and root them in a glass of water.  Place in a warm, sunny spot until you can see the roots grow, periodically changing the water.  Plant in the ground, or container, after all danger of frost is past, sometime in mid to late May.  Or, if that seems like too much work, appreciate the efforts of your local greenhouse grower and support them by purchasing your slips next year.  There will probably be a new color you’ll want to try, anyway.