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Willow
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Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere. Most species are known as willow, but some narrow-leaved shrub species are called osier, and some broader-leaved species are called sallow (the latter name is derived from the Latin word salix, willow). Some willows (particularly arctic and alpine species), are low-growing or creeping shrubs; for example, the dwarf willow (Salix herbacea) rarely exceeds 6 cm in height, though spreading widely across the ground.
Willows are very cross fertile, and numerous hybrids occur, both naturally and in cultivation.
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Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere. Most species are known as willow, but some narrow-leaved shrub species are called osier, and some broader-leaved species are called sallow (the latter name is derived from the Latin word salix, willow). Some willows (particularly arctic and alpine species), are low-growing or creeping shrubs; for example, the dwarf willow (Salix herbacea) rarely exceeds 6 cm in height, though spreading widely across the ground.
Willows are very cross fertile, and numerous hybrids occur, both naturally and in cultivation. A well known example is the weeping willow (Salix × sepulcralis), a widely planted ornamental tree, which is a hybrid of a Chinese species, the Peking willow, and a European species, the white willow.
Description
Willows all have abundant watery sap; bark which is heavily charged with salicylic acid; soft, usually pliant, tough wood; slender branches; and large, fibrous, often stoloniferous roots. The roots are remarkable for their toughness, size, and tenacity of life, and roots readily grow from aerial parts of the plant.
The leaves are typically elongated but may also be round to oval, frequently with a serrated margin. All the buds are lateral; no absolutely terminal bud is ever formed. The buds are covered by a single scale, enclosing at its base two minute opposite buds, alternately arranged, with two, small, scale-like, fugacious, opposite leaves. The leaves are alternate, except the first pair which fall when about an inch long. They are simple, feather-veined, and typically linear-lanceolate. Usually they are serrate, rounded at base, acute or acuminate. The leaf petioles are short, the stipules often very conspicuous, looking like tiny round leaves and sometimes remaining for half the summer. On some species, however, they are small, inconspicuous, and fugacious (soon falling). In color the leaves show a great variety of greens, ranging from yellowish to bluish.
Flowers
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 staminate (male) flowers are without either calyx or corolla; they consist simply of stamens, varying in number from two to ten, accompanied by a nectariferous gland and inserted on the base of a scale which is itself borne on the rachis of a drooping raceme called a catkin, or ament. This scale is oval and entire and very hairy. The anthers are rose colored in the bud but orange or purple after the flower opens, they are two-celled and the cells open longitudinally. The filaments are threadlike, usually pale yellow, and often hairy.
The pistillate (female) flowers are also without calyx or corolla; and consist of a single ovary accompanied by a small flat nectar gland and inserted on the base of a scale which is likewise borne on the rachis of a catkin. The ovary is one-celled, the style two-lobed, and the ovules numerous.
Fruit
The fruit is a small, one-celled, two-valved, cylindrical beaked capsule containing numerous tiny (0.1 mm) seeds. The seeds are furnished with long, silky, white hairs, which allow the fruit to be widely dispersed by the wind.
Cultivation
Almost all willows take root very readily from cuttings or where broken branches lie on the ground. There are a few exceptions, including the goat willow and peachleaf willow. One famous example of such growth from cuttings involves the poet Alexander Pope, who begged a twig from a parcel tied with twigs sent from Spain to Lady Suffolk. This twig was planted and thrived, and legend has it that all of England's weeping willows are descended from this first one.
Willows are often planted on the borders of streams so that their interlacing roots may protect the bank against the action of the water. Frequently the roots are much larger than the stem which grows from them.
Ecological issues
Willows are used as food plants by the larvae of some Lepidoptera species - see list of Lepidoptera that feed on willows.
A number of willow species were widely planted in Australia, notably as erosion control measures along watercourses. They are now regarded as an invasive weed and many catchment management authorities are removing them to be replaced with native trees.
Uses
Medicine
The leaves and bark of the willow tree have been mentioned in ancient texts from Assyria, Sumer and Egypt as a remedy for aches and fever, and the Ancient 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. This is because they contain salicylic acid, the precursor to aspirin.
