Known botanically as Pachyrhizus erosus, this tropical American native is grown for its edible root, which resembles a large brown turnip and tastes something like a water chestnut. Twining or scrambling vines (to 14 feet high) are attractive, with luxuriant deep green foliage and pretty flower clusters. Leaves have three leaflets, each the size of a hand; upright spikes of sweet peashaped purple or violet blossoms appear in late summer. Flowers should be pinched out to encourage maximum root production, but you can allow seed for next year's crop to form on one or two plants. Needs a long, warm growing season and rich soil. Train on a trellis or grow on the ground as a trailing mound. Sow seeds after danger of frost is past, 11 inches deep and 612 inches apart, in rows 34 feet apart. Feed once or twice in early or midsummer with a high-nitrogen fertilizer. The edible roots will form as days begin to grow shorter; harvest them before the first frost. Each vine produces a single 1- to 6-pound taproot. Peel off the rough brown skin and eat the white flesh raw or cooked. Best suited to south Texas and south Florida.