Salix babylonica is a species of willow native to dry areas of northern China, but cultivated for millennia elsewhere in Asia, being traded along the Silk Road to southwest Asia and Europe.
Description
Salix babylonica is a medium- to large-sized deciduous tree, growing up to tall. It grows rapidly, but has a short lifespan, between 40 and 75 years. The shoots are yellowish-brown, with small buds. The leaves are alternate and spirally arranged, narrow, light green, 4–16 cm long and 0.5–2 cm broad, with finely serrate margins and long acuminate tips; they turn a gold-yellow in autumn. The flowers are arranged in catkins produced early in the spring; it is dioecious, with the male and female catkins on separate trees.
Taxonomy
Salix babylonica was described and named scientifically by Carolus Linnaeus in 1736, who knew the species as the pendulous-branched variant then recently introduced into the Clifford garden in Hartekamp in The Netherlands.
Early Chinese cultivar selections include the original weeping willow, Salix babylonica 'Pendula', in which the branches and twigs are strongly pendulous, which was presumably spread along ancient trade routes. These distinctive trees were subsequently introduced into England from Aleppo in northern Syria in 1730, and have rapidly become naturalised, growing well along rivers and in parks. These plants are all females, readily propagated vegetatively, and capable of hybridizing with various other kinds of willows, but not breeding true from seed. This type of tree is grown very easily through plant propagation. Two cultivated hybrids between pendulous Salix babylonica and other species of Salix willows also have pendulous branchlets, and are more commonly planted than S. babylonica itself:
Salix × pendulina, a hybrid with S. babylonica accepted as the female parent, but with the male parent unidentified, probably being either S. euxina or S. × fragilis, but perhaps S. pentandra. Of these possibilities, S. × fragilis is itself a hybrid, with S. alba and S. euxina as parental species.
Salix × sepulcralis, is a hybrid between S. alba and S. babylonica.
Cultivars derived from either of these hybrids are generally better adapted than S. babylonica to the more humid climates of most heavily populated regions of Europe and North America.
Relation to ''Salix matsudana''
A similar willow species also native to northern China, Salix matsudana, is now included in Salix babylonica as a synonym by many botanists, including the Russian willow expert Alexey Skvortsov. The only reported difference between the two species is S. matsudana has two nectaries in each female flower, whereas S. babylonica has only one; however, this character is variable in many willows, so even this difference may not be taxonomically significant.
Cultivation
S. babylonica, especially its pendulous-branched form, has been introduced into many other areas, including Europe and the southeastern United States, but beyond China, it has not generally been as successfully cultivated as some of its hybrid derivatives, being sensitive to late-spring frosts. In the more humid climates of much of Europe and eastern North America, it is susceptible to a canker disease, willow anthracnose, which makes infected trees very short-lived and unsightly.
Cultivars
Salix babylonica has many cultivars, including:
'Babylon' is the most widely grown cultivar of S. babylonica, with its typical weeping branches.
'Crispa' is a mutant of 'Babylon', with spirally curled leaves.
Various cultivars of Salix matsudana are now often included within Salix babylonica, treated more broadly, including:
'Tortuosa' is an upright tree with twisted and contorted branches.
Yet other weeping willow cultivars are derived from interspecific Salix hybrids, including S. babylonica in their parentage. The most widely grown weeping willow cultivar is Salix × sepulcralis 'Chrysocoma', with bright yellowish branchlets.
The epithet babylonica in this Chinese species' scientific name, as well as the related common names "Babylon willow" or "Babylon weeping willow", derive from a misunderstanding by Linnaeus that this willow was the tree described in the Bible in the opening of Psalm 137 :
Despite these Biblical references to "willows", whether in Latin or English, the trees growing in Babylon along the Euphrates River in ancient Mesopotamia and named gharab in early Hebrew, are not willows in either the modern or the classical sense, but the Euphrates poplar, with willow-like leaves on long, drooping shoots, in the related genusPopulus. Both Populus and Salix are in the plant familySalicaceae, the willow family. These Babylonian trees are correctly called poplars, not willows, in the New International Version of the Bible :
