Common names: potato, sweet potato, yam

Botanical name: Ipomoea batatas

Origin: tropical America and Caribbean

Varieties

Centennial (150 days); Goldrush (140 days); Jasper (150 days).

Description

The sweet potato is a tender vining or semi-erect perennial plant related to the morning glory. It has small white, pink, or red-purple flowers and swollen, fleshy tubers that range in color from creamy-yellow to deep red-orange. There are ''dry'' and ''moist'' kinds of sweet potatoes, which describes the texture when they're eaten; some dry varieties have a higher moisture content than some moist ones. The moist varieties are often called yams, but the yam is actually a different species that is found in tropical countries. Sweet potato vines are ornamental, so this vegetable is

often grown as ground cover or in planters or hanging baskets. You can even grow a plant in water in your kitchen - suspend the sweet potato on toothpicks in a jar of water, and watch it grow.

Where and when to grow

Sweet potatoes are extremely sensitive to frost and need warm, moist growing weather. They have a long growing season - about 150 days - and in areas with a shorter growing season, tend to produce small potatoes. Don't try to hurry sweet potatoes; plant them four weeks after the

average date of last frost for your area, or when the soil is thoroughly warm.

How to plant

Sweet potatoes are planted from rooted sprouts, or slips, taken from a mature tuber. To grow your own slips, place several sweet potato roots about an inch apart in a hotbed and cover with two inches of sand or light soil. Add another inch of soil when the shoots appear, keep the bed at a temperature between 70* and 80*F, and don't let it dry out. In about six weeks you will have rooted slips that can be planted in the garden. A good, sandy soil is best for sweet potatoes. Over-rich soil produces luxuriant vines but small tubers. The soil should be moderately fertile, rich in organic matter, and well-worked to ensure looseness. Remove all soil lumps, rocks, or other obstacles that might cause deformity of the tubers, and work in a complete, well-balanced fertilizer at the rate of one pound per 100 square feet or 10 pounds per 1,000 square feet. For good tuber production sweet potatoes must have full sun; in partial shade the vine will be handsome but not very productive. Set the slips on ridges made by mounding up the soil about eight inches high along rows three feet apart. Make the ridges about 12 inches wide, and set the slips at 12-inch intervals.

Fertilizing and watering

Fertilize before planting and again at midseason, at the same rate as the rest of the garden. If the soil is too wet, the roots of sweet potatoes may rot; in well worked, loose soil this should not be a problem. Although sweet potatoes will survive dry seasons, the yield is much higher if they get an inch of water every week until three or four weeks before harvesting. Do not water during the last three or four weeks.

Pests

Insects and diseases are not much of a problem in the North. In the South, sweet potato weevils and wireworms are common pests. The damage they do appears in the form of stunting or weakening of the plants. Both pests can be controlled by a soil drench of Diazinon.

Diseases

Fungus diseases and root rot may attack sweet potatoes. Planting disease-resistant varieties and maintaining the general cleanliness and health of your garden will help cut down the incidence of disease. If a plant does become infected, remove it before it can spread disease to healthy plants.

When and how to harvest

The tubers are damaged by freezing or cold soils, so dig up sweet potatoes early rather than late, before the first frost. Be careful when you dig - these potatoes are thin-skinned and bruise easily.

Storing and preserving

Cure sweet potatoes in crates in a dark, humid place for 10 days at 80* to 85*F; then store them at 55* to 60*F in a moderately moist place for four to six months. You can also freeze, can, or dry them.

Serving suggestions

Sweet potatoes are very versatile; you can boil, steam, fry, or bake them, and they take well to either sweet or savory seasoning. Use pureed sweet potatoes in bread or cookies. Candy them, or stuff them and bake them in their skins, include slices of raw sweet potato with the vegetables for a tempura. Cinnamon, cloves, nutmeg, and allspice all go well with sweet potatoes.