- For other uses, see Willow (disambiguation).
The willows are deciduous trees and shrubs in the genus Salix, part of the willow family Salicaceae. There are about 350 species in this genus worldwide, found primarily on moist soils in cooler zones in the Northern Hemisphere. The leaves are deciduous, often elongate but round to oval in a few species, and with a serrated margin. Willows are dioecious with male and female flowers appearing as catkins on different plants; the catkins are produced early in the spring, often before the leaves or as the new leaves open. The fruit is a small capsule containing numerous tiny (0.1 mm) seeds embedded in white down, which assists wind dispersal of the seeds. Willows are very cross-fertile and numerous hybrids are known, both naturally occurring and in cultivation.
Some smaller species may also be known by the common names osier and sallow; the latter name is derived from the same root as the Latin salix.
The White Willow (Salix alba) is a widespread European species, which has become naturalised on many other parts of the world; it is a tree up to 30 m tall. A cultivar of it, 'Caerulea', selected for fast, straight growth, is grown in southern England, the wood being used for the manufacture of cricket bats.
The Weeping Willow, very widely planted as an ornamental tree, is also a cultivar, Salix 'Tristis', derived from a hybrid between the Chinese S. babylonica and S. alba.
Some willows, particularly arctic and alpine species, are very small; the Dwarf Willow (Salix herbacea) rarely exceeds 6 cm in height, though spreading widely across the ground.
Almost all willows take root very readily from cuttings or where broken branches lie on the ground. The most famous example of this is the poet, Alexander Pope, who begged a twig from a parcel tied with twigs sent from Spain to Lady Suffolk. This was planted and thrived and legend has it that all England's Weeping Willows are descended from this first one. There are a few exceptions to this ready growth from cuttings, including the Goat Willow and Peachleaf Willow.
Willows are used as food plants by the larvae of some Lepidoptera species including Brimstone Moth, Poplar Hawk-moth, Buff-tip, Autumnal Rustic and Small Square-spot.
Medicinal properties
The bark of the willow tree has been mentioned in ancient texts from Assyria, Sumeria and Egypt as a remedy for aches and fever, and the Greek physician Hippocrates wrote about its medicinal properties in the 5th century BC. Native Americans across the American continent relied on it as a staple of their medical treatments.
The active extract of the bark, called salicin, 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 is acidic when in a saturated solution in water (pH = 2.4), and is called salicylic acid for that reason.
In 1897 Felix Hoffmann created a synthetically altered version of salicin (in his case derived from the Spiraea plant), which caused less digestive upset than pure salicylic acid. The new drug, formally Acetylsalicylic acid, was named aspirin by Hoffmann's employer Bayer AG. This gave rise to the hugely important class of drugs known as non-steroidal anti-inflammatory drugs (NSAIDs).
Uses
External links
- Salix alba
- Salix purpurea
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Common Osier (Salix viminalis) leaves
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