Willow are very cross-compatible, and numerous hybrids occur, both naturally and in cultivation. A well-known ornamental example is the weeping willow ("Salix × sepulcralis"), which is a hybrid of Peking willow ("Salix babylonica") from China and white willow ("Salix alba") from Europe. The hybrid cultivar 'Boydii' has gained the Royal Horticultural Society's Award of Garden Merit. Numerous cultivars of "Salix" L. have been developed and named over the centuries. New selections of cultivars with superior technical and ornamental characteristics have been chosen deliberately and applied to various purposes. Most recently, "Salix" has become an important source for bioenergy production and for
Salix matsudana female catkins on separate trees. The leaves are narrow, light green, around 4–10 cm long and 1–2 cm broad. The flowers are borne in catkins produced early in the spring The "Flora of China" recognizes three varieties within the species "Salix matsudana:" Many botanists, notably the Russian willow expert Alexei Konstantinovich Skvortsov, treat "Salix matsudana" as a synonym of the Peking willow "Salix babylonica", which, despite its botanical name, is also native to northern China. The only reported difference between the two is that "S. matsudana" has two nectaries in each female flower, whereas "S. babylonica" has only one; however