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 of a shrub.
Description
A small
evergreen conifer (sometimes appearing as a
shrub),
the Pacific yew grows to tall and with a trunk up to in diameter, rarely more. In some instances, trees with heights in excess of occur in parks and other protected areas, quite often in gullies. The tree is extremely slow growing, and has a habit of rotting from the inside, creating hollow forms. This makes it difficult and sometimes impossible to make accurate
Dendrochronology to determine a specimen's true age. Often damaged by succession of the forest, it usually ends up in a squat, multiple-leader form, able to grow new sprouts from decapitated stumps.
In its shrub form, sometimes called "yew brush", it can reproduce vegetatively via layering.
It has thin, scaly bark, red then purplish-brown,
The conifer cone are highly modified, each cone containing a single seed long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril,
Taxonomy
Varieties
Taxus brevifolia var. reptaneta
T. brevifolia var.
reptaneta (thicket yew) is a shrub variety that generally occurs in the mid to upper elevation range of the typical variety, at its southernmost occurrence in the Klamath Mountains region, and at lower elevations further north.
[Spjut, R. W. 2007. Taxonomy and nomenclature of Taxus. J. Bot. Res. Inst. Texas 1(1): 203–289.] It is distinguished from young trees of the typical variety (var.
brevifolia) by its stems initially creeping along the ground for a short distance before ascending (curving) upwards and by the branches growing off to one side of the stem, usually the upper side.
[Web page, World Botanical Associates, Taxus brevifolia var. reptaneta; http://www.worldbotanical.com/taxus_brevifolia_var_reptaneta.htm. Retrieved 9 Dec 2014] The epithet
reptaneta is from the Latin
reptans which means "creeping, prostrate, and rooting",
[Stearn, W. T. 1983. Botanical Latin. 3rd ed. David & Charles, London] which is exactly what this variety does; in rooting it forms yew thickets; hence, the epithet
reptaneta (-
etum means "collective place of growth") and hence the common name, thicket yew.
Unlike the typical variety, thicket yew grows in abundance on open sunny avalanche shoots or ravines as well as in the forest understory. It also occurs along forest margins. In northwestern Montana, a variant of the thicket yew does not ascend upwards; rather, it remains along the ground.
T. brevifolia var. reptaneta has been described as synonymous with typical yew (var. brevifolia). Though the two varieties may be genetically distinct, some botanists only use this taxon to describe different geographical ranges. For example, Taxus mairei var. speciosa, which occurs with the typical variety in southern China in 10 of 13 provinces, was rejected for the lack of a "geographic reason" for recognition[Möller M, Gao L-M, Mill RR, Liu J, Zhang D-Q, Poudel RC, Li D-Z, 2013. A multidisciplinary approach reveals hidden taxonomic diversity in the morphologically challenging Taxus wallichiana complex. Taxon 62: 1161–1177.] though it appears genetically distinct.[Gao L-M, Möller M, Zhang X-M, Hollingsworth ML, Liu J, Mill RR, Gibby M, Li D-Z, 2007. High variation and strong phylogeographic pattern among cpDNA haplotypes in Taxus wallichiana (Taxaceae) in China and North Vietnam. Molec. Ecol. 16: 4684–4698.] T. brevifolia var. reptaneta has also been proposed to be elevated to a subspecies, despite that rank being used to define geographically separated groups of T. baccata.[Pilger R, 1903. Taxaceae-Taxoideae—Taxeae. Taxus. In: Das Pflanzenreich IV (Engler A. ed.): 110–116.]
Taxus brevifolia var. polychaeta
Typical
T. brevifolia, like most species in the genus, usually produces a single ovule on a complex scaly shoot, composed of a primary shoot and a secondary short shoot. To the casual observer they appear as one funnelform shoot with an ovule at the apex.
[Florin R, 1951. Evolution in cordaites and conifers. Acta Horti Berg. 16: 285–388, plate] T. brevifolia var.
polychaeta differs from var.
brevifolia in producing a relatively longer primary shoot
with as many five secondary shoots.
