Willow

• 1. Introduction

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  The willow tree has a famous origin story in England, and it begins with a parcel of twigs. A shipment sent from Spain to Lady Suffolk arrived tied up with willow twigs. The poet Alexander Pope begged one of them for himself. He planted it, and it thrived. Legend has it that every weeping willow in England descends from that single twig. True or not, the tale shows how readily this tree takes hold wherever a piece of it meets damp ground. The willow, genus Salix, is far older and far stranger than a garden ornament. Why do so many people believe it gave the world aspirin? How did one tree end up in fishing nets, cricket bats and the framework of boats? And why do traditions in China, Japan and England treat it as a place where spirits gather?

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• 2. Names and Kin

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  Around 350 species of Salix are recognised, plus numerous hybrids, and most of them simply go by the name willow. Narrow-leaved shrubs are often called osiers instead. Broader-leaved species are called sallows, a word from Old English sealh that is related to the Latin salix. The group stretches from towering trees to the dwarf willow, Salix herbacea, which rarely exceeds 6 cm in height yet spreads widely across the ground.

  In 1753, the botanist Carl Linnaeus gave the genus its scientific name. The Romans had already used salix for various willows. One theory traces the word to a Celtic language, where sal means near and lis means water, a nod to the tree's habitat. The species that anchors the genus name is Salix alba, the white willow.

  Botanists still disagree about how to divide the family. Studies of form usually recognise three or five subgenera, with Salix, Chamaetia and Vetrix as the core. Some researchers split off Longifoliae and Protitae from the first. Studies of ancestry suggest that Chamaetia and Vetrix belong together in one clade. The oldest fossils of the genus come from the early Eocene of North America. Europe's earliest appear in the Early Oligocene.

  Willows cross with one another so freely that over 160 hybrids have been named. The best known is the weeping willow, Salix × sepulcralis. It comes from the Peking willow, Salix babylonica, of China and the white willow of Europe. The widely planted Chinese willow Salix matsudana is now treated as the same species as Salix babylonica. Many cultivars have earned the Royal Horticultural Society's Award of Garden Merit. Their names were compiled until 2021 by a United Nations food and agriculture working party, which is no longer active.

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• 3. Spring Clock

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  In the northern hemisphere, a willow can leaf out as early as February. The trigger is air temperature. If daytime highs reach 10 degrees Celsius for a few days in a row, the tree tries to put out leaves and flowers. Willows are among the earliest woody plants to open in spring and among the last to let go in autumn.

  The shortening of daylight to roughly ten hours and 25 minutes triggers leaf drop. That moment shifts with latitude. Boreal species such as Salix alaxensis can shed leaves in the first week of October. Willows in far southern areas hold on until the third week of December.

  The leaves themselves vary in shape and shade. Most are elongated and serrated, though some are round to oval, and their greens range from yellowish to bluish. The stipules at the leaf base can look like tiny round leaves and sometimes last half the summer. Semi-evergreen willows are rare, with Salix micans and Salix australior of the eastern Mediterranean as examples. Every bud is lateral, and no true terminal bud ever forms.

  Salix martiana is the single exception to the willow rule of separate sexes. Every other willow is dioecious, with male and female catkins on different plants. They appear early in spring, often before the leaves. Male flowers carry two to 10 stamens, and their anthers are rose-colored in the bud before turning orange or purple. Female flowers hold a single ovary with a two-lobed style. Neither sex has petals or a calyx.

  The seeds are tiny, plentiful and carried by wind and water, yet they stay viable only for a few days. They need warm, moist conditions to root. Stumps and fallen branches can also regrow, and almost all willows root readily from cuttings. The peachleaf willow, Salix amygdaloides, is the exception. Underground, the roots are large, fibrous and remarkably tenacious, and they sprout readily from aerial parts of the plant. The bark sap is rich in a compound called salicin.

  Willows tolerate shade but tend to be short-lived. They need some disturbance to outcompete conifers and large deciduous trees.

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• 4. Life Around Willows

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  Some Native Americans met the willow's need for disturbance with fire. They allowed wildfires to burn, and sometimes set fires on purpose, so that new stands could form.

  Bees have reason to be grateful. Willows give a modest amount of nectar, from which bees can make honey, and they are especially prized as a source of early pollen. Beavers use willows to build dams. The larvae of some Lepidoptera, such as the mourning cloak butterfly, feed on the foliage. Other animals browse the leaves or shelter among the branches.

  More than a hundred aphid species, including members of Chaitophorus, live on willows. They form large colonies on the underside of leaves and feed on plant juices. Ants, such as wood ants, climb the trees to collect aphid honeydew, and wasps sometimes do the same. In North America, the willow lace bug, Corythucha elegans, belongs to the family Tingidae. The gall Rhabdophaga rosaria also appears on willows. Rust fungi of the genus Melampsora cover the leaves with orange spots.

