Row by Row Episode 200: How To Grow Sweet Potatoes

What is a sweet potato? Even though sweet potatoes originated from Central and South America (the same as potatoes), they are not related to potatoes. Sweet potatoes belong to the bindweed or morning glory family. Let’s do a deep dive into all things about how to grow sweet potatoes.

How To Grow Sweet Potatoes – Fun Facts

  • This tropical crop needs at least four months of warm weather and warm soil, but they are drought- and heat-tolerant and have few pests or diseases.
  • Compare a sweet potato vine’s foliage and flowers to those of morning glory and you’ll see the family resemblance.
  • Sweet potatoes are not yams, which are related to grasses and lilies. They’re also not related to regular white potatoes, which belong to the nightshade family, versus the morning glory family. As mentioned above, potatoes’ edible portion is a true tuber, while sweet potatoes produce tuberous roots.
  • They were used in folk remedies to treat asthma, night blindness, and diarrhea.

Recommended Varieties

The fastest-growing sweet potato varieties have orange flesh, but you might also consider varieties with white, yellow, or even purple flesh. Note that orange-flesh varieties cook up moist; white and yellow sweet potatoes become creamy; purple sweets are dry and starchy.

  • ‘Beauregard’ (90 days) originally comes from Louisiana but grows well in the north, too. It has dark red roots, and dark orange flesh, and stores well.
  • ‘Bush Porto Rico’ (110 days) is good for small gardens and for baking.
  • ‘Centennial’ (100 days) is the leading variety in the U.S. It is carrot-colored and has a good storage life. It is also a good producer for northern growers.
  • ‘Georgia Jet’ (90 days); Red skin covers moist, deep orange flesh. Extremely fast-growing type; good for the North.
  • Jewel’ (aka ‘Yellow Jewel’)(120 days) has copper-colored skin and orange flesh; disease-resistant; stores well.
  • ‘Stokes’ (120 days) offers vibrant purple color and is full of extra health benefits; cooks well in savory dishes and mashes.
  • ‘Vardaman’ (110 days) is a bush type and good for small gardens; it has unique blue/purple foliage, golden skin, and reddish-orange flesh; stores well.
  • ‘White Yam’ (100 days); also called ‘White Triumph’. White skin covers dry white flesh. One of the oldest sweet potato varieties. Has compact vines.

When To Plant

  • Plant slips outdoors 3 to 4 weeks after your last spring frost or once the soil has warmed to at least 65°F (18°C). Nighttime temperatures should be at least 55°F (13°C). The trick is to plant them early enough for them to have time to mature fully, but not so early that they get killed by a late spring frost.
  • Be sure to protect young sweet potatoes from any late frosts or cool nights (lower than 55°F/13°C), as they are very tender. Cover them with plastic milk jugs or use row covers, removing the covers during the day.
  • If you ordered slips from a mail-order source, unpack them right away. Stick the roots in water for a day or so and they’ll perk up. Plant them as soon as conditions are right

How To Plant

  • Plant the slips on a warm, overcast day, when the soil temperature has reached 60°F (15°C).
  • Break off the lower leaves, leaving only the top ones.
  • Set the slips deep enough to cover the roots and the stem up to the leaves. Sweet potatoes will form on the nodes.
  • Water with a high-phosphorus liquid fertilizer, then water generously for 7 to 10 days to make sure that the plants root well.

Common Pest and Diseases

  • Flea beetles: Numerous tiny holes in leaves. Use row covers; mulch heavily; add native plants to invite beneficial insects
  • Fusarium wilt: Yellow/puckered leaves; older leaves drop; wilting vines; plants eventually die; stems under-/near ground may appear slightly blue; stem cross-section reveals brown/purple/black discoloration, especially near ground      Destroy infected plants; choose certified, disease-free slips and resistant varieties; rotate crops
  • Sweet potato scurf: Skin-deep, dark brown/black spots or blotches on root tuber that may enlarge in storage; roots may shrivel; reduced shelf life   Choose certified disease-free plants or use vine cuttings or sprouts cut at least 1 inch above soil line; disinfect tools and storage containers; rotate crops
  • White rust: Chalk-white blisters mainly on leaf undersides; small, yellow-green spots or blisters, sometimes in a circular arrangement, on upper leaf surfaces; possible distortion or galls; flowers/stems may also be infected   Destroy infected plants; choose resistant varieties; weed; destroy crop residue; rotate crops
  • Whiteflies: Sticky “honeydew” (excrement); sooty, black mold; yellow/ silver areas on leaves; wilted/stunted plants; distortion; adults fly if disturbed; some species transmit viruses   Remove infested leaves/plants; use a handheld vacuum to remove pests; spray water on leaf undersides in morning/evening to knock off pests; monitor adults with yellow sticky traps; spray with insecticidal soap; invite beneficial insects and hummingbirds with native plants; weed; use reflective mulch

Harvesting

  • Harvest when the leaves and ends of the vines have started turning yellow or about 100 days from planting. The longer the crop is left in the ground, the higher the yield
  • Loosen the soil around each plant (18 inches around, 4 to 6 inches deep) to avoid injuring the roots. Cutaway some of the vines.
  • Pull up the plant’s primary crown and dig up the roots by hand. Handle the sweet potatoes carefully, as they bruise easily.
  • Shake off any excess dirt; do not wash the roots.
  • Dry in sun for several hours, then move to a well-ventilated spot
  • Complete harvesting by the first fall frost.

How To Cure And Store

  • Curing sweet potatoes gives them that sweet taste and also allows a second skin to form over scratches and bruises.
  • Handle sweet potatoes carefully; they bruise easily.
  • To cure, store roots in a warm place (about 80°F) at high humidity (about 90%) for 10 to 14 days. A table outside in a shady spot works well. Arrange sweet potatoes so that they are not touching.
  • After curing, discard bruised sweet potatoes, then wrap each one in the newspaper.
  • Carefully packed in a wooden box or basket. Store in a root cellar, basement, or the like with high humidity at 55° to 60°F.
  • The roots should last in storage for about 6 months.

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