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Willow

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Willows
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Willow.jpg
Weeping Willow


Weeping Willow
Scientific classification
Kingdom:Plantae
Division:Magnoliophyta
Class:Magnoliopsida
Order:Malpighiales
Family:Salicaceae
Genus:Salix
Species

About 350, including:
Salix acutifolia - Violet Willow
Salix alaxensis - Alaska Willow
Salix alba - White Willow
Salix alpina - Alpine Willow
Salix amygdaloides - Peachleaf Willow
Salix arbuscula - Mountain Willow
Salix arbusculoides - Littletree Willow
Salix arctica - Arctic Willow
Salix atrocinerea
Salix aurita - Eared Willow
Salix babylonica - Peking Willow
Salix barrattiana - Barratt's Willow
Salix bebbiana - Beaked Willow
Salix boothii - Booth Willow
Salix bouffordii
Salix brachycarpa - Barren-ground Willow
Salix cacuminis
Salix candida - Sage Willow
Salix caprea - Goat Willow
Salix caroliniana - Coastal Plain Willow
Salix chilensis
Salix cinerea - Grey Sallow
Salix cordata
Salix daphnoides
Salix discolor - Pussy Willow
Salix fragilis - Crack Willow
Salix eastwoodiae - Eastwood's Willow
Salix eleagnos
Salix eriocephala - Diamond Willow
Salix exigua - Sandbar Willow
Salix foetida
Salix geyeriana
Salix glauca
Salix hainanica - Hainan Willow
Salix helvetica - Swiss Willow
Salix herbacea - Dwarf Willow
Salix humboldtiana - Chile Willow
Salix humilis - Upland Willow
Salix interior
Salix kusanoi
Salix lanata - Woolly Willow
Salix lapponum - Downy Willow
Salix lasiandra - Pacific Willow
Salix lasiolepsis - Arroyo Willow
Salix lucida - Shining Willow
Salix matsudana - Chinese Willow
Salix mucronata
Salix myrsinifolia - Dark-leaved Willow
Salix myrsinites - Whortle-leaved Willow
Salix nigra - Black Willow
Salix pedicellaris - Bog Willow
Salix pentandra - Bay Willow
Salix petiolaris - Slender Willow
Salix phylicifolia - Tea-leaved Willow
Salix planifolia
Salix polaris - Polar Willow
Salix pseudo-argentea
Salix purpurea - Purple Willow
Salix pyrifolia - Balsam Willow
Salix repens - Creeping Willow
Salix reticulata - Net-leaved Willow
Salix retusa
Salix rosmarinifolia - Rosemary-leaved Willow
Salix salicicola
Salix scouleriana - Scouler's Willow
Salix sericea - Silky Willow
Salix serissima - Autumn Willow
Salix sitchensis
Salix tetrasperma
Salix thorelii
Salix triandra - Almond Willow
Salix viminalis - Common Osier
Salix waldsteiniana

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, though there are a few exceptions, 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, 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

Template:Commonsda:Pil (Salix) de:Weiden (Botanik) it:Salice ja:ヤナギ nl:Wilg fi:Paju pl:Wierzba

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