Taxus Baccata

''Taxus baccata'' is a species of evergreen tree in the family Taxaceae, native to western, central and southern Europe (including Britain and Ireland), northwest Africa, northern Iran, and southwest Asia.Rushforth, K. (1999). ''Trees of Britain and Europe''. Collins . It is the tree originally known as yew, though with other related trees becoming known, it may now be known as common yew, English yew, or European yew. It is primarily grown as an ornamental. Most parts of the plant are poisonous, with toxins that can be absorbed through inhalation and through the skin; consumption of even a small amount of the foliage can result in death.

Taxonomy and naming

The word ''yew'' is from Proto-Germanic ''*īwa-'', possibly originally a loanword from Gaulish ''*ivos'', compare Breton ''ivin,'' Irish '' ēo'', Welsh ''ywen'', French '' if'' (see Eihwaz for a discussion). In German it is known as ''Eibe''. ''Baccata'' is Latin for ''bearing 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, its evergreen character and its slow growth.

Most Romance languages, with the notable exception of French (''if''), kept a version of the Latin word ''taxus'' (Italian ''tasso'', Corsican ''tassu'', Occitan ''teis'', Catalan ''teix'', Gasconic ''tech'', Spanish ''tejo'', Asturian ''texu'', Portuguese ''teixo'', Galician ''teixo'' and Romanian ''tisă'') from the same root as ''toxic''. In Slavic languages, the same root is preserved: Polish ''cis'', Ukrainian, Slovakian and Russian ''tis'' (''тис''), Serbian-Croatian-Bosnian-Montenegrin ''tisa''/''тиса'', ''tis'', Slovenian ''tisa''. Albanian borrowed it as ''tis''.

In Iran, the tree is known as ''sorkhdār'' ( fa, سرخدار, literally "the red tree").

The common yew was one of the many species first described by Linnaeus. It is one of around 30 conifer species in seven genera in the family Taxaceae, which is placed in the order Pinales.

Description

Yews are small to medium-sized evergreen trees, growing (exceptionally up to ) tall, with a trunk up to (exceptionally ) in diameter. The bark is thin, scaly 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 leaves are poisonous.Mitchell, A. F. (1972). ''Conifers in the British Isles''. Forestry Commission Booklet 33.

The seed cones are modified, each cone containing a single seed, which is long, and partly surrounded by a fleshy scale which develops into a soft, bright red berry-like structure called an aril. The aril is long and wide and open at the end. The arils mature 6 to 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 to 3 months, increasing the chances of successful seed dispersal.

The seeds themselves are poisonous and bitter, but are opened and eaten by some bird species, including hawfinches, greenfinches, and great tits. The aril is not poisonous; it is gelatinous and very sweet tasting. The male cones are globose, in diameter, and shed their pollen in early spring. Yews are mostly dioecious, but occasional individuals can be variably monoecious, or change sex with time.Dallimore, W., & Jackson, A. B. (1966). ''A Handbook of Coniferae and Ginkgoaceae'' 4th ed. Arnold.

Distribution and habitat

''T. baccata'' 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. A few populations are also 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.

''T. baccata''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 England it grows best in 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.

''T. baccata'' 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.

''T. baccata'' normally appears individually or in small groups within the understory, but also forms stands throughout its range, such as in sheltered calcareous sites. ''T. baccata'' 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.

In centuries past ''T. baccata'' was exterminated from many woodlands as a poisonous hazard to the cattle and horses that often grazed in the woods. Rabbits and deer however have a level of immunity to the poisonous alkaloids, and the seeds are dispersed by birds, with thrushes greatly enjoying the fruit. It also regenerates readily from stumps and roots, even when ancient and hollow.

Longevity

''Taxus baccata'' can reach 400 to 600 years of age. Some specimens live longer but the age of yews is often overestimated. Ten yews in Britain are believed to predate the 10th century. 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 become hollow with age, making ring counts impossible. Evidence based on growth rates and archaeological work of surrounding structures suggests the oldest yews, such as the Fortingall Yew in Perthshire, Scotland, may be in the range of 2,000 years,Harte, J. (1996). How old is that old yew? ''At the Edge'' 4: 1–
online
Kinmonth, F. (2006). Ageing the yew – no core, no curve? ''International Dendrology Society Yearbook'' 2005: 41–46.Lewington, A., & Parker, E. (1999). ''Ancient Trees: Trees that Live for a Thousand Years''. London: Collins & Brown Ltd. placing them among the oldest plants in Europe. One characteristic contributing to yews' longevity is that unlike most other trees they are able to split under the weight of advanced growth without succumbing to disease in the fracture. Another is their ability to give rise to new epicormic and basal shoots from cut surfaces and low on their trunks, even in old age.

Significant trees

The Fortingall Yew in Perthshire, Scotland, has the largest recorded trunk girth in Britain and experts estimate it to be 2,000 to 3,000 years old, although it may be a remnant of a post-Roman Christian site and around 1,500 years old. The Llangernyw Yew in Clwyd, Wales, can be found at an early saint site and is about 1,500 years old. Other well known yews include the Ankerwycke Yew, the Balderschwang Yew, the Caesarsboom, the Florence Court Yew, and the Borrowdale Fraternal Four, of which poet William Wordsworth wrote. The Kingley Vale National Nature Reserve in West Sussex has one of Europe's largest yew woodlands.

The oldest specimen in Spain is located in Bermiego, Asturias. It is known as in the Asturian language. It stands tall with a trunk diameter of and a crown diameter of . It was declared a Natural Monument on April 27, 1995, by the Asturian Government and is protected by the Plan of Natural Resources. Contains Word document "Monumento Natural Teixu de Bermiego".

A unique forest formed by ''Taxus baccata'' and European box (''Buxus sempervirens'') lies within the city of Sochi, in the Western Caucasus.

The oldest Irish Yew (''Taxus baccata'' 'Fastigiata'), the Florence Court Yew, still stands in the grounds of the Florence Court estate in County Fermanagh, Northern Ireland. The Irish Yew has become ubiquitous in cemeteries across the world, and it is believed that all known examples are from cuttings from this tree.

Toxicity

The entire yew bush is poisonous, with the exception of the aril (the red flesh of the berry covering the seed). Yews contain numerous toxic compounds, including "at least ten alkaloids, nitriles (cyanogenic glycoside esters), ephedrine", and their essential oil, but the most important toxins are taxine alkaloids, cardiotoxic chemical 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 6 hours after the point of ingestion. The European yew is one of the most toxic species in the genus, along with the Japanese yew, ''T. cuspidata''.

Yew poisonings are relatively common in both domestic and wild animals which consume the plant accidentally, resulting in "countless fatalities in livestock". Taxines are also absorbed efficiently via the skin. ''Taxus'' species should thus be handled with care and preferably with gloves.

"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.

Allergenic potential

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. The pollen, like most species', easily passes through window screens.

While yew pollen does not contain sufficient taxine alkaloids to cause poisoning, its allergenic potential has been implicated in adverse reactions to paclitaxel treatment.

Traditions

Historic suicides

In the ancient Celtic world, the yew tree (''*eburos'') had extraordinary importance; a passage by Caesar narrates that Cativolcus, 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 sword, fire, or 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 yew poison rather than surrender (6, 21, 1).

Place names

The word ''York'' ( non, Jórvík) is derived from the Brittonic name ( Latinised variously as , , or ), a combination of "yew-tree" (compare Old Irish "yew-tree" (Irish , , ; Scottish Gaelic ), Welsh "alder buckthorn", Breton "alder buckthorn") and a suffix of appurtenance

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