Taxus brevifolia

Pacific yew

Taxaceae

The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Coniferophyta (conifers). Class - Pinopsida. Order - Taxales. Family - Taxaceae (yew). Genus - Taxus L. Species -Taxus brevifolia Nutt.

Ecology: Pacific yew is present in many climax or near climax communities of the Pacific Northwest and northern Rocky Mountains. It is a particularly common component of old-growth grand fir, western redcedar, and Douglas-fir-western hemlock communities. Pacific yew increases in cover up to a stand age of at least 500 years in northwestern old growth Douglas-fir forests which are characterized by long fire-free intervals. Pacific yew is very tolerant of shade. It appears to require shade for establishment and can grow and develop under heavy forest canopies. The bark of Pacific yew contains a drug, taxol, that is being used in cancer research, so demand for yew bark by the National Cancer Institute has increased dramatically in recent years.

Identification

Shrubs or small trees to 15(--25) m, dioecious; trunk to 6(--12) dm diam., straight to contorted, fluted; crown open-conical. Bark scaly, outer scales purplish to purplish brown, inner ones reddish to reddish purple. Branches horizontal to drooping. Leaves 1--2.9 cm 1--3 mm, pale green abaxially, cuticular papillae present along stomatal bands, shiny yellow-green adaxially, epidermal cells as viewed in cross section of leaf mostly taller than wide. Seed ovoid, 2--4-angled, 5--6.5 mm.

Threats

In the WFDP: Competition for water and soil resources, especially during drought years, is a likely cause of mortality for Pacific yew in the WFDP. Pathogens affecting Pacific yew in the WFDP include: laminated root rot (Phellinus weirii) and Armillaria root rot (aka Honey fungus; Armillaria spp.).

Fire effects: Pacific yew has thin bark and is sensitive to heat damage. Plants are generally killed by even light ground fires, and this species is almost always eliminated from burned stands.

Reproduction

Flowering and Fruiting - Pacific yew is dioecious. Male strobili are stalked, bud-like, pale yellow, and composed of 6 to 12 filamentous stamens, each with 5 to 9 anthers. They are abundant on the underside of branch sprays and usually appear in May or June. Female strobili are less abundant, greenish, and composed of several scales. They also are borne on the underside of branches. The fruit is an ovoid-oblong seed about 8 mm long, partially enveloped by a fleshy, berrylike, scarlet, cup-shaped disk called an aril. Pollen is dispersed by wind in the spring.

Seed Production and Dissemination - Fruits ripen from August to October of the same year that flowering occurs. Fruits either drop to the ground or are taken from trees by birds or rodents. Birds devour the fleshy arils and void the seeds which remain viable. Chipmunks and squirrels often take only the seeds. Rodents and some birds-nuthatches, for example-cache yew seeds, thus creating the clusters of yew seedlings observed in some areas. The seed [poisonous] is about 6 mm long with a depressed hilum, bony inner coat, and membranous outer seedcoat. Pacific yew is a prolific seeder.

Vegetative Reproduction - Pacific yew is capable of layering and often sprouts from stumps or rootstocks after the top has been killed or the tree cut. Layering usually occurs after branches or tree tops have been pressed to the ground for a prolonged period by large fallen trees or limbs, although occasional old yew trees can be found surrounded by a ring of well rooted branches that were apparently held down only by their own weight and the weight of snow in the winter.

Species Distribution

Citation

USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

USFS Plant Database
Habeck, R. J. 1992. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

Silvics of North America
Burns, R.M., and B.H. Honkala. 1990. Silvics of North America (Volume 1: Conifers, Volume 2: Hardwoods). USDA Forest Service Agricultural Handbook 654.

Flora of North America
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+ vols. New York and Oxford.

The Jepson Herbarium
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA. $131.95, hardcover; 1600 pages. ISBN-13: 978-0520253124.

Burke Museum of Natural History and Culture
Burke Museum. 2016 [Online]. University of Washington.