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| − | '''''Taxus''''' is a small [[genus]] of [[coniferous]] [[tree]]s or [[shrub]]s known as '''yews''' in the family [[Taxaceae]]. They are relatively slow-growing and can be very long-lived, and reach heights of {{convert|2.5|–|20|m|ft}}, with trunk girth averaging {{convert|5|m|ft}}.<ref>{{cite journal|last1=Moir|first1=Andy|title=The exceptional yew trees of England, Scotland and Wales|journal=Quarterly Journal of Forestry|date=2013|volume=2013|issue=2013|page=187|url=https://www.academia.edu/5865018/The_exceptional_yew_trees_of_England_Scotland_and_Wales|accessdate=19 July 2014|ref=1}}</ref> They have reddish [[Bark (botany)|bark]], lanceolate, flat, dark-green [[leaf|leaves]] {{convert|10|–|40|mm|in|frac=4}} long and {{convert|2|–|3|mm|in|frac=32|abbr=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.<ref name="taxol">{{eFloras|1|132355|Taxus|family=Taxaceae<!-- not currently used, but may be in future -->|first=Matthew H. |last=Hils}}</ref>
| + | [[Category:Conifers]] |
| − | | + | [[Category:Plants Keenan has eaten]] |
| − | == Morphology ==
| + | [[Category:Plants Keenan ate without Shakti]] |
| − | [[File:Taxus baccata MHNT seed.jpg|thumb|Seeds of ''Taxus baccata'']]
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| − | The [[conifer cone|seed cones]] are highly modified, each cone containing a single [[seed]] {{convert|4|–|7|mm|in|frac=32|abbr=in}} long partly surrounded by a modified scale which develops into a soft, bright red [[Berry (botany)|berry]]-like structure called an [[aril]], {{convert|8|–|15|mm|in|frac=32|abbr=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 [[Thrush (bird)|thrushes]], [[waxwing]]s and other [[bird]]s, 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 male cones are globose, {{convert|3|–|6|mm|in|frac=32|abbr=in}} across, and shed their [[pollen]] in early spring. Yews are mostly [[Plant sexuality|dioecious]], but occasional individuals can be variably [[Plant sexuality|monoecious]], or change sex with time.<ref name="taxol" />
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| − | All of the yews are very closely related to each other, and some botanists treat them all as subspecies or varieties of just one widespread species; under this treatment, the species name used is ''[[Taxus baccata]]'', the first yew described scientifically.<ref>{{cite web|url=http://www.botanicus.org/page/359061 |title=Caroli Linnaei ... Species plantarum |website=Botanicus.org |date= |accessdate=2016-11-17}}</ref> Other sources, however, recognize 9 species, for example the [http://www.theplantlist.org/tpl1.1/search?q=Taxus Plant List].
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| − | [[File:Taxus globosa foliage.jpg|left|thumb|Foliage of Mexican yew]]
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| − | The most distinct is the Sumatran yew (''T. sumatrana'', native to [[Sumatra]] and [[Sulawesi|Celebes]] north to southernmost [[China]]), distinguished by its sparse, sickle-shaped yellow-green leaves. The Mexican yew (''T. globosa'', native to eastern [[Mexico]] south to [[Honduras]]) is also relatively distinct with foliage intermediate between Sumatran yew and the other species. The Florida yew, Mexican yew and Pacific yew are all rare species listed as threatened or endangered.
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| − | All species of yew contain highly [[poison]]ous [[taxine]] [[alkaloid]]s, with some variation in the exact formula of the alkaloid between the species. All parts of the tree except the [[aril]]s contain the alkaloid. The arils are edible and sweet, but the seed is dangerously [[poison]]ous; unlike birds, the [[human]] stomach can break down the seed coat and release the taxanes into the body. This can have fatal results if yew 'berries' are eaten without removing the seeds first. Grazing animals, particularly [[cattle]] and [[horse]]s, are also sometimes found dead near yew trees after eating the leaves, though [[deer]] are able to break down the poisons and will eat yew foliage freely. In the wild, deer browsing of yews is often so extensive that wild yew trees are commonly restricted to cliffs and other steep slopes inaccessible to deer. The foliage is also eaten by the [[larva]]e of some [[Lepidoptera]]n [[insect]]s including the moth [[willow beauty]].
