Taxus baccata

Taxus baccata

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 common yew, or European yew.

Description

It is a small- to medium-sized evergreen tree, growing (exceptionally up to ) tall, with a trunk up to (exceptionally ) diameter. The bark is thin, scaly brown, coming off in small flakes aligned with the stem. The leaves are lanceolate, flat, dark green, long and 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 long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, 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 seed itself is extremely poisonous and bitter. The aril is not poisonous, and is gelatinous and very sweet tasting. The male cones are globose, diameter, and shed their pollen in early spring. It is mostly dioecious, but occasional individuals can be variably monoecious, or change sex with time.

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 unconfirmed 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.

Most 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, and eventually heart failure. However, death occurs so rapidly that many times the symptoms are missed.

Etymology

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.

Uses and traditions

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 Gallaecians 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.)

In 1021, Avicenna introduced the medicinal use of Taxus baccata L 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 yew is often found in church yards from England and Ireland to Galicia; some of these trees are exceptionally large (over 3 m diameter) and may be over 2,000 years old. 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.

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 mediaeval 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 is able to withstand compression while the sapwood is elastic and allows the bow to stretch. Both tend to return to their original straightness when the arrow is released. 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 1600s 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.

Yews are widely used in landscaping and ornamental horticulture. Well over 200 cultivars of Taxus baccata have been named. The most popular of these are the "Irish Yew" (Taxus 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". A special use of the yew is for topiary garden sculpture, a use not uncommon for many of the more elaborate gardens of England and Scotland.

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.

Literary references

  • The yew tree is an iconic reference in the poetry of Sylvia Plath, particularly in several poems from her collection of poetry Ariel. (See "The Moon and the Yew Tree", "Little Fugue", and "Daddy".)
  • In Shakesphere's Titus Andronicus, Act 2 Scene 3, Tamora the Goth queen exclaims: "No sooner had they told this hellish tale But straight they told me they would bind me here Unto the body of a dismal yew"
  • In the Irish myth "The Love of Chu Chulainn and Fand", the warrior and the goddess meet beneath a yew tree's head at every quarter moon.
  • John Keats refers to the yew in his "Ode on Melancholy", writing, "Make not your rosary of yew-berries, / Nor let the beetle, nor the death moth be / Your mournful Psyche, nor the downy owl / A partner in your sorrow's mysteries..." (lines 5-8).
  • In Alfred, Lord Tennyson's poem "In Memoriam: A.H.H." the yew above Arthur Hallam's grave is addressed: "Old yew, which graspest at the stones/ That name the underlying dead,/ Thy fibres net the dreamless head,/ Thy roots are wrapped about the bones" (II, ln. 1-4).
  • A Yew tree is featured prominently in William Wordsworth's poems "Lines Left Upon a Seat in a Yew Tree" and "Yew-Trees".
  • In Alexandre Dumas's novel, The Count of Monte Cristo, Edmond Dantès is imprisoned in the Château d'If, which literally translates to "Castle of the Yew" (If is a small island in France, and the name may or may not derive from the word which means yew).
  • George Bernard Shaw's Mrs. Warren's Profession uses a yew tree in the yard of Reverend Samuel Gardner.
  • In Section V of Little Gidding from T.S. Eliot's Four Quartets (the last section of the poem), Eliot claims: "The moment of the rose and the moment of the yew-tree/ Are of equal duration". In his poem, "Ash-Wednesday", he mentions the yew five times: "The silent sister veiled in white and blue/ Between the yewsNumber 1, behind the garden god, / Whose flute is breathless, bent her head and signed but/ spoke no word"; "Till the wind shake a thousand whispers from the yewNumber 2"; "Will the veiled sister between the slender/ Yew treesNumber 3 pray for those who offend her"; "But when the voices shaken from the yew-treeNumber 4 drift away/ Let the other yewNumber 5 be shaken and reply".
  • In J. R. R. Tolkien's The Silmarillion, Beleg Strongbow uses a bow made of yew. In The Hobbit, the eagle king complains of the men of Wilderland using bows made of yew to shoot at his people. Bard the Bowman uses a yew bow to fatally shoot the dragon Smaug.
  • The murderer in Agatha Christie's mystery A Pocket Full of Rye uses taxine (taxol), a poison derived from yew, to kill the victim. The victim lives at Yewtree Lodge.
  • In Ursula LeGuin's Earthsea series, both the wizard Ged and the Master Summoner carry staves of yew.
  • In J. K. Rowling's Harry Potter series, Voldemort uses a wand made of yew.
  • The Yew is the subject of Swedish author Gunnar D Hansson's "lyrical monography" Idegransöarna (The Yew-tree Islands, 1994, untranslated to English). Hansson explores the yew in its uses (medicinal, lyrical, in place-names, etc) and its historical meaning. He speculates about the yew, and weaves a tale of prose poems, essays and lyrics, about the yew; the book takes the reader close to the yew in its relation to Hittites, Vikings, medicine, Robin Hood, Christmas, heathendom, etymology and mythology.
  • The Great Chain of Being, which proposes a strict, hierarchical order for the beings (divine entities, animals, and plants) in the universe, designates the yew as the lowest form of tree among plants.
  • In Erin Hunter's Warriors novel series, yew berries are said to be poisonous to cats, and are referred to as "deathberries". Several vital plot points are based around yew, like Yellowfang intentionally feeding her son Brokentail yew berries and killing him. In a later book in the series, Darkstripe's disloyalty to his Clan becomes obvious when he feeds Sorrelkit, who had followed him and heard him plotting with Tigerstar, some yew berries in an attempt to kill her, but thanks to immediate medical attention, Sorrelkit survives and reveals what Darkstripe had been doing.
  • In Brian Jacques' novel Redwall, Constance the Badger uses a Yew Sapling to build a Crossbow, with which they hope to kill Cluny the Scourge.

Notes

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

See also

External links

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