  In Australia, a small number of willow species were widely planted as erosion control along watercourses. They are now regarded as invasive weeds across southern Australia. They carry the label Weeds of National Significance. Many catchment management authorities are removing them and replacing them with native trees.

  Closer to home, willow roots hunt aggressively for moisture. In residential areas, they have a reputation for clogging French drains, weeping tiles, septic systems, storm drains and sewers, especially older pipes of tile, concrete or ceramic. Newer PVC sewer pipes leak much less at the joints, so they suffer far less.

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• 5. Ancient Remedies

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  Some 5,000 medical prescriptions have been identified from Babylonian writings of the 7th to 3rd centuries BC. They involve 1,300 drugs from 340 different plants. Whether any of them name willow is uncertain, because reading cuneiform for one specific plant treating one recognisable illness is hard. The Sumerian narrative Gilgameš, Enkidu and the Nether World recommends the seeds of the Haluppu-tree for infertility. That tree could have been oak, poplar or willow.

  Texts from Assyria, Sumer and Egypt mention willow leaves and bark. In the fifth century BC, the Greek physician Hippocrates wrote about their properties as a folk medicine. The Egyptian Ebers Papyrus mentions willow of uncertain species in three remedies. One is a poultice to "make the met supple," with 36 other ingredients, among them the fruit of the dompalm, beans and amaa grains. Another treats the "Great Debility" with "rush from the green willow tree" combined with ass's semen, fresh bread, herbs of the field, figs, grapes and wine. A third uses willow as a stiffening agent in a mixture of fat flesh, figs, dates, incense, garlic and sweet beer, meant to put the heart in working order.

  The Roman author Aulus Cornelius Celsus mentions willow only once. He prescribed leaves, pounded and boiled in vinegar, for uterine prolapse. Pain relief was unlikely to be his aim, since the next paragraph recommends cauterization.

  Nicholas Culpeper, in The Complete Herbal, offered many uses. They included staunching wounds, stopping urine that had stalled, and to "stay the heat of lust." He also advised mixing burnt willow bark ash with vinegar to remove warts and corns, which resembles modern uses of salicylic acid. He never mentions pain relief. William Turner, writing about 1597, recommended leaves and bark boiled in wine to "stay the spitting of blood." For fevers, he suggested setting green boughs around the beds of the sick, since they would "mightily cool the heat of the air."

  In 1763, the Reverend Edward Stone of Chipping Norton, Oxfordshire, wrote to the Royal Society about powdered white willow bark. He had noticed that it tasted bitter, like the "Peruvian Bark" (cinchona) used against fevers. Over several years he tested it on as many as fifty patients and found it highly effective, especially when mixed with cinchona. Whether the effect was real is unknown. Others experimented with his remedy, but medical practitioners never adopted it. During the American Civil War, Confederate forces also tried willow against malaria, without success.

  Jules Verne captured this uncertainty in his 1875 novel The Mysterious Island. A character named Herbert Brown suffers a fever after a bullet wound, and Verne notes that willow bark had been "justly considered" a substitute for Peruvian bark. In the story, powdered willow bark does nothing, and quinine finally saves him.

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• 6. Road to Aspirin

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  In 1876, the Scottish physician Thomas MacLagan gave salicin to patients with acute rheumatism, with considerable success. He reported the results in The Lancet. German scientists meanwhile tried salicylic acid as sodium salicylate, with less success and more severe side effects. Treating rheumatic fever with salicin slowly won some acceptance among doctors.

  The 1880s brought the discovery of acetanilide, which set off an acetylation craze among chemists. They experimented with adding an acetyl group to many aromatic organic compounds. Yet the chemist Charles Frédéric Gerhardt had already made acetylsalicylic acid in 1853, by treating sodium salicylate with acetyl chloride. In 1897, more than 40 years later, Felix Hoffmann created the same acid, this time derived from the Spiraea plant. It was found in 1899 to relieve pain. His employer, Bayer AG, named it Aspirin. The link between aspirin and willow is therefore only indirect.

  That has not stopped the belief that willow was the ancient painkiller. In the late 1990s, Daniel Moerman reported many Native American uses of willow. One modern field guide goes further, claiming that "Several references mention chewing willow bark as an analgesic for headache and other pain, apparently presaging the development of aspirin in the late 1800s."

  The record of herbalists tells a different story. In the early 20th century, Maud Grieve recommended the bark and powdered root of white willow as a tonic and astringent. She used it for dyspepsia, worms, chronic diarrhoea and dysentery. She never mentions pain relief, even though aspirin was widely known by then. She believed tannin was the active ingredient.

  The painkiller idea arrived long after aspirin did, and it may rest on a belief that willow actually contains aspirin. Academic journals, among them the British Journal of Haematology, have published articles asserting that the ancients used willow for pain. Many papers, books and products now repeat the claim.

