Backyard Gardener: The sweet potato, a true tropical garden plant | News, Sports, Jobs


Hello, Mid-Ohio Valley farmers and gardeners. Still enjoying beautiful weather in May. It’s a busy time of year with graduations and schools ending for summer vacation. Congratulations to all of our graduates. My niece, Marlee Stollar, just got her master’s degree in agricultural communication from The Ohio State University. Like that girl.

Gardening season is in full swing as we transplant tomatoes and peppers and direct plant squash and sweet corn. It’s always a good idea to space out sweet corn plantings, so not everything is ready to harvest at once. Keep plant spacing in mind to get good sunlight and air circulation, especially with tomatoes and peppers. Although they need to be trained, green beans are very good yielders for a successful garden. If you can follow once they start producing.

If you have the space, sweet potatoes (Ipomea batatas) are fun to grow, big yielders, and very nutritious. They are high in fiber and vitamins A and C, making them a great addition to the vegetable garden.

A baked sweet potato (about 3 1/2 ounces) has only 141 calories (this doesn’t include butter, which makes a baked sweet potato taste great). They are also an excellent source of antioxidant beta-carotene.

Some interesting facts. The sweet potato is the official state vegetable of North Carolina, as its sandy soils are an ideal place to grow this root crop. In Japan, sweet potato juice is fermented to produce an alcoholic beverage called “shōchu”. During the American Revolutionary War, sweet potatoes were a food source for colonial troops.

The sweet potato is a true tropical plant. They are part of the morning glories family, unrelated to the Irish potato which is a nightshade. They have a tuberous root where Irish Potatoes are not roots but specialized underground storage stems called “tubers”.

Sweet potato is a warm season crop that should not be planted until the last chance of spring frost here in West Virginia. Soil temperature should be above 65F before planting.

Sweet potatoes are produced from plants or germs called “slip” produced from the roots of the previous season’s harvest and vine cuttings. You can grow your own cuttings, but many gardeners prefer to buy cuttings from a reputable nursery. If you need help, contact the office and we can refer you.

It’s cool to produce your own transplants or cuttings by litter “seed” potatoes you bought or saved from last year’s harvest. Pay attention to flesh, skin color, shape, and freedom from disease and insects with the potatoes you select to grow cuttings.

To produce your own cuttings, place sweet potato roots on their side in trays of soil six to eight weeks before transplanting them outdoors. Cover the roots with 2 inches of moist sand and keep the soil in the trays between 75 and 80 degrees F. When the sprouts are 4 to 6 inches long, pull them out with a twisting tug. Sprouts can be planted directly in well-prepared gardens or raised beds. A seed potato can produce 10 to 20 plants from several cuttings.

Be careful, sweet potatoes require a long growing season, 90 to 150 days. They also need deep, workable soil. Tight clay soils like the ones we have in West Virginia can produce misshapen potatoes, so till the soil and add amendments like compost or manure to loosen the soil.

Plants (slips) are planted three to four nodes deep (3 to 4 inches deep), 9 to 18 inches between plants in rows 36 to 48 inches apart. A knot is a bump or swelling on the slip where a leaf was attached. The orientation of the cuttings is not critical because the cuttings can be planted upside down and will still produce sweet potatoes.

Sweet potatoes should be planted on ridges or raised beds (6 to 9 inches high). Raised beds promote root development and improve soil drainage and aeration. Sweet potatoes do not tolerate waterlogged soils. Sweet potatoes tolerate acidic soils and the pH can be 5.0-6.5 for successful growth.

Another good tip. Transplanting conditions are important for success. If poorly rooted cuttings are planted in sunny, hot conditions, many may wither and die before the roots can establish themselves. It is best to wait until the weather is overcast and ensure that the water soaks in immediately after planting.

Let’s talk varieties. Popular orange-fleshed varieties include Beauregard, Covington, Jewel, Georgia Jet, and Puerto Rico. These vary in root size, uniformity, and days to maturity. The color of their skin and flesh also varies slightly. Bonita, White Hamon and O’Henry have cream colored flesh. The Japanese violet has purple skin and white flesh. All-purple varieties have purple skin and purple flesh.

Beauregard is a standard for Mid-Ohio Valley gardeners. Covington is also a good improved variety and is quickly becoming the standard crop in the top sweet potato producing state, North Carolina.

Sweet potato production is not perfect. Deer love sweet potato foliage and graze it down to the ground. Although this will not kill the plants, it will significantly reduce yields. Be careful with fertilization. Overuse of nitrogen with sweet potato plants only results in foliage and poor root development. Weeds are perhaps the biggest problem when growing sweet potatoes, as the vines quickly spread through the garden.

Wireworms and root-knot nematodes seem to be the biggest problems for home gardeners. However, many insect and disease problems can be avoided by choosing disease-resistant varieties and using good cultural gardening practices. Crop rotation with a vegetable from another family can help prevent nematodes and soil diseases.

Sweet potatoes can be harvested any time after the hills have produced usable potatoes, usually 90 to 120 days after the varieties are transplanted. They should be dug as late as possible in the fall, but before a hard frost. The vines can tolerate light frost, so it can be helpful to mow and remove the vines before digging, to make root access easier.

Most of the grading takes place in the last two to three weeks, so keep a close eye on pruning to time the harvest before the potatoes get too big. However, too much soil moisture at this time can cause root rot before harvest or cracking of potatoes after harvest.

When harvesting, handle sweet potatoes with care to avoid bruising. They are more fragile than the Irish potato due to their thin skin. After digging, the potatoes should be “cured” placing them in a warm place (80-85F) for four to seven days. This heals any wounds on their skin and increases shelf life.

Do not store them in the refrigerator. Roots are easily damaged by temperatures below 50F. Sweet potatoes should be stored in bins in moderately warm (55-60F) and humid conditions in a cool, dry place. Contact me at Wood County WVU Extension Office 304-424-1960 or email me at [email protected] with questions. Good luck and happy gardening!

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