Taxus baccata is a species of coniferous tree in the family Taxaceae. It is the tree originally known as yew, though to distinguish it from related species it is sometimes called common yew, European yew, or, in North America, English yew. It is a woodland tree in its native range, which spans much of Europe and parts of West Asia, the Caucasus and Northwest Africa. All parts of the plant except the fleshy aril are poisonous, with toxins that can be absorbed through inhalation, ingestion, and transpiration through the skin.
The wood has been prized for making longbows and for musical instruments such as lutes. Yews are often grown as ornamental trees, hedges or topiaries, including in churchyards, where they sometimes reach great age; many explanations have been given for this planting, especially that the yew is associated with death, immortality, and rebirth. Some place names derive from the Proto-Celtic *eburos, but scholars disagree as to whether this meant the yew tree.
Taxonomy
The species Taxus baccata was first described in 1753 by Carl Linnaeus in his Species Plantarum. The name remains accepted, despite the many descriptions by later taxonomists, resulting in 108 synonyms. Linnaeus created the generic name Taxus, perhaps from the Greek toxon, a bow.
The word yew is from Old English , , ultimately from Proto-Indo-European *h₁eyHw-, via Proto-Germanic *iwo, which also gave rise to Celtic forms such as Old Irish ēo, Welsh . It became Old English , and Middle English . Baccata is Latin for 'bearing berries'.
Description
Yews are small to medium-sized trees, growing up to or exceptionally tall, with a trunk up to or exceptionally in diameter. The bark is thin, scaly reddish-brown, and comes off in small flakes aligned with the stem. The leaves are flat, dark green, long, broad, and arranged spirally on the stem, but with the leaf bases twisted to align the leaves in two flat rows on either side of the stem, except on erect leading shoots where the spiral arrangement is more obvious.
The seed cones are modified, each cone containing a single seed, which is long and almost surrounded by a fleshy scale which develops into a soft, bright red berry-like aril. The aril is long and wide and open at the end. The arils mature 6 to 9 months after pollination.
The aril is gelatinous and very sweet tasting. The male cones are globose, in diameter, and shed their pollen in early spring. Yews are mostly dioecious with male and female cones on separate trees, but occasional individuals can be variably monoecious, or change sex with time.
Distribution
The yew is native to all countries of Europe (except Iceland), the Caucasus, and beyond from Turkey eastwards to northern Iran. Its range extends south to Morocco and Algeria in North Africa, and parts of Southwest and South Asia. A few populations are present in the archipelagos of the Azores and Madeira. The limit of its northern Scandinavian distribution is its sensitivity to frost, with global warming predicted to allow its spread inland. It has been introduced elsewhere, including the United States.
Habitat and ecology
The yew's richest central European populations are in Swiss yew-beech woodlands, on cool, steep marl slopes up to in elevation in the Jura Mountains and Alpine foothills. In the UK it grows best on steep slopes of the chalk downs, forming extensive stands invading the grassland outside the beech woods. In more continental climates of Europe it fares better in mixed forests of both coniferous and mixed broadleaf-conifer composition. Under its evergreen shade, no other plants can grow.
The species prefers steep rocky calcareous slopes. It rarely develops beyond saplings on acid soil when under a forest canopy, but is tolerant of soil pH when planted by humans, such as their traditional placement in churchyards and cemeteries, where some of the largest and oldest trees in northwestern Europe are found. It grows well in well-drained soils, tolerating nearly any soil type, typically humus and base-rich soils, but also on rendzina and sand soils given adequate moisture. They can survive temporary flooding and moderate droughts. Roots can penetrate extremely compressed soils, such as on rocky terrain and vertical cliff faces. It normally appears individually or in small groups within the understory, but forms stands throughout its range, such as in sheltered calcareous sites. It is extremely shade-tolerant, with the widest temperature range for photosynthesis among European trees, able to photosynthesize in winter after deciduous trees have shed their leaves. It can grow under partial canopies of beech and other deciduous broad-leafed trees, though it only grows into large trees without such shade.
The arils are eaten by birds, which disperse the hard seeds undamaged in their droppings. Although they contain toxins, the kernels are extracted and eaten by some birds, such as hawfinches, greenfinches, and great tits.
Conservation
Historically, yew populations were gravely threatened by felling for longbows and destruction to protect livestock from poisoning. It is now endangered in parts of its range due to intensive land use. The species is also harvested to meet pharmaceutical demand for taxanes. Trees are often damaged by browsing and bark stripping. Yew's thin bark makes it vulnerable to fire. Its toxicity protects against many insects, but the yew mite causes significant bud mortality, and seedlings can be killed by fungi.
Clippings from ancient specimens in the United Kingdom, including the Fortingall Yew, were taken to the Royal Botanic Gardens in Edinburgh to form a mile-long hedge. The purpose of this "Yew Conservation Hedge Project" is to maintain the DNA of Taxus baccata. A conservation programme was run in Catalonia in the early 2010s by the Forest Sciences Centre of Catalonia in order to protect genetically endemic yew populations and preserve them from overgrazing and forest fires. In the framework of this programme, the 4th International Yew Conference was organised in the Poblet Monastery in 2014. There has been a conservation programme in northern Portugal and Northern Spain (Cantabrian Range).
