Salix cupularis is a small shrub from the genus of the willow (Salix) with 1.5 to 2.7 centimeters long leaf blades. The natural range of the species is in China.
Salix cupularis is a small shrub. The branches are initially reddish-brown or black-purple and later gray and have clearly developed nodes. The buds are brown-red, shiny, narrowly elongated, and about 4 millimeters long. The leaves have roundish, about 5 millimeters long stipules. The petiole is yellowish, and about a third to a half times as long as the leaf blade. The leaf blade is elliptical or obovate-elliptical, rarely rounded, 1.5 to 2.7 centimeters long and 1 to 1.5 centimeters wide, entire, with a rounded or broad wedge-shaped base and a more or less rounded and acuminate or long pointed end. The upper side of the leaf is dull green and bare, the underside greenish. Six to nine pairs of side veins are formed.
As male inflorescences, about 2 centimeters long are catkins formed. The peduncle is short and has three leaflets. The bracts are obovate, about half as long as the stamens, hairy down or hairless on the underside of the leaf towards the tip. They have a rounded tip. Male flowers have adaxially and abaxially narrowly ovate-petiolate nectar glands connected at the base. There will be two stamenseducated. The stamens are hairy down at the base. Female catkins are elliptical to short cylindrical, about 1 centimeter long, and petiolate. The bracts are ovate to broadly ovate, 1.5 to 2 millimeters long and have a rounded tip. Female flowers have an adaxial and a somewhat smaller abaxial nectar gland. The adaxial gland is divided into two or three parts, the base of the gland is fused and thus resembles a disc. The ovary is long ovate, hairless, and short stalks. The stylus is about 1 millimeter long, the stigma has two columns. The capsule fruits are about 3 millimeters long when ripe. Salix cupularis flowers in June with the leaf shoots or a little later, the fruits ripen in July and August.
The natural range is in the northwest of the Chinese provinces of Gansu, Qinghai, Shaanxi, Sichuan, and in Inner Mongolia. Salix cupularis grows on mountain slopes at elevations of 2500 to 4000 meters.
Salix cupularis is a kind from the kind of willow (Salix), in the family of the pasture plants (Salicaceae). There, it is the section Sclerophyllae assigned. It was described scientifically for the first time in 1923 by Alfred Rehder in Arnoldia, the Journal of the Arnold Arboretum. No synonyms are known. The genus name Salix is Latin and has been from the Romans used for different types of willow.
There are two varieties: