Chinese Long Bean, Yard-long Bean, Asparagus Bean

 

Vigna unguiculata subspecies sesquipedalis is a member of the Fabaceae (pea) family.

Chinese long bean is an annual climbing plant. A cousin to the cowpea or black-eye pea, Chinese long bean is much more of a trailing, climbing variety, and often reaches heights of 9-12 feet. The pods grow to 12 to 30 inches long. The plant has large yellow to violet-blue flowers. It is an indeterminate plant, meaning it continues to grow after flowering and fruiting.

Other names. Taao-hla-chao (Hmong); juro-kusasagemae (Japanese); dow gauk (Chinese); sitaw (Filipino); dau-dau (Vietnamese).

Marketing. It is easy to make long beans look bad, in other words, old, dry beans look terrible.

San Francisco wholesale market prices for 1987 and 1988 are shown in Charts 1 and 2. These are weekly high and low market prices obtained in San Francisco. For both years supplies came from Mexico from mid-November through mid-June at which time supplies were from California. In the summer of 1987 prices typically ranged from 65 to $1.00 per pound. There was more variation in the summer of 1988, with low prices going down to 25 per pound. The highest prices were reached in January and February 1987, $2.75 to $3.00 per pound. Prices of $2.00 to $2.50 per pound were obtained from January through April in 1988.

Current production and yield. Chinese long beans are available year-round from the Caribbean, Mexico and California. Peak supplies are in the late summer or early fall. In a field test at Riverside, researchers obtained marketable yields of 7,500 to 11,100 pounds per acre with three different cultivars. Based upon the plants and their fruiting condition at the end of the harvest as well as the indeterminate nature of the crop, the potential yield was probably greater.

Use. Pick the pods at maximum length but when they are smooth, before the seeds mature or expand. At this tender stage, they can be snapped and cooked in various ways: stewed with tomato sauce; boiled and drained, then seasoned with lemon juice and oil; or simmered in butter or oil and garlic. The pale green bean is meatier and sweeter than the dark green bean, which has a less delicate taste.

Climatic requirements. This warm-season crop can be planted in a wide range of climatic conditions, but is very sensitive to cold temperatures. It can tolerate heat, low rainfall and arid soils, but the pods become short and fibrous with low soil moisture. Chinese long beans prefer high temperature, conditions under which other green beans cannot be produced.

Propagation and care. Plant seeds 1 to 2 inches deep in late spring when the soil is warm. Thin the plants to 6-12 inches in the row with 4-5 feet between rows. Since long beans are a legume some growers inoculate the seed with nitrogen fixing Rhizobium bacteria as an alternative to using nitrogen fertilizer. Use the cowpea or "EL" strain of inoculant, which is commercially available from various sources.

The plant's long, trailing growth habit requires a trellis for best production. Training the vine requires labor, about as much as for tomatoes and peas. The plant will climb by itself, but still needs some help and a very strong trellis system. The vines will grow to the top of your trellis, so don't build the trellis so high that harvesting is made difficult. Various trellising systems can be used. Chinese long beans will climb poles, especially if they are not completely vertical and the poles are 3/4 inch to 2 and a half inches in diameter, but they must be trained to the poles early in the season.

Fruits grow from open flower to marketable length in about 9 days. If the seed was not inoculated with a Rhizobium, high nitrogen fertilizer may be required when seeding and during the growing season. A field test at Riverside supplied 3 inches of water and 10 lbs of nitrogen per acre per week. Long beans require more water than cowpeas.

Aphids, particularly the black bean aphid (Aphis fabae), are drawn to the pods of this plant. By planting near other crops infested with this aphid, you are asking for trouble. Thrips tend to be a pest early in the season, but the plants will often out grow them, especially as the weather gets warmer and the plants grow faster. Mites can be a problem, primarily after insecticide applications, which often lead to mite outbreaks.

Harvest and postharvest practices. Harvested beans develop rusty patches quickly. Keep moist while in coolers, since dehydration in the coolers will lower quality and make them unmarketable. Sell beans as fresh as possible.

USDA storage recommendations are 40 to 45F (4 to 7C) at 90 to 95 percent relative humidity, with an approximate storage life of 7 to 10 days.

Seed:

Seeds Blum, Idaho City Stage, Boise, ID 83706
Sunrise Enterprises, P.O. Box 10058, Elmwood, Conn. 06110-0058
Tsang and Ma, P.O. Box 5644, Redwood City, CA 94063

More information:

Yamaguchi, Mas. World Vegetables. AVI Publishing Company, Inc. Westport, Conn. 1983. 415 pp.

Harrington, Geri. Grow Your Own Chinese Vegetables. Garden Way Publishing, Pownal, Vermont. 1984. 268 pp.

Knott, J.E. and J.A. Deanon. Vegetable Production in Southeast Asia. Univ. of Philippines, College of Agriculture, Los Banos. 1967. 366 pp.

The Packer. 1989 Produce Availability and Merchandising Guide.

Federal-State Market News Service. San Francisco Fresh Fruit and Vegetable Wholesale Market Prices 1987 and 1988. USDA and CDFA.

Tropical Products Transport Handbook. USDA Agric. Handbook 668. 1987.

Duke, James A. Handbook of Legumes of World Economic Importance. Plenum Press, N.Y., N.Y. 1981.

 

Compiled by Mark Van Horn, Student Experimental Farm, UC Davis and Claudia Myers, UC Small Farm Center.