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| − | [[File:Taxus baccata MHNT flowers male.jpg|thumb|right|Male (pollen-producing) cones of ''Taxus baccata'']]
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| − | == Allergenic potential ==
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| − | All parts of a yew plant are toxic to humans with the exception of the yew berries (however, their seeds are toxic); additionally, male and monoecious yews in this genus release [[Cytotoxicity|cytotoxic]] pollen, which can cause headaches, lethargy, aching joints, itching, and skin rashes; it is also a trigger for asthma. These pollen granules are extremely small, and can easily pass through window screens. Male yews bloom and release abundant amounts of pollen in the spring; completely female yews only trap pollen while producing none.<ref name=Ogren>{{cite book|last1=Ogren|first1=Thomas|title=The Allergy-Fighting Garden|date=2015|publisher=Ten Speed Press|location=Berkeley, CA|isbn=978-1-60774-491-7|page=205}}</ref>
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| − | Yews in this genus are primarily separate-sexed, and males are extremely allergenic, with an [[OPALS (Ogren Plant Allergy Scale)|OPALS]] allergy scale rating of 10 out of 10. Completely female yews have an OPALS rating of 1, and are considered "allergy-fighting".<ref name="Ogren" />
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| − | == Uses and traditions ==
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| − | Yew [[wood]] is reddish brown (with whiter sapwood), and is very springy. It was traditionally used to make [[bow (weapon)|bows]], especially the [[longbow]].<ref>British yews tend to be to gnarly, and thus the wood for English longbows used at the [[Battle of Agincourt]] was imported from Spain or northern Italy. {{cite web|last=Eichhorn|first=Markus|title=Yew – The Sacred Tree|url=http://www.test-tube.org.uk/trees/video_yew.htm|work=Test Tube|publisher=[[Brady Haran]] for the [[University of Nottingham]]|date=September 2010}}</ref> [[Ötzi]], the Chalcolithic [[mummy]] found in 1991 in the Italian Alps, carried an unfinished bow made of yew wood. Consequently, it is not surprising that in [[Norse mythology]], the abode of the god of the bow, [[Ullr]], had the name [[Ydalir]] (Yew Dales). Most longbow wood used in northern Europe was imported from [[Iberian Peninsula|Iberia]], where climatic conditions are better for growing the knot-free yew wood required.<ref>{{cite web|url=http://www.iberianature.com/material/yew_spain.htm |title=Yews in Spain |website=www.iberianature.com |date= |accessdate=2 April 2018}}</ref> The yew longbow was the critical weapon used by the English in the defeat of the French [[cavalry]] at the [[Battle of Agincourt]], 1415. It is suggested that English [[parish]]es were required to grow yews and, because of the trees' toxic properties, they were grown in the only commonly enclosed area of a village – the churchyard.<ref>{{cite web|title=YEW TREES IN CHURCHYARDS|url=http://www.sacred-texts.com/neu/eng/osc/osc74.htm|website=Sacred-texts.com|accessdate=8 August 2011}}</ref> The yew tree can often be found in church graveyards and is symbolic of sadness. Such a representation appears in Lord Alfred Tennyson's poem "[[In Memoriam A.H.H.]]" (2.61–64).
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| − | The Yew can be very long-lived. The [[Fortingall Yew]] has been considered to be the oldest tree in Europe, at something over 2,000 years old. Tradition has it that [[Pontius Pilate]] slept under it while on duty before 30 AD. This has been topped by a tree in the churchyard of a small Welsh village called St Cynog. It has been dated to 5,000 years old by dendrologist Janis Fry.<ref>{{cite news|author=David Sanderson |url=http://www.thetimes.co.uk/tto/environment/article4141477.ece |title=Bronze Age tree survives wars (and the builders) to be claimed as Britain’s oldest |newspaper=[[The Times]] |date=2014-07-08 |accessdate=2016-11-17}}</ref> Such old trees usually consist of a circular ring of growths of Yew, since their heart has long since rotted away.
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| − | The [[Eihwaz]] [[rune]] is named after the yew, and sometimes also associated with the "evergreen" [[world tree]], [[Yggdrasil]].
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| − | [[File:English Yew close 250.jpg|right|thumb|Foliage of Irish yew; note the leaves spreading all round the erect shoots]]
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| − | Yews are widely used in landscaping and ornamental [[horticulture]]. Over 400 [[cultivar]]s of yews have been named, the vast majority of these being derived from European yew (''Taxus baccata'') or Japanese yew (''Taxus cuspidata''). The hybrid between these two species is ''[[Taxus media]]''. A popular fastigiate selection of the European yew (''Taxus baccata'' 'Fastigiata') is often called the Irish yew, which often complements the fact of the difficulties with common names. A few cultivars with yellow leaves that are being propagated, collectively are known as golden yews, which is another nomenclature blunder.
