''Taxus brevifolia'', the Pacific yew or western yew, is a
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of tree in the yew
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Taxaceae
Taxaceae (), commonly called the yew family, is a coniferous family (biology), family which includes six Extant taxon, extant and two extinct genera, and about 30 species of plants, or in older interpretations three genera and 7 to 12 species.
...
native to the
Pacific Northwest
The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...
of
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
. It is a small
evergreen
In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...
conifer
Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
, thriving in moisture and otherwise tending to take the form of a
shrub
A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
.
Description
A small
evergreen
In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...
conifer
Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
(sometimes appearing as a
shrub
A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
),
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
ring counts to determine a specimen's true age. Often damaged by
succession
Succession is the act or process of following in order or sequence.
Governance and politics
*Order of succession, in politics, the ascension to power by one ruler, official, or monarch after the death, resignation, or removal from office of ...
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
Layering can refer to:
* Layering (horticulture), a means of vegetative propagation
* Layering (finance), a strategy in high frequency trading
* Layering (linguistics), a principle by which grammaticalisation can be detected
* Surface layering ...
.
It has thin, scaly
bark
Bark may refer to:
Common meanings
* Bark (botany), an outer layer of a woody plant such as a tree or stick
* Bark (sound), a vocalization of some animals (which is commonly the dog)
Arts and entertainment
* ''Bark'' (Jefferson Airplane album), ...
, red then purplish-brown,
covering a thin layer of off-white sap wood with a darker
heartwood
Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...
that varies in color from brown to a purplish hue to deep red, or even bright orange when freshly cut.
The
leaves
A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
are lanceolate, flat, dark green, long
and 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
In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
long partly surrounded by a modified scale which develops into a soft, bright red
berry
A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit although many pips or seeds may be present. Common examples of berries in the cul ...
-like structure called an
aril
An aril (), also called arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode, or false aril, is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ova ...
,
long and wide and open at the end. The arils are mature 6–9 months after pollination. The seeds contained in the arils are eaten by
thrushes and other
bird
Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
s, 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, diameter, and shed their
pollen
Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
in early spring. It is mostly
dioecious
Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...
, but occasional individuals can be variably
monoecious
Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system comparable with gynomonoecy, andromonoecy and trimonoecy, and contras ...
, or change sex with time.
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
The Klamath Mountains are a rugged and lightly populated mountain range in northwestern California and southwestern Oregon in the western United States. As a mountain system within both the greater Pacific Coast Ranges and the California Coast R ...
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. The epithet ''reptaneta'' is from the Latin ''reptans'' which means "creeping, prostrate, and rooting", 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.
This is probably the ancestral form; the upright form with branches along the upper side would be the expected growth pattern that might evolve from one with stems that strictly creep along the ground since branches can only arise from the upper surface.
''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, ''
T. 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 though it appears genetically distinct. ''T. brevifolia'' var. ''reptaneta'' has also been proposed to be elevated to a
subspecies
In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
, despite that rank being used to define geographically separated groups of ''T. baccata''.
''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. ''T. brevifolia'' var. ''polychaeta'' differs from var. ''brevifolia'' in producing a relatively longer primary shoot
with as many five secondary shoots. The epithet, ''polychaeta'', is in reference to the primary shoot resembling a
polychaete
Polychaeta () is a paraphyletic class of generally marine Annelid, annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called c ...
worm; hence, its common name 'worm cone yew'. Variety ''polychaeta'' appears to be relatively rare. It may have been
extirpated
Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions.
Local extinctions mark a chan ...
from the type locality—around
Mud Bay near
Olympia, Washington
Olympia is the capital city of the U.S. state of Washington. It had a population of 55,605 at the 2020 census, making it the state of Washington's 23rd-most populous city. Olympia is the county seat of Thurston County, and the central city ...
—as a result of urban expansion. It is also known from Northern Idaho and
Sonoma County, California
Sonoma County ( ) is a county located in the U.S. state of California. As of the 2020 United States census, its population was 488,863. Its seat of government and largest city is Santa Rosa.
Sonoma County comprises the Santa Rosa-Petaluma ...
.
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.
Similar species
Yew foliage is very similar to that of ''
Sequoia sempervirens
''Sequoia sempervirens'' ()''Sunset Western Garden Book,'' 1995: 606–607 is the sole living species of the genus ''Sequoia (genus), Sequoia'' in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast ...
