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 brachycarpa The plant produces tiny, downy seeds which are viable for just a few days but may germinate within 12 hours of hitting a suitable substrate. There are at least two recognized varieties of this species of willow: A former subspecies, "Salix brachycarpa" subsp. "niphoclada", is now synonymous with "Salix niphoclada", another Alaskan willow species that is also commonly referred to as barren-ground willow. Of note, barren-ground willow is also the common name of a third but distinct species of willow found in Alaska, "Salix nummularia". On the Alaska North Slope, sites that supported this and other low-growing willow species before