Salix the genus, Willow the genus
Salix L. (1753), the willow, in the family Salicaceae, contains at least 300 species, mainly in the northern hemisphere.

Description Trees to 30m, or shrubs; in the arctic S. herbacea L. less than 1cm above ground. The leaves are alternate or, rarely, opposite, deciduous, usually lanceolate to ovate, undivided, to 20cm long in the Chinese S. magnifica Hemsl.. The flowers are in upright, catkin-like heads, unisexual, with males and females on different trees, usually opening in spring. The male flowers have a thin, often silky scale, 1 or more nectary scales, and usually 2 but up to 12 stamens, sometimes with fused filaments. Female flowers have a silky scale, nectar-secreting glands, and a 1-celled ovary with 2–4 stigmas. Pollination is by insects, particularly bees and moths, only rarely by wind. The fruits are small, flask-shaped capsules, splitting into 2, with small seeds attached around the lower part; each seed is surrounded by silky hairs to aid dispersal by wind.

Key Recognition Features The alternate leaves and 1-scaled winter buds. The upright male or female catkins are easy to recognise when the plants are in flower.

Evolution and Relationships The family Salicaceae is superficially similar to the catkin-bearing trees such as hazel (Corylus), but is now considered an isolated family, closer to the Flacourtiaceae in the order Violales, with which it shares some rust fungi. Of the 2 main genera, Salix are insect-pollinated while Populus are wind-pollinated. Two rarer and very closely related genera are found in Japan: Toisusu Kimura, syn. Salix urbaniana Seemen, has pendulous, willow-like catkins and is insect-pollinated; Chosenia Nakai, syn. Salix arbutifolia Pallas, is a large tree also found in Korea and eastern Siberia and has willow-like leaves but reddish, hanging male catkins, and is wind-pollinated. Hybrids between these 2 genera are found where they grow together.


Ecology and Geography Usually found in wet places by streams or rivers, as the seeds are very short-lived and shed in summer. Found throughout the temperate parts of the northern hemisphere; rare in South America and Africa, and absent as a native genus from Australia and New Zealand.

Comment Many species are grown for ornament, especially those with furry catkins on bare twigs in the spring, known as pussy willow, or palm, as they are often open on Palm Sunday. The weeping willows, S. x sepulcralis Simonkai, S. pendulina Wend., and the Chinese S. babylonica L., are planted for their gracefully hanging branches. Some species are grown for timber, notably S. alba L. subsp. caerulea (Smith) Smith, used for cricket bats. Many species, especially the osier, S. viminalis L., are planted for basket-making. Other fast-growing species and hybrids are now planted for biomass. Sallows, S. capraea L. and S. cinerea L., are used as a source of charcoal, both for drawing and for making gunpowder. Aspirin, acetylsalicylic acid, was originally extracted from willow bark, where it is in the form of salicine, an alkaloid similar to quinine. In the past the leaves were sometimes used as tea, and the bark dried for winter and mixed with oatmeal in times of famine.