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 lasiolepis forest, red fir forest, lodgepole pine forest, and grasslands. Arroyo Willow (Salix lasiolepis) is a severe allergen. Occurs in following seasons depending on latitude and elevation: Spring. "Salix lasiolepis" is a deciduous large shrub or small multi−trunked tree growing to tall. The shoots are yellowish brown and densely hairy when young. The leaves are 3.5–12.5 cm long and broadly lanceolate in shape. They are green above and glaucous green below. The undersides are covered with whitish or rusty hairs which gradually wear off during the summer. The flowers are arranged in yellow catkins 1.5–7 cm long which are produced in