'', the coastal redwood.
Distribution and habitat
Pacific yew is
native
Native may refer to:
People
* '' Jus sanguinis'', nationality by blood
* '' Jus soli'', nationality by location of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Nat ...
to the
Pacific Northwest
The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...
. It ranges from southernmost
Alaska
Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
south to
Northern California
Northern California (commonly shortened to NorCal) is a geocultural region that comprises the northern portion of the U.S. state of California, spanning the northernmost 48 of the state's List of counties in California, 58 counties. Northern Ca ...
, mostly in the
Pacific Coast Ranges
The Pacific Coast Ranges (officially gazetted as the Pacific Mountain System in the United States; ; ) are the series of mountain ranges that stretch along the West Coast of North America from Alaska south to Northern and Central Mexico. Althoug ...
, but with isolated
disjunct populations in southeast
British Columbia
British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
and in
Northern Idaho.
[
] 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
In ecology, shade tolerance is a plant's ability to tolerate low light levels. The term is also used in horticulture and landscaping, although in this context its use is sometimes imprecise, especially in labeling of plants for sale in nursery (ho ...
, but can also grow in sun.
The tree's shade tolerance allows it to form an
understory
In forestry and ecology, understory (American English), or understorey (English in the Commonwealth of Nations, Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the Canopy (biology), forest ca ...
, 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
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...
.
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
Club may refer to:
Arts, entertainment, and media
* Club (magazine), ''Club'' (magazine)
* Club, a ''Yie Ar Kung-Fu'' character
* Clubs (suit), a suit of playing cards
* Club music
* "Club", by Kelsea Ballerini from the album ''kelsea''
Brands a ...
, 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
Ukiah. The
Concow tribe calls the tree yōl’-kō (
Konkow language).
Modern-day
longbow
A longbow is a type of tall bow that makes a fairly long draw possible. Longbows for hunting and warfare have been made from many different woods in many cultures; in Europe they date from the Paleolithic era and, since the Bronze Age, were mad ...
makers report that a very small percentage of yew trees are of a grain suitable for their craft.
The
Japanese have used the wood for decorative purposes,
and the Taiwanese have valued it as well.
The juicy red cup around the seed seems to be edible (but not the toxic seed within),
with a mild cherry
jello-like flavour.
The berry is said to have a sweet taste but slimy texture, while the leaves, bark and seed are extremely poisonous and should not be consumed.
The
chemotherapy
Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...
drug
paclitaxel
Paclitaxel, sold under the brand name Taxol among others, is a chemotherapy medication used to treat ovarian cancer, esophageal cancer, breast cancer, lung cancer, Kaposi's sarcoma, cervical cancer, and pancreatic cancer. It is administered b ...
(taxol), used in
breast
The breasts are two prominences located on the upper ventral region of the torso among humans and other primates. Both sexes develop breasts from the same embryology, embryological tissues. The relative size and development of the breasts is ...
,
ovarian, and
lung cancer
Lung cancer, also known as lung carcinoma, is a malignant tumor that begins in the lung. Lung cancer is caused by genetic damage to the DNA of cells in the airways, often caused by cigarette smoking or inhaling damaging chemicals. Damaged ...
treatment, can be derived from ''T. brevifolia''
and other species of yew. As it was already becoming scarce when its chemotherapeutic potential was realized around the 1990s, the Pacific yew was never commercially harvested from its habitat at a large scale; the widespread use of the paclitaxel was enabled circa 2003 when a semi-synthetic pathway was developed from extracts of cultivated yews of other species.
Gallery
Image: PacificYew_7684.jpg, Pacific yew foliage underside
Image: PacificYew_8544.jpg, Pacific yew form
Image: PacificYew_8538.jpg, Pacific yew foliage
Image:PacificYew_7790.jpg, Pacific yew mat form
Image: PacificYew_8566.jpg, Pacific yew bark
Image: Pacific_yew.jpg, Color variations of bark on Pacific yew
Notes
References
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
*
US Forest Service: ''Taxus brevifolia''(pdf file)
{{Authority control
brevifolia
Flora of Alaska
Flora of Alberta
Flora of British Columbia
Flora of California
Flora of Idaho
Flora of Montana
Flora of Oregon
Flora of Washington (state)
Trees of Northern America
Medicinal plants of North America