Taxus baccata is a conifer native to western, central and southern Europe, northwest Africa, northern Iran and southwest Asia. It is the tree originally known as yew, though with other related trees becoming known, it may be now known as the English yew, or European yew.
Description
It is a small- to medium-sized evergreen tree, growing 10–20 metres (33–66 ft) (exceptionally up to 28 m/92 ft) tall, with a trunk up to 2 metres (6 ft 7 in) (exceptionally 4 m/13 ft) diameter. The bark is thin, scaly brown, coming off in small flakes aligned with the stem. The leaves are lanceolate, flat, dark green, 1–4 centimetres (0.39–1.6 in) long and 2–3 millimetres (0.079–0.12 in) broad, arranged spirally on the stem, but with the leaf bases twisted to align the leaves in two flat rows either side of the stem, except on erect leading shoots where the spiral arrangement is more obvious. The leaves are highly poisonous.
The seed cones are highly modified, each cone containing a single seed 4–7 millimetres (0.16–0.28 in) long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, 8–15 millimetres (0.31–0.59 in) long and wide and open at the end. The arils are mature 6–9 months after pollination, and with the seed contained are eaten by thrushes, waxwings and other birds, which disperse the hard seeds undamaged in their droppings; maturation of the arils is spread over 2–3 months, increasing the chances of successful seed dispersal. The seeds themselves are extremely poisonous and bitter, but are opened and eaten by some bird species including Hawfinches and Great Tits. The aril is not poisonous, and is gelatinous and very sweet tasting. The male cones are globose, 3–6 millimetres (0.12–0.24 in) diameter, and shed their pollen in early spring. It is mostly dioecious, but occasional individuals can be variably monoecious, or change sex with time.
Longevity
It is relatively slow growing, but can be very long-lived, with the maximum recorded trunk diameter of 4 metres probably only being reached in about 2,000 years. The potential age of yews is impossible to determine accurately and is subject to much dispute. There is rarely any wood as old as the entire tree, while the boughs themselves often hollow with age, making ring counts impossible. There are confirmed claims as high as 5,000-9,500 years, but other evidence based on growth rates and archaeological work of surrounding structures suggests the oldest trees (such as the Fortingall Yew in Perthshire, Scotland) are more likely to be in the range of 2,000 years. Even with this lower estimate, Taxus baccata is the longest living plant in Europe.
Significant trees
It is considered by several authors that the oldest yew tree in Spain is located in Bermiego, Asturias. It is known as «Teixu l'Iglesia» in the Asturian language. It is 15 meters tall with a trunk perimeter of 7 metres and a crown diameter of 10 meters. It was planted around 1160. It was declared Natural Monument on April 27, 1995 by the Asturian Government and is protected by the Plan of Natural Resources.
In Great Britain and in Normandy, there are many yews dating back around the year 1000 and some of them around 500. The Fortingall Yew is commonly believed to be the oldest one, with an estimated age between 2000 and 4000 years old, growing in a Scottish church yard. Other well-known yews include the Llangernyw Yew, Caesarsboom, and the Florencecourt Yew.
Toxin
Many parts of the tree are toxic, except the bright red aril surrounding the seed, enabling ingestion and dispersal by birds. The major toxin is the alkaloid taxane. The foliage remains toxic even when wilted or dried. Horses have the lowest tolerance, with a lethal dose of 200–400 mg/kg body weight, but cattle, pigs, and other livestock are only slightly less vulnerable. Symptoms include staggering gait, muscle tremors, convulsions, collapse, difficulty breathing, coldness and eventually heart failure. However, death occurs so rapidly that many times the symptoms are missed. Fatal poisoning in humans is very rare, only occurring after eating a lot of yew foliage. The lethal dose is reported to be between 50 and 100 grams. The wood is not poisonous at all.
Taxonomy and naming
The word yew is from Proto-Germanic *īwa-, possibly originally a loanword from Gaulish ivos, compare Irish ēo, Welsh ywen, French if (see Eihwaz for a discussion). Baccata is Latin for bearing red berries. The word yew as it was originally used seems to refer to the colour brown. The yew (μίλοσ) was known to Theophrastus, who noted its preference for mountain coolness and shade, it evergreen character and its slow growth.
On the other side, most romance languages kept the Latin word taxus : Italian tasso (Corsican tassu), Occitan teis (Catalan teix, Gasconic tech), Spanish tejo, Portuguese teixo (Galician teixu) and Romanian tisā, same root as toxic. In Russian, the same root (presumably borrowed from Romanian) is preserved: tiss (тис).
The common yew was one of the many species first described by Linnaeus. Along with around 30 other species, it is classified in the family Taxaceae, which is now firmly classified as a conifer in the order Pinales.
Uses and traditions
One of the world's oldest surviving wooden artifacts is a yew spear head, found in 1911 at Clacton-on-sea,in Essex, UK. It is estimated to be 450,000 years old.
In the ancient Celtic world, the yew tree (*eburos) had extraordinary importance; a passage by Caesar narrates that Catuvolcus, chief of the Eburones poisoned himself with yew rather than submit to Rome (Gallic Wars 6: 31). Similarly, Florus notes that when the Cantabrians were under siege by the legate Gaius Furnius in 22 BC, most of them took their lives either by the sword or by fire or by a poison extracted ex arboribus taxeis, that is, from the yew tree (2: 33, 50-51). In a similar way, Orosius notes that when the Astures were besieged at Mons Medullius, they preferred to die by their own swords or by the yew tree poison rather than surrender (6, 21, 1.)