Harmfulness
Toxicity
The entire plant is poisonous, with the exception of the aril (the red flesh of the "berry" covering the seed). Yews contain numerous toxic compounds, including alkaloids, ephedrine, nitriles, and essential oil. The most important toxins are taxine alkaloids; these are cardiotoxic compounds which act via calcium and sodium channel antagonism. If any leaves or seeds of the plant are ingested, urgent medical attention is recommended as well as observation for at least six hours after the point of ingestion.
Yew poisonings are relatively common in both domestic and wild animals which consume the plant accidentally, resulting in numerous livestock fatalities. Taxines are absorbed efficiently via the skin. Rabbits and deer have a level of immunity to the poisonous alkaloids.
According to Ondřej Piskač, "The lethal dose for an adult is reported to be 50 g of yew needles. Patients who ingest a lethal dose frequently die due to cardiogenic shock, in spite of resuscitation efforts." There are currently no known antidotes for yew poisoning, but drugs such as atropine have been used to treat the symptoms. Taxine remains in the plant all year, with maximal concentrations appearing during the winter. Dried yew plant material retains its toxicity for several months, and even increases its toxicity as the water is removed. Fallen leaves should therefore also be considered toxic. Poisoning usually occurs when leaves of yew trees are eaten, but in at least one case, a victim inhaled sawdust from a yew tree.
Allergenicity
Male yews are extremely allergenic, blooming and releasing abundant amounts of pollen in the spring, with an OPALS allergy scale rating of 10 out of 10. Completely female yews have an OPALS rating of 1, the lowest possible, trapping pollen while producing none. While yew pollen does not contain sufficient taxine alkaloids to cause poisoning, its allergenic potential has been implicated in adverse reactions to paclitaxel treatment.
Uses
Yew wood was historically important, finding use in the Middle Ages in items such as musical instruments, furniture, and longbows. The species was felled nearly to extinction in much of Europe. In the modern day, it is not considered a commercial crop due to its very slow growth, but it is valued for hedging and topiary. Certain compounds in yew clippings are precursors of the chemotherapy drug taxol.National Non-Food Crops Centre, "Yew" . Retrieved on 2009-04-23.
Woodworking
Wood from the yew is a closed-pore softwood, similar to cedar and pine. Easy to work, it is among the hardest of the softwoods, yet it possesses a remarkable elasticity, making it ideal for products that require springiness, such as bows. The wood is esteemed for cabinetry and tool handles. The hard, slow-growing wood also finds use in gates, furniture, parquet floors, and paneling. Its typical burls and contorted growth, with intricate multicolored patterns, make it attractive for carving and woodturning, but also make the wood unsuited for construction. It is good firewood and is sometimes burnt as incense. Due to all parts of the yew and its volatile oils being poisonous and cardiotoxic, a mask should be worn if one comes in contact with sawdust from the wood.
One of the world's oldest surviving wooden artifacts is a Clactonian yew spear head, found in 1911 at Clacton-on-Sea, in Essex, England. Known as the Clacton Spear, it is around 400,000 years old. Another spear made from yew is the Lehringen spear found in Germany, dating to around 120,000 years ago, thought to have been created by Neanderthals, and near the skeleton of a straight-tusked elephant which it was likely used to kill.Milks, A. (2020) Yew wood, would you? An exploration of the selection of wood for Pleistocene spears. In: Berihuete-Azorin, M., Martin Seijo, M., Lopez-Bulto, O. and Pique, R. (eds.) The Missing Woodland Resources: Archaeobotanical studies of the use of plant raw materials. Advances in Archaeobotany, 6 (6). Barkhuis Publishing, Groningen, pp. 5-22.
Longbows
The trade of yew wood to England for longbows was so robust that it depleted the stocks of good-quality, mature yew over a vast area. The first documented import of yew bowstaves to England was in 1294. In 1423, the Polish king commanded protection of yews in order to cut exports, facing nearly complete destruction of local yew stock. In 1470, compulsory archery practice was renewed, and hazel, ash, and laburnum were specifically allowed for practice bows. Supplies still proved insufficient until by the Statute of Westminster in 1472, every ship coming to an English port had to bring four bowstaves for every tun.
In 1507, the Holy Roman Emperor asked the Duke of Bavaria to stop cutting yew, but the trade was profitable, and in 1532, the royal monopoly was granted for the usual quantity "if there are that many". In 1562, the Bavarian government sent a long plea to the Holy Roman Emperor asking him to stop the cutting of yew, and outlining the damage done to the forests by its selective extraction, which broke the canopy and allowed wind to destroy neighbouring trees. In 1568, despite a request from Saxony, no royal monopoly was granted because there was no yew to cut, and the next year, Bavaria and Austria similarly failed to produce enough yew to justify a royal monopoly. Forestry records in this area in the 17th century do not mention yew, and it seems that no mature trees were to be had. The English tried to obtain supplies from the Baltic, but at this period, bows were being replaced by guns in any case.
Musical instruments