Yardlong beans are an annual, vining or bushy, subspecies of Cowpea (Vigna unguiculata) that produce elongated pods up to 1 m long. Green pods and seeds are eaten as a fresh vegetable and the plants are also used as fodder, green manure, or cover crop.
Asparagus Beans/Yard Long Beans probably originated in southern China.
The Yard Long Bean is reported to be one of the top ten vegetables in Southeast Asia, especially in Taiwan, southern China, and Bangladesh. It is the most widely grown legume of the Philippines where it is known as “poor man’s meat.” Bush Sitao (a cross between Yard long Bean and Cowpea) reportedly is replacing Yard Long Bean as a favorite in the Philippines. It is bush-shaped, doesn’t need a trellis, and is less susceptible to wind damage than Yard long Bean. Yard Long Bean has been introduced to many lowland tropical countries where often it is a minor garden vegetable. It has become popular in the Caribbean and is grown as a summer crop in California and in parts of Europe, especially as a greenhouse vegetable.
Yard Long Beans are annual plants propagated by seeds. To germinate well the soil should be warm (20-22°C/68-72°F) at planting, otherwise the seeds likely will rot. Yard Long Beans thrive in hot humid climates. Environments with full sunlight attaining daytime temperatures of 25-35°C (77-95°F) with nighttime temperatures not falling below 15°C (59°F) are preferred. Yard Long Beans will grow and produce poorly in the mid-elevation tropics or in temperate climates. Yard Long Beans are climbers. Plant in hills or in rows for pole or trellis growth. Newer bush varieties do not require trellis or pole constructions, however. Thin hills of 5-6 seedlings to 3 plants per pole after emergence. Provide loose nutrient-rich soil. Fertilize with a balanced fertilizer as needed but avoid the use of high-nitrogen fertilizers that will encourage excessive vine and foliage growth but retard flower and fruit production.
Harvesting and Seed Production
Yard Long Beans begin flower production 5 weeks after planting; fruit production begins 2 weeks later in warm humid climates. Harvest pods frequently (at least weekly). Pick the pods while they’re still tender before the seeds fill out the pods. Older pods become tough and unsuitable for eating. Matured pods contain reddish-brown seeds that may be sun-dried on racks for storage.
Pests and Diseases
Yard Long Beans are damaged by rust and mildew diseases as well as by cowpea virus diseases such as cowpea aphid-borne mosaic virus and cowpea witches’ broom virus. Virus control is aided by destroying infected plant materials and by control of aphids, whiteflies, leafhoppers and beetles that serve as virus vectors. Yard Long Beans often are relatively pest-free compared to Green Bean varieties; however, the bean shoot fly and the bean pod fly may hamper plant growth and pod production. Remove and burn damaged plant materials to prevent spread of pest species.
Cooking and Nutrition
Yard Long Bean is grown chiefly for the long immature pods that resemble French green beans in flavor. The raw pods reportedly have a mushroom-like flavor. Some users claim an asparagus flavor for them, as reflected by the name, “Asparagus Bean.” The mature seeds may be dried for storage and later cooked as a pulse. Young leaves and stem tips are eaten steamed as a vegetable.