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 caprea the height at which the graft is made. Plants can also be grown from greenwood cuttings, which make attractive creeping mounds. Hardwood cuttings are often difficult to root. Both tannin and salicin can be extracted from goat willow bark. The tree is not considered a good source of timber, as its wood is both brittle and known to crackle violently if burned. As with the closely related "Salix discolor" (American pussy willow), it is also often grown for cut flowers. See Pussy willow for further cultural information, which apply to both species. In Scandinavia it has been fairly common to