Taxus brevifolia

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iTaxus brevifolia

Taxus brevifolia (Pacific Yew) foliage

Scientific classification

Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Taxaceae
Genus:	Taxus
Species:	T. brevifolia

Binomial name

Taxus brevifolia
Nutt.

Taxus brevifolia (Pacific Yew or Western Yew) is a conifer native to the Pacific Northwest of North America, from southernmost Alaska south to central California, mostly in the Pacific Coast Ranges, but with an isolated disjunct population in southeast British Columbia south to central Idaho.

Pacific Yew foliage underside

Pacific Yew form

It is a small to medium-sized evergreen tree, growing 10-15 m tall and with a trunk up to 50 cm diameter, rarely more.

It has thin scaly brown bark. The leaves are lanceolate, flat, dark green, 1-3 cm long and 2-3 mm 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 seed cones are highly modified, each cone containing a single seed 4-7 mm long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, 8-15 mm 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 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 male cones are globose, 3-6 mm diameter, and shed their pollen in early spring. It is mostly dioecious, but occasional individuals can be variably monoecious, or change sex with time.

[edit] Uses

The chemotherapy drug paclitaxel, used in breast and lung cancer treatment, is derived from Taxus brevifolia. Over-harvesting for production of this drug has resulted in the Pacific Yew becoming a rare species, despite the fact the drug can be produced semi-synthetically from cultivated yews. The pharmaceutical industry is also still exploiting closely-related wild yew species in India and China for the same purposes, which threatens some of those species as well.