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 scouleriana Salix scouleriana Salix scouleriana (Scouler's willow; syn. "S. brachystachys" Benth., "S. capreoides" Anderss., "S. flavescens" Nutt., "S. nuttallii" Sarg., "S. stagnalis" Nutt.) is a species of willow native to western North America, from south central Alaska east to western Northwest Territory, central Manitoba, and the Black Hills of South Dakota, and south through the Rocky Mountains to Coahuila, and along the coast through British Columbia, Washington, Oregon, and the Sierra Nevada in California. Other names occasionally used include fire willow, Nuttall willow, mountain willow, and black willow. It is a deciduous shrub or small tree, depending on the environment, usually