Sweet potatoes are a marvelous garden crop – from one planting two nutritious, edible harvests are produced. Sweet potato tubers have some of the highest Vitamin A content of all vegetables and stems and leaves are packed with nutrients.
Not only are sweet potatoes super nutritious, they also make an exceptional rotation crop as they are a member of the Convolvulaceae, or morning glory, family; if the greens are not wanted as an edible, they make a terrific organic amendment when tilled into the soil at the end of the season.
The specific epithet of sweet potato, Ipomoea batatas (ih-pom-OY-ee-ah ba-TAH-tas), comes from the Greek ips, which means “worm” and homoios that means “resembling”. The species name batatas, is the Haitian name for sweet potato that reflects its Central and South American origin.
Sweet potatoes are tuberous, tender perennials. They are one of the last crops of the summer garden to be harvested since tubers require up to 120 frost-free days to mature.
The usual crop harvested from sweet potato plants are tubers, but the greens are also edible and delicious. Leaves grow on slender, prostrate stems and are a powerhouse of nutrition, containing omega-3-fatty acids, vitamins A, C, K, B complex; minerals calcium, iron, magnesium, phosphorus, potassium, and zinc (horticulture.ucdavis.edu). Greens can be eaten as a fresh salad crop, but are best when lightly steamed, sautéed, or in stir fry. When cooked, leaves have a soft texture and are milder than kale or Swiss chard.
Tubers are ready to be harvested when leaves start to yellow, an indication of maturity. Wait to dig tubers until just before a freeze is expected; yields and nutrients increase the longer tubers stay in the ground. Tubers can withstand a light zing of 32°F but are damaged with a freeze; tops will blacken and be damaged by a light frost.
Harvest using a digging fork. Gently lift soil a good foot away from the base of the vine since tubers develop a distance from the mother slip. Dig straight down a foot or more under the base of the vines. Gently lift clumps, loosening soil from tubers. Cut tubers from mother slips using sharp pruners, never pull out of the soil or tear away from vines as tubers are easily injured.
Dig tubers when soil is slightly dry. Wet soil clings to tubers and is difficult to clean. Do not wash tubers. Cull damaged tubers, reserving these as the first to be eaten.
Curing is the key to longevity; also, during curing the sweetness of tubers increases. Skin heals during curing, reducing infection from pathogens. Wrap tubers in tissue paper and store without neighbors touching in a dark, humid, warm, well-ventilated place for about 10 days. Tubers can be enjoyed for months if properly cured and stored store between 55 and 60°F.
Ellen Peffley taught horticulture at the college level for 28 years, 25 of those at Texas Tech, during which time she developed two onion varieties. She is now the sole proprietor of From the Garden, a market garden farmette. You can email her at gardens@suddenlink.net