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| − | The [[Pacific yew]] (''Taxus brevifolia''), native to the [[Pacific Northwest]] of [[North America]], and the [[Canada yew]] (''Taxus canadensis'') were the initial sources of [[paclitaxel]] or [[Taxol]], a [[chemotherapy|chemotherapeutic]] drug used in [[breast cancer|breast]] and [[lung cancer]] treatment and, more recently, in the production of the Taxus [[drug eluting stent]] by [[Boston Scientific]]. [[Over-harvesting]] of the Pacific yew for paclitaxel led to fears that it would become an [[endangered species]], since the drug was extracted from the bark of the yew, the harvesting of which kills the tree in the process.<ref name="Gersmann 2011">{{cite news|last1=Gersmann|first1=Hanna|last2=Aldred|first2=Jessica|title=Medicinal tree used in chemotherapy drug faces extinction|url=https://www.theguardian.com/environment/2011/nov/10/iucn-red-list-tree-chemotherapy|accessdate=2017-02-15|work=The Guardian|date=10 November 2011}}</ref> However, methods were developed to produce the drug semi-synthetically from cultivated yews, without the need to further endanger the wild populations, and the Pacific yew is no longer at risk.<ref>{{cite web|publisher=Oregon Biodiversity Information Center|date=2010|title=Rare, Threatened and Endangered Species of Oregon. Institute for Natural Resources|location=[[Portland State University]], [[Portland, Oregon]]|url=http://orbic.pdx.edu/documents/2010-rte-book.pdf|format=PDF|deadurl=yes|archiveurl=https://web.archive.org/web/20110128214108/http://orbic.pdx.edu/documents/2010-rte-book.pdf|archivedate=2011-01-28|df=}}</ref> The more common Canada yew is also being successfully harvested in northern [[Ontario]], [[Quebec]] and [[New Brunswick]], and has become another major source of paclitaxel. Other yew species contain similar compounds with similar biochemical activity. [[Docetaxel]], an analogue of paclitaxel, is derived from the European yew (''Taxus baccata'').
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| − | [[File:Taxus baccata henrykow poland 01.jpg|thumb|Oldest Polish specimen of European yew (1200 years)]]
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| − | The yew tree is a frequent symbol in the Christian poetry of [[T. S. Eliot]], especially his ''[[Four Quartets]]''.
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| − | On January 18, 2008, the [[Botanic Gardens Conservation International]] (representing [[botanic gardens]] in 120 countries) stated that "400 medicinal plants are at risk of extinction, from over-collection and deforestation, threatening the discovery of future cures for disease." These included yew trees,<!-- The BGCI article mentions yews in Yunnan Province, China, which is not Pacific yew. --> whose bark is used for the cancer drug [[paclitaxel]].<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/health/7196702.stm |publisher=BBC NEWS |title=Medical plants 'face extinction' |date=19 January 2008}}</ref><ref>{{cite web |url=http://www.bgci.org/news-and-events/news/0479 |title=‘Miracle’ Cures Face Extinction |date=16 January 2008 |publisher=Botanic Gardens Conservation International}}</ref>
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| − | == Species and hybrids ==
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| − | [[File:4112 year Yew 3.jpg|thumb|4112 year old Taxus in Turkey]]
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| − | Names not linked have been mentioned in publications but not yet validated according to the International Code of Botanical Nomenclature
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| − | {{Div col}}
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| − | * Species Group: ''Baccata'' Group'''''
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| − | ** Alliance: ''Baccata'' Alliance'''
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| − | *** ''[[Taxus baccata]]'' European yew
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| − | *** ''[[Taxus contorta]]'' West Himalayan yew
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| − | *** ''[[Taxus fastigiata]]'' Irish yew
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| − | *** ''[[Taxus recurvata]]'' English yew
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| − | ** Alliance: ''Cuspidata'' Alliance'''
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| − | *** ''[[Taxus biternata]]'' Delicate branch yew
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| − | *** ''[[Taxus caespitosa]]'' Caespitosa yew
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| − | *** ''[[Taxus canadensis]]'' Canada yew
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| − | *** ''[[Taxus cuspidata]]'' Rigid branch yew, Japanese yew
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| − | *** ''[[Taxus umbraculifera]]'' Umbrelliform yew
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| − | * Species Group: ''Sumatrana'' Group
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| − | *** ''[[Taxus celebica]]'' Celebes yew
