Pachyrhizus erosus aka Yam Bean

Pachyrhizus erosus is jicama, also known as yam bean. This climbing plant belongs to the pea family, Fabaceae. Its native range runs from Mexico through Central America. It grows along forest edges and in scrub. Its home climate has wet and dry seasons. Growers now raise it across many tropical regions. It has also spread into southern Florida and Hawaii.

The plant lives for several years in warm climates. Each year, its thick rootstock sends out twining stems. These can climb or trail across the ground. Tropical Plants gives stem lengths of 7–20 feet [2–6 metres]. Missouri Botanical Garden reports longer vines, reaching 20–30 feet [6–9 metres]. Its listed garden spread reaches 25 feet [7.62 metres]. Leaves grow in an alternate pattern along the stems. Each leaf has three leaflets. The flowers are showy and scented, and seedpods follow them. The evidence gives no fixed month for bloom.

Jicama needs full sun and a long, warm growing season. It grows best in light, rich soil that drains well. Missouri Botanical Garden lists its water needs as moderate. It survives winters outdoors in USDA zones 10–12. In colder places, gardeners can raise it as an annual. Seeds can start indoors four to six weeks before the last frost. Plant outdoors once frost has passed and soil has warmed. A good-sized root may need nine months of growth. Short growing seasons can leave small roots at harvest.

Most gardeners grow jicama for its swollen, turnip-like roots. A trellis can also show off its leaves, flowers, and pods. The roots have sweet, juicy flesh with a crisp bite. People eat them raw or cooked. Cut roots keep their colour and remain crisp after cooking. Their starch also goes into puddings and custards. Harvesting before full maturity avoids roots that have become fibrous. Soil bacteria in root nodules help the plant fix nitrogen. Growers also use it as green manure.

Missouri Botanical Garden reports no major pest or disease problems. Food safety still needs care: the edible root differs from the toxic tops. Leaves, seeds, and mature pods contain poisonous compounds. Keep the plant's upper parts away from children. Some sources list cooked young pods as food. This conflicts with broader warnings about all above-ground parts. The plant also contains rotenone, which has insecticidal uses. Such compounds can harm beneficial insects, fish, and amphibians.