Salix alba

White Willow redirects here. See White Willow (band) for the Norwegian band.

Golden Willow redirects here. See Golden Willow for information on the horse of that name.

Salix alba (White Willow) is a species of willow native to Europe and western and central Asia.^[1][2] The name derives from the white tone to the leaves.

It is a medium-sized to large deciduous tree growing up to 10-30 m tall, with a trunk up to 1 m diameter and an irregular, often leaning crown. The bark is grey-brown, 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, particularly on the underside; they are 5-10 cm long and 0.5-1.5 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 4–5 cm long, the female catkins 3–4 cm long at pollination, lenghtening as the fruit matures. When mature in mid summer, the female catkins comprise numerous small (4 mm) capsules each containing numerous minute seeds embedded in white down which aids wind dispersal.^[1][2][3]

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Ecology

  White Willows are fast-growing, but relatively short-lived, being susceptible to several diseases, including watermark disease caused by the bacterium Brenneria salicis (named because of the characteristic 'watermark' staining in the wood; syn. Erwinia salicis) and willow anthracnose, caused by the fungus Marssonina salicicola. These diseases can be a serious problem on trees grown for timber or ornament.

It readily forms natural hybrids with Crack Willow Salix fragilis, the hybrid being named Salix × rubens Schrank.^[1]

Uses

The wood is tough, strong, and light in weight, but has minimal resistance to decay. The stems (withies) from coppiced and pollarded plants are used for basket-making. Charcoal made from the wood was important for gunpowder manufacture. The bark was used in the past for tanning leather.^[1][2]

Cultivars and hybrids

A number of cultivars and hybrids have been selected for forestry and horticultural use:^[1][2]

• 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, but also for other uses where a tough, lightweight wood that does not splinter easily, is required. It is distinguished mainly by its growth form, very fast growing with a single straight stem, and also by its slightly larger leaves (10-11 cm long, 1.5-2 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.^[1]
• 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 1-2 years before turning brown. It is particularly decorative in winter; the best effect is achieved by coppicing it every 2-3 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.

• The Weeping Willow (Salix × sepulcralis 'Chrysocoma', syn. Salix 'Tristis') is a hybrid between White Willow and Peking Willow Salix babylonica.

Medicinal uses

Hippocrates wrote in the 5th century BC about a bitter powder extracted from willow bark that could ease aches and pains and reduce fevers.^{[citation needed]} This remedy is also mentioned in texts from ancient Egypt, Sumer, and Assyria.^{[citation needed]} The Reverend Edmund Stone, a vicar from Chipping Norton in Oxfordshire England, noted in 1763 that willow bark was effective in reducing a fever.^[4]

The active extract of the bark, called salicin, after the Latin name Salix, was isolated to its crystalline form in 1828 by Henri Leroux, a French pharmacist, and Raffaele Piria, an Italian chemist, who then succeeded in separating out the acid in its pure state. Salicin, like aspirin, is a chemical derivative of salicylic acid.

References

Photographs and illustration