Green beans are another name for soybeans and peas. Soybean belongs to leguminous annual climbing herbs. According to the color of its cotyledons, it can be divided into two types: green-skinned and green-kernel soybeans and green-skinned Ren Huang soybeans. It is one of the important food crops in China with a cultivation history of 5000 years. Widely planted in China, produced in Northeast China, North China, Shaanxi, Sichuan and the lower reaches of the Yangtze River.

I. Morphological characteristics

Green beans are soybeans with turquoise seed coats. According to the color of its cotyledons, it can be divided into two types: green-skinned and green-kernel soybeans and green-skinned Ren Huang soybeans. Stems stout, densely covered with long gray bristles. Petiole long, densely gray long bristles; Stipules are small and lanceolate; Tripartite compound leaves, terminal lobules rhomboid-ovate, 7-13cm long and 2-6cm wide, with an acuminate apex, a wide wedge-shaped or round base, white villous on both sides, and small lateral lobules obliquely ovate; Leaf rachis and petiole are densely covered with yellow long bristles.

Racemes axillary, bracts and bracteoles lanceolate and hairy; Calyx-shaped, calyx teeth 5, lanceolate, the longest teeth below 1, all densely white villous; Corolla small, white or lavender, slightly longer than calyx; The apex of the flag flap is slightly concave, the wing flap has 2 ears, and the keel flap is sickle-shaped; Stamens 10, dimorphic; Ovary linear and hairy. Pods are oblong, slightly curved, drooping, yellow-green, with dense green bristles and edible seeds.

Second, the distribution area

According to China's climate zoning, except for high altitude and high latitude areas with insufficient heat and areas with annual precipitation below 250 mm and no irrigation conditions; It is usually a kind of green beans. China green beans are mainly concentrated in Northeast Plain, Huanghuai Plain, Yangtze River Delta and Jianghan Plain.