Phaseolus coccineus aka Runner Bean

Phaseolus coccineus is the runner bean, or scarlet runner bean. It belongs to the pea and bean family, Fabaceae. Its native range runs from Mexico to Nicaragua. Wild plants grow near forests, streams, and open wooded ground. People grow it for food in warm and cool regions. It also serves as a flowering garden climber.

This fast-growing vine climbs by winding its stems around supports. Garden plants reach about 8–13 feet [2.5–4 metres]. They spread about 3–5 feet [1–1.5 metres]. Some accounts report stems reaching 23 feet [7 metres]. A tuberous rootstock can support fresh stems each year. In Britain, gardeners grow it as a summer annual. Its green leaves fall at the season’s end. The foliage has a coarse texture, and stems lack scent.

Scarlet flowers give the plant its best-known common name. Some plants bear white blooms instead. Flowering runs from June to October, or until frost. Each flower lasts just one or two days. Bees pollinate the flowers, which also draw hummingbirds. The plant can set seed with its own pollen. Long, flat pods follow the flowers. Pods start green and may later turn purple. Seeds can be black with red markings. Heat above 90°F can make the pollen fail.

Grow runner beans in full sun with a firm support. They need moist soil that drains well. They accept clay, loam, sand, and chalk soils. Near-neutral soil suits cultivation, though the listed pH range is broad. Sow seeds outdoors once the risk of frost has passed. The RHS rates the plant H2, so freezing threatens growth. Missouri Botanical Garden lists USDA zones 7–11. No pruning is needed. Use trellises, fences, tripods, or pergolas to support the stems. Plants also suit containers, food gardens, and wildlife gardens. Their roots help add nitrogen to the soil.

Young pods and seeds provide food when cooked. The flowers are edible too. Mature seeds need thorough cooking to make them safe. Raw or poorly cooked beans can cause vomiting and diarrhoea. The RHS also warns that raw pods and beans harm dogs. No medicinal uses are recorded. Serious pest problems are not usual, but several can occur. Slugs, snails, aphids, and beetles may damage plants. Rust, mosaic virus, bacterial blight, and anthracnose can affect growth. Powdery mildew and white mould are further risks.