In tropical and subtropical areas, yams are a better crop for the home garden than potatoes. The tubers have tough brown skins, while the flesh can vary in color from white to yellow to purple.
Dioscorea spp.
Originating in Asia, these root vegetables have become the staple carbohydrate in many tropical regions, including West Africa, the West Indies, and Asia. Plants grow as vigorous twining vines and produce large tubers with a bland flavor, best baked, steamed, or boiled.
In tropical and subtropical areas, yams are a better crop for the home garden than potatoes. The tubers have tough brown skins, while the flesh can vary in color from white to yellow to purple.
Yams grow well in the tropics and warm temperate regions where there is plenty of water throughout the growing season. They require soil rich in organic matter and will thrive in either full sun or semi-shade. Plant sprouting tubers as the ground warms up in spring. Being a vine, this plant will need a trellis or climbing frame for support.
Harvesting Tubers can be harvested when the vine dies back in autumn. As with all root crops, take care when lifting tubers to avoid damaging them. They store well in a cool, dry place for a number of months. Keep some tubers for replanting next season.
• Dioscorea alata—Greater yam, purple yam, white yam, water yam, winged yam, Guyana arrowroot
The vine produces extremely large, brown-skinned tubers with white or purple flesh and nutty flavor. Tubers reach 15–30 kg (30–60 lb) each.
• Dioscorea bulbifera—Aerial yam, air potato
In addition to tubers in the ground, it produces tubers in leaf axils on the vine that are large enough to harvest. It is less productive than Dioscorea alata, but plants can become weedy.
• Dioscorea cayenensis—African yellow yam, igname jaune
This is one of the main yam species grown in West Africa. The vine can grow to 10–12 m (30–40 ft), so it is not a good choice in small gardens. It is a cultivated yam available at farmers’ markets and Caribbean groceries.
• Dioscorea esculenta—Chinese yam, lesser yam, potato yam, cinnamon vine
The vine produces small tubers with fine hairs and deliciously cinnamon-scented flowers. This variety will tolerate cool climates as long as it is watered well over the summer.
Sweet potatoes are sometimes mislabeled as yams. True yams have rough skin, while sweet potatoes are smoother. Choose yams with unblemished skin and firm flesh. Store in a cool, dark cupboard at room temperature, not in the refrigerator. Once cooked, keep in the refrigerator for up to three days.
Wild yam (Dioscorea villosa) is used in East Indian traditional medicine as a remedy for sexual and hormonal problems. Chinese herbalists use wild yam for rheumatism and asthma, while Native Americans and early American settlers used it for colic and coughs. Despite an initial flurry of interest, researchers today say that wild yam creams do not provide hormones that help menopausal symptoms.
The edible, cultivated yams found in the grocery store do have health benefits. One cup (136 grams) provides a significant amount of vitamins B6 and C as well as 25 percent of the recommended daily intake of manganese. This important trace mineral is used by the body to manufacture sex hormones, connective tissue, bones, and blood-clotting factors.
In Africa, yam is pounded into a dough-like paste called fufu. It is rolled into balls, dipped in a soup or stew, and eaten by hand.
While yams can be substituted for sweet potatoes in recipes, true yams have an earthier, starchier taste and a drier texture than sweet potatoes. Yams go well with strongly flavored meats such as venison and are often served with spicy sauces. They can be roasted, added to stir-fries, made into chips, steamed, mashed or pureed. Always peel yam tubers first and always cook them well before eating.