In 1763 its medicinal properties were observed by the Reverend Edward Stone in England. He notified the Royal Society who published his findings. 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).
Manufacturing
Willow wood is also used in the manufacture of Boxes, brooms, cricket bats (grown from certain strains of white willow), cradle boards, chairs and other furniture, dolls, flutes, poles, sweat lodges, toys, turnery, tool handles, veneer, wands and whistles.
In addition tannin, fibre, paper, rope and string, can be produced from the wood. Willows are also popular for Wicker (often from osiers), which is used in Basket weaving, fish traps, wattle fences and wattle and daub.
Agriculture
Willow bark contains auxins (plant growth hormones), especially those used for rooting new cuttings. The bark can even be used to make a simple extract that will promote cutting growth.
Apiculture
Willows produce a modest amount of nectar that bees can make honey from, and are especially valued as a source of pollen for bees.
Energy
Willow is grown for biomass or biofuel, in energy forestry systems, as a consequence of its high energy in-energy out ratio, large carbon mitigation potential and fast growth. Large scale projects to support willows development as an energy crop have been established, such as the Willow Biomass Project in the US and the Energy Coppice Project in the UK.
Willow may also be grown to produce Charcoal.
Environment
As a plant, willow is used for biofiltration, constructed wetlands, ecological wastewater treatment systems, hedges, land reclamation, landscaping, phytoremediation, streambank stabilisation (bioengineering), slope stabilisation, soil erosion control, shelterbelt & windbreak, soil building, soil reclamation, tree bog compost toilet, wildlife habitat.
Art
Willow is used as charcoal (for drawing) and in living sculptures
Religion
In religion, willow is one of the "Four Species" used in a ceremony on the Jewish holiday of Sukkot. Willow is also one of the nine sacred trees mentioned in wicca and witchcraft, with several magical uses. In the Wiccan Rede, it is described as growing by water, guiding the dead into the "Summerland", a commonly used term in Wicca to refer to the afterlife.
Willow in human culture
The willow is a famous subject in many East Asian nations' cultures, particularly in paintings (pen and ink) from China and Japan.
A Gisaeng (Korean Geisha) named Hongrang, who lived in the middle of the Joseon period, wrote the poem "By the willow in the rain in the evening", which she gave to her parting lover (Choi Gyeong-chang). Hongrang wrote: "...I will be the willow on your bedside."
Willow trees are also quite prevalent in folklore and myths. In English folklore, a willow tree is believed to be quite sinister, capable of uprooting itself and stalking travellers.
In literature
Hans Christian Andersen wrote a story called Under the Willow Tree (1853) in which children ask questions of a tree they call willow-father, paired with another entity called elder-mother.
Green Willow is a Japanese ghost story in which a young samurai falls in love with a woman called Green Willow who has a close spiritual connection with a willow tree. The Willow Wife is another, not dissimilar tale. Wisdom of the Willow Tree is an Osage Nation story in which a young man seeks answers from a Willow tree, addressing the tree in conversation as 'Grandfather'.
In JK Rowling's Harry Potter and the Chamber of Secrets, and Harry Potter and the Prisoner of Azkaban, there is an old tree on the school grounds of Hogwarts called the "Whomping Willow". It was planted in order to conceal a secret passageway that Professor Remus Lupin roamed through every full moon when he began his transformation into a werewolf.
In William Shakespeare's Hamlet, the character Ophelia climbed a willow tree when a branch broke and dropped her into the river below where she drowned. In Shakespeare's "Twelfth Night", Viola (disguised as Cesario) tells Olivia "Make me a willow-cabin at your gate/ And call upon my soul within the house." The willow here being an emblem of forsaken love. In Shakespeare's Othello, Desdemona's song before her death uses the willow imagery to highlight her lost love.
J. R. R. Tolkien's The Lord of the Rings also features a character known as Old Man Willow which traps some of Frodo's companions until they are rescued by Tom Bombadil.
In Farsi literature, the recognized adjective for 'willow' is lunatic, and lover (or lovers' heart) is compared to willow in many texts.
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See also
- Aravah, the Hebrew name of the willow, for its ritual use during the Jewish Feast of Tabernacles
- List of Lepidoptera that feed on willows
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