[Web page, World Botanical Associates, Overview of the genus Taxus, http://www.worldbotanical.com/TAXNA.HTM, retrieved 9 Dec 2014] The epithet,
polychaeta, is in reference to the primary shoot resembling a
polychaete worm; hence, its common name 'worm cone yew'. Variety
polychaeta appears to be relatively rare. It may have been
Local extinction from the type locality—around Mud Bay near Olympia, Washington—as a result of urban expansion. It is also known from Northern Idaho and Sonoma County, California.
[Web page, World Botanical Associates, Taxus brevifolia var. polychaeta; http://www.worldbotanical.com/taxus_brevifolia_var_polychaeta.htm; retrieved 9 Dec 2014]
As in the case with thicket yew, worm yew has been indicated to be the same as the typical variety, but again there are no specific studies to support this conclusion. The authority of thicket yew and worm cone yew has been involved in the study of Taxus for 25 years at the time the varieties were described.[Spjut, R. W. 1977. USDA, ARS Memorandum, July 14]. Taxus brevifolia (Taxaceae) reviewed by GMC (Gudrun M. Christensen). A review of literature on taxonomy, ecology, and geographical distribution of the species, including its description, summary of geographical distribution by state or province, and literature reviewed. Distributed periodically during 1981-1992 by the National Cancer Institute to prospective suppliers, without reference to the author, for solicitations of contract bids on up to 30 tons of bark.]
Similar species
Yew foliage is very similar to that of
Sequoia sempervirens, the coastal redwood.
Distribution and habitat
Pacific yew is
native species to the Pacific Northwest. It ranges from southernmost
Alaska south to Northern California, mostly in the Pacific Coast Ranges, but with isolated disjunct populations in southeast
British Columbia and in
Northern Idaho.
[
][Hitchcock, C. H., A.J. Cronquist, F. M. Ownbey & J. W. Thompson. 1969. Vascular Cryptogams, Gymnosperms, and Monocotyledons. 1: 1–914. In C. L. Hitchcock Vascular Plants of the Pacific Northwest. University of Washington Press, Seattle.][Hultén, E. 1968. Flora Alaska i–xxi, 1–1008. Stanford University Press, Stanford.][Moss, E. H. 1983. Flora of Alberta (ed. 2) i–xii, 1–687. University of Toronto Press, Toronto.][Munz, P. A. & D. D. Keck. 1959. California Flora 1–1681. University of California Press, Berkeley.][Welsh, S. L. 1974. Anderson's Flora of Alaska and Adjacent Parts of Canada i–xvi, 1–724. Brigham Young University Press, Provo.] It grows in varying types of environments; however, in drier environments it is mostly limited to stream-side habitats, whereas in moist environments it will grow up onto slopes and ridgetops,
at least as high in altitude as above sea level.
Pacific yew is
shade tolerant, but can also grow in sun.
The tree's shade tolerance allows it to form an
understory, which means that it can grow along streams providing shade to maintain water temperature.
Ecology
Birds eat the fruit cups and spread the seeds.
Moose feed on the tree in winter in forests of the
Rocky Mountains.
Toxicity
Many parts of yews are poisonous and can be fatal if eaten, including the seed which should not even be chewed.
Uses
Traditionally, the resilient and rot-resistant wood was used by Native Americans to make tools, bows (backed with sinew), arrows, and canoe paddles.
Other purposes for yew included making harpoons, fishhooks, wedges, clubs, spoons, drums, snowshoes, and arrowheads.
The foliage and bark was used for medicinal purposes.
Members of the Pit River Tribe would sell this plant to the
Yuki people.
[Chestnut, V. K. 1902 Plants Used by the Indians of Mendocino County, California. Contributions from the U.S. National Herbarium 7:295-408. (p. 305)] The Concow tribe calls the tree
yōl'-kō (
Konkow language).
Modern-day longbow makers report that a very small percentage of yew trees are of a grain suitable for their craft.
The juicy red cup around the seed seems to be edible (but not the toxic seed within),
The chemotherapy drug paclitaxel (taxol), used in breast cancer, ovarian cancer, and lung cancer treatment, can be derived from T. brevifolia
Notes
Further reading
-
Heiken, D. (1992). The Pacific Yew and Taxol: Federal management of an emerging resource. Journal of Environmental Law and Litigation 7: 175.
External links
