For other uses, see Willow (disambiguation).

The willows are deciduous trees and shrubs in the genus Salix, in 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. These plants are dioecious with male and female flowers appearing as catkins on different plants. The deciduous leaves are often elongate and serrate. The leaves of some species are eaten by the larvae of Lepidoptera such as Emperor Moth and Common Emerald.

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.

Weeping Willow

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.

Medicinal properties

Peking willow, Salix matsudana

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).

The Many Uses of Willows

Cricket bat
Cradle board
Chair & furniture
Pole, Turnery, Tool handles
Fish trap
Doll, Toy, Whistle
Charcoal
Paper
Box, Veneer
Wand, Broom
Rope
Basket weaving
Wattle fence
Wattle and daub
Streambank stabilisation (bioengineering)
Slope stabilisation
Soil erosion control
Soil building
Land reclamation
Ecological wastewater treatment system
Constructed wetland
Biofiltration
Phytoremediation
Shelterbelt & Windbreak
Agroforestry
Wildlife habitat
Living Willow Sculpture
Landscaping
Biomass energy (bioenergy)

Common Osier (Salix viminalis) leaves

External links

Salix alba

• Salix alba image from 'Flora von Deutschland Österreich und der Schweiz' (http://caliban.mpiz-koeln.mpg.de/~stueber/thome/band2/tafel_010.html)
• Salix alba at plants for a future (http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Salix+alba)

Salix purpurea

• Image of Salix purpurea from 'Flora von Deutschland Österreich und der Schweiz' (http://caliban.mpiz-koeln.mpg.de/~stueber/thome/band2/tafel_012.html)
• Salix purpurea at plants for a future (http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Salix+purpurea)