  In truth, willow bark has low levels of salicin and works differently from aspirin. It offers milder but broader anti-inflammatory effects without damaging the stomach, though it is unsuitable for people with aspirin allergies. The Committee on Herbal Medicinal Products in the European Union has concluded that dry extracts can treat lower back pain in the short term. Applied to skin, willow compounds have been reported to improve vascularity, photo-aging and wound healing. An extract has also been used against Malassezia fungus on the scalp to treat dandruff.

  In the European Union and the United Kingdom, a water extract of willow bark is even approved as a basic substance against scab, leaf peach curl and powdery mildew on grapes, apples and peaches.

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• 7. Woven and Worked

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  A fishing net made from willow dates back to 8300 BC, which may make it one of humanity's earliest manufactured items. Later, rod-like willow shoots called osiers or withies, often grown in pollards, were woven into baskets, fish traps and wattle fences. They also formed the wattle in wattle and daub house walls. One form of the Welsh coracle boat traditionally uses willow in its framework.

  Thin or split rods can be woven into wicker. Willow bends around sharp corners in basketry and is less likely to split than many other woods. Its wood also goes into boxes, brooms, cricket bats, cradle boards, furniture, dolls, willow flutes, tool handles, toys, wands and whistles. Tannin, fibre, paper, rope and string can be produced from it. Double basses use willow for backs, sides and linings, and bass repairers use it for splines and blocks.

  The Quinault people of Washington made willow bark into a twine that sometimes served as harpoon line. Other Native American tribes used the wood to start fires by friction and the shoots to weave baskets. Branches and stems went into fishing weirs and other structures.

  During World War II, the British made parachute baskets from willow. Light and strong, they could be shaped as needed and bounced on impact. Production reached about 2000 tonnes a year across some 630 manufacturers, employing 7000 basket makers. Lawrence Ogilvie, a plant pathologist, worked at Long Ashton Research Station near Bristol on these willows and their diseases. He had studied willow diseases for a Cambridge University master's thesis in the 1920s.

  In Tokyo, the high-end shopping district of Ginza has a long history of cultivating willow and is known for its willow-lined streets. Willow is used to dye textiles for kimono. The kimono retailer Ginza Motoji hosts annual dyeing lessons with fifth grade students of Taimei Elementary School.

  Artists use willow for drawing charcoal and for living sculptures, woven from live rods into domes and tunnels. Gardeners make decorative panels and obelisks from its stems. Researchers have explored fast-growing willows for biomass and biofuel, through the Willow Biomass Project in the US and the Energy Coppice Project in the UK. Willows are planted along stream borders so that interlacing roots protect the bank from water. Research into using willows to filter wastewater has not proved commercially viable.

  Poor people at one time ate willow catkins cooked into a mash. The inner bark, young leaves and underground shoots can also be eaten.

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• 8. Sacred and Haunted

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  Leviticus 23:40 lists the willow among four species associated with the Jewish festival of Sukkot. Willow branches are used in the synagogue service on Hoshana Rabbah, the seventh day of the festival. Orthodox churches use willow branches in place of palms on Palm Sunday. In Buddhism, a willow branch is one of the chief attributes of Guanyin, the bodhisattva of compassion. Traditional pictures often show her seated on a rock, with a willow branch in a vase of water beside her.

  On the Chinese Qingming Festival, some people carry willow branches while sweeping tombs. They also hang branches on gates and front doors. Legend says the ruler of the underworld lets the spirits of the dead return to earth that day, and willow is believed to keep unwelcome visitors away. In Taoist practice, a small willow carving is used to reach the dead. The image is sent to the underworld, where the spirit is said to enter it and return with the information that surviving relatives want.

  In Korea, during the middle of the Joseon Dynasty, a gisaeng named Hongrang wrote a poem called "By the willow in the rain in the evening." She gave it to her parting lover, Choi Gyeong-chang. In it she wrote, "I will be the willow on your bedside." The willow is also a favourite subject in the pen and ink paintings of China and Japan.

  Japanese tradition links the willow with ghosts, and people say a ghost will appear where one grows. In the ghost story "Green Willow," a young samurai falls in love with a woman of that name, who has a close spiritual bond with a willow tree. "The Willow Wife" is a similar tale. English folklore is darker still, holding that a willow can uproot itself and stalk travellers.

  Other stories treat the tree as a source of wisdom. In the Osage Nation story "Wisdom of the Willow Tree," a young man seeks answers from a willow and addresses it as Grandfather. In his 1853 tale "Under the Willow Tree," Hans Christian Andersen has children put questions to a tree they call willow-father, paired with a being named elder-mother.

  Rome's Viminal Hill, one of its Seven Hills, still carries the Latin word for osier, viminia, in its name.

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