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| − | *** ''[[Taxus kingstonii]]'' Kingston yew
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| − | *** ''[[Taxus mairei]]'' Maire yew
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| − | *** ''[[Taxus sumatrana]]'' Sumatera yew
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| − | * Species Group: ''Wallichiana'' Group'''
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| − | ** Subgroup: ''Chinensis'' Subgroup'''
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| − | *** ''[[Taxus calcicola]]'' Asian limestone yew
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| − | *** ''[[Taxus chinensis]]'' China yew
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| − | *** ''[[Taxus obscura]]'' Obscure yew
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| − | *** ''Taxus ocreata'' Scaly yew
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| − | *** ''[[Taxus phytonii]]'' Phyton yew
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| − | *** ''Taxus rehderiana'' Rehder yew
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| − | *** ''Taxus scutata'' Scutaceous yew
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| − | ** Subgroup: ''Wallichiana'' Subgroup'''
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| − | *** ''[[Taxus brevifolia]]'' Pacific yew, western yew
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| − | *** ''[[Taxus floridana]]'' Florida yew
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| − | *** ''[[Taxus florinii]]'' Florin yew
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| − | *** ''[[Taxus globosa]]'' Mesoamerican yew
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| − | *** ''[[Taxus suffnessii]]'' Suffness yew
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| − | *** ''[[Taxus wallichiana]]'' Wallich yew, East Himalayan yew
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| − | {{div col end}}
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| − | '''Fossil (extinct) species'''
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| − | *{{extinct}}''Taxus engelhardtii'' – Oligocene, Bohemia, twig-leaves, similar to ''T.mairei''<ref name="Kvacek1984">Kvaček, Z. 1984. Tertiary taxads of NW Bohemia. 1982 Acta Univ. Carol., Geol., Pokorny 4: 471–491.</ref><ref name="Spjut2007">{{cite journal | last1 = Spjut | first1 = R. W. | year = 2007 | title = Taxonomy and nomenclature of ''Taxus'' (Taxaceae). A phytogeographical analysis of ''Taxus'' (Taxaceae) based on leaf anatomical characters | url = | journal = J. Bot. Res. Inst. Texas | volume = 1 | issue = 1| pages = 291–332 }} 203–289. ''T. brevifolia'' and ''T. globosa'' var. ''floridana'' thought to evolve from ancestral ''T. globosa'' by loss of stomata and papillae; ''T. canadensis'' recognized in Europe based on leaf fossils from late Tertiary deposits</ref>
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| − | * {{extinct}}''Taxus inopinata'' – Upper Miocene, leaf, similar to ''T. baccata''<ref>Corneanu, G. C. , M. Corneanu and R. Bercu. 2004. Comparison between some morpho-anatomical features at fossil vegetal species and at their actual correspondent species. Studia Universitatis Babeş-Bolyai, Geologia, XLIX: 77–84.</ref>
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| − | * {{extinct}}''[[Taxus masonii]]'' – Eocene [[Clarno Formation]]; Oregon, USA<ref name="Manchester1994">{{Cite journal |last1=Manchester |first1=S.R. |title=Fruits and Seeds of the Middle Eocene Nut Beds Flora, Clarno Formation, Oregon |year=1994 |journal=Palaeontographica Americana |volume=58 |pages=30–31}}</ref>
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| − | *{{extinct}}''Taxus schornii'' – Miocene, northern Idaho<ref name="Spjut2007" />
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| − | '''Commonly reported hybrids'''
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| − | ''[[Taxus × media]]'' = ''Taxus baccata'' × ''Taxus cuspidata''<ref>{{cite web|url=http://www.derkleinegarten.de/hecken1_eibe.htm |title=Eibenhecken :-) Pflanzung, Schnitt, Sorten - Taxus baccata |website=Derkleinegarten.de |date= |accessdate=2016-11-17}}</ref>
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| − | ''Taxus × hunnewelliana'' = ''Taxus cuspidata'' × ''Taxus canadensis''<ref>{{cite web|url=http://www.worldbotanical.com/TAXNA.HTM |title=Overview of the genus Taxus, Taxonomy, Nomenclature, and Ovulate Shoots |website=Worldbotanical.com |date= |accessdate=2016-11-17}}</ref>
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| − | ==References==
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| − | {{Reflist|30em}}
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| − | ==External links==
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| − | {{Taxonbar|from=Q27355}}
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| − | [[Category:Taxus| ]] | |
| − | [[Category:Conifer genera]] | |
| − | [[Category:Dioecious plants]] | |
