Yardlong Bean

Yardlong bean is a vigorous twining annual with trifoliate leaves and pale violet or white flowers. Its pods hang in pairs and typically grow 30 to 90 centimetres long, although they are only about a centimetre wide, and are green, pale or sometimes purple-red. The pods are picked young, while still tender, before the seeds swell. If left to mature, each pod holds a row of kidney-shaped seeds that are red, brown or black. The pods taste like a mild, slightly earthy green bean, with a firm texture that holds up in cooking.

The yardlong bean is a cultivated subspecies of the cowpea, Vigna unguiculata, a crop domesticated in Africa. It is thought to have been developed by selection in Asia, probably in southern China or Southeast Asia, from cowpeas introduced there centuries ago, where very long, tender-podded forms were selected. It is now widely grown in southern China, Taiwan, Thailand, Vietnam, Indonesia, Malaysia, India, the Philippines and the Caribbean, and also by immigrant communities in Africa, North America and Europe.

Cowpeas reached Asia early in agricultural history, and the long-podded form gradually became an important vegetable in warm, humid regions where common green beans do not grow as well. In Chinese farming texts and cookery it has long been used for its tender, bean-like pods, and it became a favourite in tropical gardens because it tolerates heat, rain and poor soil better than snap beans.

Today it is cultivated commercially as well as in home gardens, and trellised vines are a common sight in Southeast Asian markets and backyards. Seeds are exported by seed companies to Western gardeners seeking heat-tolerant beans, and in the US and Europe the pods are sold fresh in Asian grocery stores. Research programmes in tropical Asia are working to develop varieties with better disease resistance and yield.

The pods are cut into short lengths and stir-fried with garlic, chilli and shrimp paste, curried, steamed, pickled or eaten raw with dipping sauces, as in Thai and Lao cooking. In Chinese cooking they are stir-fried with minced pork or fermented black beans. In Indonesia and Malaysia they are served in salads such as gado-gado and pecel. Mature seeds are boiled or used in soups and stews, and the young leaves are sometimes eaten as greens.

Yardlong bean pods are low in calories and provide fibre, plant protein, vitamin C, folate, vitamin A precursors and potassium. Like other legume vegetables, they are a nutritious addition to meals. The mature seeds, like other cowpeas, are higher in protein and carbohydrate. Cooking improves digestibility and flavour. Nutrient values vary between varieties and pod maturity, and the figures given are approximate for raw pods.