Taxus brevifolia
From Freepedia
| Taxus brevifolia | ||||||||||||||
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| Image:PacificYew 7591.jpg Taxus brevifolia (Pacific Yew) foliage | ||||||||||||||
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| 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 close to the coast but with an isolated disjunct population in southeast British Columbia south to central Idaho.
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.
Uses
The chemotherapy drug paclitaxel, a chemotherapeutic drug used in breast and lung cancer, is derived from Taxus brevifolia. Over-harvesting for this drug has resulted in the Pacific Yew becoming an endangered species, though the drug is now produced semi-synthetically from cultivated yews, without the need to further endanger the wild populations.
