Salix alba (white willow) is a species of willow native to Europe and western and central Asia. The name derives from the white tone to the undersides of the leaves. It is a medium-sized to large deciduous tree growing up to 10Ц30 m tall, with a trunk up to 1 m diameter and an irregular, often-leaning crown. The bark is grey-brown, and deeply fissured in older trees. The shoots in the typical species are grey-brown to green-brown. The leaves are paler than most other willows, due to a covering of very fine, silky white hairs, in particular on the underside; they are 5Ц10 cm long and 0.5Ц1.5 cm wide. The flowers are produced in catkins in early spring, and pollinated by insects. It is dioecious, with male and female catkins on separate trees; the male catkins are 4Ц5 cm long, the female catkins 3Ц4 cm long at pollination, lengthening as the fruit matures. When mature in midsummer, the female catkins comprise numerous small (4 mm) capsules, each containing numerous minute seeds embedded in white down, which aids wind dispersal. A number of cultivars and hybrids have been selected for forestry and horticultural use: Salix alba 'Caerulea' (cricket-bat willow; syn. Salix alba var. caerulea (Sm.) Sm.; Salix caerulea Sm.) is grown as a specialist timber crop in Britain, mainly for the production of cricket bats, and for other uses where a tough, lightweight wood that does not splinter easily is required. It is distinguished mai ly by its growth form, very fast-growing with a single straight stem, and also by its slightly larger leaves (10Ц11 cm long, 1.5Ц2 cm wide) with a more blue-green colour. Its origin is unknown; it may be a hybrid between white willow and crack willow, but this is not confirmed. Salix alba 'Vitellina' (golden willow; syn. Salix alba var. vitellina (L.) Stokes) is a cultivar grown in gardens for its shoots, which are golden-yellow for one to two years before turning brown. It is particularly decorative in winter; the best effect is achieved by coppicing it every two to three years to stimulate the production of longer young shoots with better colour. Other similar cultivars include 'Britzensis', 'Cardinal', and 'Chermesina', selected for even brighter orange-red shoots. Salix alba 'Sericea' (silver willow) is a cultivar where the white hairs on the leaves are particularly dense, giving it more strongly silvery-white foliage. Salix alba 'Vitellina-Tristis' (golden weeping willow, synonym 'Tristis') is a weeping cultivar with yellow branches that become reddish-orange in winter. It is now rare in cultivation and has been largely replaced by Salix sepulchralis group 'Chrysocoma'. It is, however, still the best choice in very cold parts of the world, such as Canada, the northern US, and Russia. The golden hybrid weeping willow (Salix sepulchralis group 'Chrysocoma') is a hybrid between white willow and Peking willow Salix babylonica.