Adapted from an article by Joseph Masabni and Stephen King Assistant Professor and Extension Horticulturist, and former Associate Professor, Texas A&M Department of Horticultural Sciences The Texas A&M University System
Sweet potatoes (Ipomoea batatas) are a member of the morning glory or Convolvulaceae family. The plant produces colorful flowers as well as trailing vines often used as groundcovers.
The sweet potato is a perennial plant (one that lives for more than 2 years) originating in the tropical Americas.
Hot days and warm nights are ideal for sweet potato production, which is why Texas is a large sweet potato producer. Sweet potatoes are extremely heat tolerant. They can also tolerate light frosts as long as the soil temperature stays above 13°C.
Figure 1. Leafy vines of the sweet potato plant.
Sweet potatoes require full sun and a warm climate. They must be planted in a well-drained, fine sandy loam soil with a slightly acidic pH 5 to 7.5. This allows the sweet potato to grow easily but not remain in a moist environment that encourages rot and disease.
Add compost into the soil. This will be the only fertilizing needed. Work the soil into beds 20cm high and 3 to 4 feet apart to ensure that it drains well and warms quickly in early spring (Fig. 2).
Figure 2. Soil beds 20cm high and 90 cm wide.
Unlike other vegetables, sweet potatoes are propagated from slips, also called vine cuttings. Slips can be produced at home, purchased at a local garden store, or ordered from online companies.
To produce slips, buy healthy, disease-free sweet potatoes from a local market. Scrub them clean and then cut them in half. Suspend each half over a jar of water by inserting toothpicks so that half is submerged in the water. Place the sweet potato near a window for warmth and sunlight. Over the next few weeks, shoots will form on top (Fig. 3).
Wait 2 weeks after the last frost to begin planting them outside.
Figure 3. A sweet potato producing slips.
The optimal planting time is when the soil temperature at planting depth is over 18°F in the spring and at least 150 days before it gets cold in the winter.
Keep the beds weed free until the vines have covered the soil fully. Maintaining a weed-free area, especially in the first 40 days after planting, will improve yield quantity and quality at harvest.
Sweet potatoes need about 500L of water per plant per season. Because rain falls sporadically throughout the season, you will need to water them, especially at first during the slip establishment period. Transplanted slips are extremely sensitive to water stress during the first month of establishment.
To keep the tubers from rotting, do not water in the last 2 to 3 weeks before harvest.
Diseases and insects
Sweet potatoes are attacked by leaf spots, nematodes, beetles, cutworms, and weevils. (Table 1).
TABLE 1. Sweet potato pests and controls
The sweet potato root has a delicate skin that is easily bruised at harvest. Take care not to bruise the roots with a hoe, shovel, or other harvesting tool. Even dropping the potatoes into a harvest bucket will injure the skin.
For home gardeners, the best time to harvest sweet potatoes is immediately before or just after the first fall frost. When the sweet potato leaves turn yellow, growth has stopped and the roots have matured. This is a good time for harvest.