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How to Grow Sweet Potatoes in the Home Garden

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Baskets of fresh sweet potatoes for sale Joe Fox/Photographer's Choice RF/Getty Images

Overview:

Although the terms sweet potatoes and yams (Dioscorea sp.) are used interchangeably in the U.S., they are two entirely different vegetables. They are also unrelated to regular potatoes. Sweet potatoes are in the same family as Morning Glories (Ipomoea tricolor) and you’ll easily see the similarity in leaves to the sweet potato vines we now grow as ornamentals. Although sweet potatoes require 4 months of warm temperatures to develop full size tubers, they are surprising easy to grow.

Latin Name:

Ipomoea batatas

Common Name(s):

Sweet Potato, Yellow Yam

Hardiness Zones:

Annual Crop

Mature Size:

Depends on variety. Vines can easily spread 20'. Tubers average about 4-6".

Exposure:

Full sun to Partial Shade. They generally prefer full sun, but appreciate some afternoon shade in hot, dry regions.

Days to Harvest:

Harvest roots in 4 months. Harvest leaves throughout season.

Description:

Sweet potatoes are the tuberous roots of vining plants. These vines root wherever they touch the ground and can produce a generous harvest. There are also bush varieties, for smaller gardens.

The orange fleshed sweet potatoes are the most familiar, but sweet potatoes can be white, yellow and even purple.

Suggested Varieties:

  • Beauregard - Pale reddish skin with dark orange flesh. Popular commercial variety. (100 days)

  • Bush Porto Rico - Cooper skin with orange flesh. Compact vines with big yields. Good for smaller gardens, (110 days)

  • Centennial - Good disease resistance and relatively quick maturing. (90-100 days)

  • Georgia Jet - Reddish skin with orange flesh. Good choice for shorter season. (90 days)

  • Patriot - Copper skin/Orange Flesh. Great pest resistance. Good choice for organic gardens. (100 days)

  • Ruddy - Better pest resistance (insects, diseases and nematodes) than Beauregard. See photo. (100 days)

Harvesting:

You can dig your tubers once the foliage starts to yellow. If the foliage is hit by a frost, the tubers are probably still fine. Just don’t let them sit in the ground too long after the tops die back.

Be gentle when digging. Sweet potato tubers grow close to the surface. Their skins are tender and can be damaged and bruised easily.

Growing Tips:

Soil: Sweet potatoes like a slightly acid soil, prefering a soil pH between 5.0 and 6.5.

What to Plant: Sweet potatoes are usually grown from slips; small rooted pieces of tuber. You can create your own slips by slicing a sweet potato in half lengthwise and placing it on a bed of damp potting soil. Cover the pieces with a few inches of soil and keep moist and warm. Small roots should develop within a few days, followed by leaves. They are ready to be lifted and planted once they’re about 4 - 8 inches tall. (About 6 weeks.) You can try growing sweet potatoes from the grocery store, but the only way to be certain you have certified disease-free roots is to buy them from a reputable seed supplier.

If you have a short winter, you can begin new slips from vine cuttings. Snip off about 6" from the tips of the vines, before frost. Place these cuttings in water. Once they develop roots, plant in soil and keep them in a sunny location until it’s time to plant them outdoors.

When to Plant (Transplanting): Plant sweet potato slips as soon as the ground has warmed and all danger of frost has passed. To give them a head start, sweet potatoes are often planted in raised rows, about 8" high. This helps the soil warm faster and keeps them well drained. If you are gardening in a cooler climate, spreading black plastic on the soil will also help it warm faster.

Spacing: Space plants about 12 - 18" apart with 3 - 4' between rows. The vines will spread and fill in, so give them plenty of room.

Feeding: Feeding sweet potatoes tends to produce just foliage. Plant in a soil high in organic matter and then leave them alone.

Tip: Don't water your sweet potatoes during the final 3-4 weeks prior to harvest, to keep the mature tubers from splitting.

Maintenance:

Sweet potatoes can be slow starters and they don’t like to compete with weeds. Keep the area clear until the top growth fills in and acts as a natural mulch.

Sweet potatoes can tolerate periods of drought, but regular watering is the best way to prevent splitting.

Pests & Problems:

Wireworms and root-knot nematodes are the biggest problems in home gardens. Damage is lessened if you rotate your crop each year.

Many diseases can be avoided by choosing disease resistant varieties and using certified disease free seed sweet potatoes. Rotating their location in the garden, from year to year, also helps.

Mice can also be a problem, so be on the lookout.

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