Religion
In Asturian tradition and culture the yew tree has had a real link with the land, the people, the ancestors and the ancient religion. It was tradition on All Saints Day to bring a branch of a yew tree to the tombs of those who died recently so they will find the guide in their return to the Land of Shadows. The yew tree can be found near chapels, churches and cemeteries since ancient times as a symbol of the transcendence of death, and is usually found in the main squares of the villages where people celebrated the open councils that served as a way of general assembly to rule the village affairs.
The yew is often found in church yards from England, Ireland and France to Galicia. In France, the oldest yew trees are located in Norman church yards and a chapel was very often laid out in the hollow trunk. Some examples can be found in La Haye-de-Routot or La Lande-Patry. It is said, that up to 40 people could stand inside one of the La-Haye-de-Routot yew trees. Indeed, some of these trees are exceptionally large (over 3 m diameter) and may be over 2,000 years old. Sometimes monks planted yews in the middle of their cloister, like in Muckross Abbey (Ireland) or abbaye de Jumièges (France). Some ancient yew trees are located at St Mary the Virgin Church, Overton-on-Dee in Wales.
It has been suggested that the enormous sacred evergreen at the Temple at Uppsala was an ancient yew tree. The Christian church commonly found it expedient to take over these existing sacred sites for churches. It is sometimes suggested that these were planted as a symbol of long life or trees of death. An explanation that the yews were planted to discourage farmers and drovers from letting their animals wander into the burial grounds, with the poisonous foliage being the disincentive, may be intentionally prosaic. A more likely reason is that fronds and branches of yew were often used as a substitute for palms on Palm Sunday.
Medicines
In 1021, Avicenna introduced the medicinal use of T. baccata for phytotherapy in The Canon of Medicine. He named this herbal drug as "Zarnab" and used it as a cardiac remedy. This was the first known use of a calcium channel blocker drug, which were not in wide use in the Western world until the 1960s.
The precursors of chemotherapy drug Paclitaxel can be derived from the leaves of European Yew, which is a more renewable source than the bark of the Pacific Yew (Taxus brevifolia). This ended a point of conflict in the early 1990s; many environmentalists, including Al Gore, had opposed the harvesting of paclitaxel for cancer treatments. Docetaxel (another taxane) can then be obtained by semi-synthetic conversion from the precursors.
In the Central Himalayas, the plant is used as a treatment for breast and ovary cancer.
Longbows
Yew is also associated with Wales and England because of the longbow, an early weapon of war developed in northern Europe, and as the English longbow the basis for a medieval tactical system. Yew is the wood of choice for longbow making; the bows are constructed so that the heartwood of yew is on the inside of the bow while the sapwood is on the outside. This takes advantage of the natural properties of yew wood since the heartwood resists compression while the sapwood resists stretching. This increased the strength and efficiency of the bow. Much yew is knotty and twisted, so unsuitable for bowmaking; most trunks do not give good staves and even in a good trunk much wood has to be discarded.
The trade of yew wood to England for longbows was such 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 1350 there was a serious shortage, and Henry IV of England ordered his royal bowyer to enter private land and cut yew and other woods. 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. Richard III of England increased this to ten for every tun. This stimulated a vast network of extraction and supply, which formed part of royal monopolies in southern Germany and Austria. In 1483, the price of bowstaves rose from two to eight pounds per hundred, and in 1510 the Venetians would only sell a hundred for sixteen pounds. 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.
Horticultural cultivation
Today European Yew is widely used in landscaping and ornamental horticulture. Due to its dense, dark green mature foliage, and its tolerance of even very severe pruning, it is used especially for formal hedges and topiary. Its relatively slow growth rate means that in such situations it needs to be clipped only once per year (in late summer).
Well over 200 cultivars of T. baccata have been named. The most popular of these are the Irish Yew (T. baccata 'Fastigiata'), a fastigiate cultivar of the European Yew selected from two trees found growing in Ireland, and the several cultivars with yellow leaves, collectively known as "Golden Yew".
European Yew will tolerate growing in a wide range of soils and situations, including shallow chalk soils and shade, although in deep shade its foliage may be less dense. However it cannot tolerate waterlogging, and in poorly-draining situations is liable to succumb to the root-rotting pathogen Phytophthora cinnamomi.
In Europe, Taxus baccata grows naturally north to Molde in southern Norway, but it is used in gardens further north.
Conservation
Clippings from ancient specimens in the UK, including the Fortingall Yew, are being 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. The species is threatened by felling, partly due to rising demand from pharmaceutical companies, and disease.
Literary references
Notes
See also
References
- Chetan, A. and Brueton, D. (1994) The Sacred Yew, London: Arkana, ISBN 0-14-019476-2
- Conifer Specialist Group (1998) Taxus baccata, In: IUCN 2006/UCN Red List of Threatened Species, WWW page (Accessed 3 February 2007)
- Hartzell, H. (1991) The yew tree: a thousand whispers: biography of a species, Eugene: Hulogosi, ISBN 0-938493-14-0
- Simón, F. M. (2005) Religion and Religious Practices of the Ancient Celts of the Iberian Peninsula, e-Keltoi, v. 6, p. 287-345, ISSN 1540-4889 online
External links
Retrieved from :
http://en.wikipedia.org/wiki/Taxus_baccata
