''Taxus canadensis'', the Canada yew or Canadian yew, is a conifer native to central and eastern North America, thriving in swampy woods, ravines, riverbanks and on lake shores. Locally called simply "yew", this species is also referred to as American yew or ground-hemlock. Most of its range is well north of the Ohio River. It is, however, found as a rare ice age

relict A relict is a surviving remnant of a natural phenomenon. Biology A relict (or relic) is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas. Geology and geomorphology In geology, a r ...

in some coves of the Appalachian Mountains. The southernmost colonies are known from Ashe and Watauga Counties in

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and ...

Description and ecology

It is usually a sprawling shrub, rarely exceeding 2.5 m tall. It sometimes forms strong upright central leaders, but these cannot be formed from spreading branches, only from the original leader of the seedling plant. The shrub has thin scaly brown bark. The leaves ( needles) are lanceolate, flat, dark green, long and broad, arranged in two flat rows either side of the branch. The

seed cones A conifer cone (in formal botanical usage: strobilus, plural strobili) is a seed-bearing organ on gymnosperm plants. It is usually woody, ovoid to globular, including scales and bracts arranged around a central axis, especially in conifers an ...

are highly modified, each cone containing a single

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...

partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, open at the end. The seeds are eaten by

thrushes The thrushes are a passerine bird family, Turdidae, with a worldwide distribution. The family was once much larger before biologists reclassified the former subfamily Saxicolinae, which includes the chats and European robins, as Old World flyca ...

waxwing The waxwings are three species of passerine birds classified in the genus ''Bombycilla''. They are pinkish-brown and pale grey with distinctive smooth plumage in which many body feathers are not individually visible, a black and white eyestripe, ...

s and other

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, which disperse the (highly toxic) hard seeds undamaged in their droppings. The male cones are globose, 3 mm in diameter. It is a monoecious plant – one of the few in the genus.

Uses and traditions

All parts of Canadian yew, save the aril, are

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

; it is, however, thought to be of lower toxicity than '' T. baccata''. Tribes in its native range used small quantities of yew leaf tea topically or internally for a variety of ailments – notably rheumatism. Tribes are also been said to have used yew twigs in steam baths to help alleviate rheumatism. Again, the plant is quite toxic and modern

herbalists Herbal medicine (also herbalism) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. With worldwide research into pharmacology, some herbal medicines have been translated into modern remed ...

prefer safer, more effective herbs. ''Taxus canadensis'' is also being harvested in northern

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...

, Québec and Atlantic Canada as the plant is a source of the class of poisonous chemicals known as

taxane Taxanes are a class of diterpenes. They were originally identified from plants of the genus ''Taxus'' (yews), and feature a taxadiene core. Paclitaxel (Taxol) and docetaxel (Taxotere) are widely used as chemotherapy agents. Cabazitaxel was FDA ap ...

s, which have been a focus for

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

research. ''T. canadensis'' is much more abundant than the near-threatened ''

Taxus brevifolia ''Taxus brevifolia'', the Pacific yew or western yew, is a species of tree in the yew family Taxaceae native to the Pacific Northwest of North America. It is a small evergreen conifer, thriving in moisture and otherwise tending to take the form ...

'' (Pacific yew), and the "greens" (new growth) can be harvested sustainably every five years, instead of stripping the bark and killing the plant. The most abundant taxane in ''T. canadensis'' is 9-dihydro-13-acetylbaccatin III, which can be effectively converted to

10-deacetylbaccatin III 10-Deacetylbaccatins are a series of closely related natural organic compounds isolated from the yew tree (Genera ''Taxus''). 10-Deacetylbaccatin III is a precursor to the anti-cancer drug docetaxel (Taxotere). 10-deacetylbaccatin III 10-''O'' ...

, used in the production of

paclitaxel Paclitaxel (PTX), sold under the brand name Taxol among others, is a chemotherapy medication used to treat a number of types of cancer. This includes ovarian cancer, esophageal cancer, breast cancer, lung cancer, Kaposi's sarcoma, cervical canc ...

. Two additional taxanes have been identified from ''T. canadensis'', including 7β,10β,13α-triacetoxy-5α-(3'-dimethylamino-3'-phenylpropanoyl)oxy-2α-hydroxy-2(3→20)abeotaxa-4(20),11-dien-9-one and 2α,10β-diacetoxy-9α-hydroxy-5α-(3'-dimethylamino-3'-phenylpropanoyl)oxy-3,11-cyclotax-4(20)-en-13-one. Taxus canadensis 5443106

References

External links

* {{Taxonbar, from=Q1723511 canadensis Least concern plants Flora of West Virginia Trees of the Northeastern United States Plants described in 1785 Trees of Eastern Canada