Western Hemlock
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''Tsuga heterophylla'', the western hemlock or western hemlock-spruce, is a species of hemlock native to the west coast of North America, with its northwestern limit on the
Kenai Peninsula The Kenai Peninsula ( Dena'ina: ''Yaghenen'') is a large peninsula jutting from the coast of Southcentral Alaska. The name Kenai (, ) is derived from the word "Kenaitze" or "Kenaitze Indian Tribe", the name of the Native Athabascan Alaskan trib ...
, Alaska, and its southeastern limit in northern
Sonoma County, California Sonoma County () is a county (United States), county located in the U.S. state of California. As of the 2020 United States Census, its population was 488,863. Its county seat and largest city is Santa Rosa, California, Santa Rosa. It is to the n ...
.Farjon, A. (1990). ''Pinaceae. Drawings and Descriptions of the Genera''. Koeltz Scientific Books .Gymnosperm Database
''Tsuga heterophylla''
The
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
species name means 'variable leaves'.


Description

Western hemlock is a large
evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...
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 single ...
growing to tall, exceptionally ,Tallest Hemlock, M. D. Vaden, Arborist
''Tallest known Hemlock, Tsuga heterophylla''
/ref> and with a trunk diameter of up to . It is the largest species of hemlock, with the next largest (
mountain hemlock ''Tsuga mertensiana'', known as mountain hemlock, is a species of hemlock native to the west coast of North America, found between Southcentral Alaska and south-central California. Description ''Tsuga mertensiana'' is a large evergreen conifer ...
) reaching a maximum height of . The bark is brown, thin, and furrowed (outwardly appearing similar to that of Douglas-fir). The crown is a very neat broad conic shape in young trees with a strongly drooping lead shoot, becoming cylindrical in older trees, which may have no branches in the lowest . At all ages, it is readily distinguished by the pendulous branchlet tips. The shoots are very pale buff-brown, almost white, with pale pubescence about long. The leaves are needle-like, long and broad, strongly flattened in cross-section, with a finely
serrate Serration is a saw-like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than a smooth blade or other edge, the applied pr ...
d margin and a bluntly acute apex. They are mid to dark green above; the underside has two distinctive white bands of
stoma In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...
ta with only a narrow green midrib between the bands. They are arranged spirally on the shoots but are twisted at the base to lie in two ranks on either side of the shoot. The
cones A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines conn ...
appear on trees over about 25 years old; they are small, pendulous, slenderly cylindrical, long and broad when closed, opening to broad. They have 15–25 thin, flexible scales long. The immature cones are green, maturing gray-brown 5–7 months after pollination. They are usually plentiful enough to cover the ground beneath the tree. The abundant
seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
s are brown, long, with a slender, pale-brown wing measuring long. Initial growth is slow; one-year-old seedlings are commonly only tall, and two-year-old seedlings tall. Once established, saplings in full light may have an average growth rate of (rarely ) annually until they are tall, and in good conditions still annually when tall. The tallest specimen, tall, is in
Prairie Creek Redwoods State Park Prairie Creek Redwoods State Park is a state park, located in Humboldt County, California, near the town of Orick and 50 miles (80 km) north of Eureka. The 14,000 acre (57 km²) park is a coastal sanctuary for old-growth Coast Redw ...
,
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
(United States). The species is long-lived, especially at higher elevations, with trees over 1,200 years old known.


Habitat and ecology

''T. heterophylla'' is an integral component of
Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as 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 ...
forests west of the
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. Although th ...
, where it is a
climax species Climax species, also called late seral, late-successional, K-selected or equilibrium species, are plant species that can germinate and grow with limited resources; e.g., they need heat exposure or low water availability. They are the species wi ...
. It is also an important
timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...
tree throughout the region, along with many of its large coniferous associates. The species is closely associated with
temperate rainforest Temperate rainforests are coniferous or broadleaf forests that occur in the temperate zone and receive heavy rain. Temperate rain forests occur in oceanic moist regions around the world: the Pacific temperate rain forests of North American ...
s, and most of its range is less than from the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
. Valleys it can be found in usually receive at least of rain annually. It mostly grows at low altitudes, from sea level to . In western
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
, it can be found up to elevations of . The species can also be found in humid areas of mountains further inland, where
western white pine Western white pine (''Pinus monticola''), also called silver pine and California mountain pine, is a species of pine in the family Pinaceae. It occurs in mountain ranges of northwestern North America. It is the state tree of Idaho. Description ...
is normally dominant. For example, in the
Columbia Mountains The Columbia Mountains are a group of mountain ranges along the upper Columbia River in British Columbia, Montana, Idaho and Washington. The mountain range covers 135,952 km² (52,491 sq mi). The range is bounded by the Rocky Mountain T ...
in and around southeastern
British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
and
northern Idaho The Idaho Panhandle—locally known as North Idaho—is a salient region of the U.S. state of Idaho encompassing the state's 10 northernmost counties: Benewah, Bonner, Boundary, Clearwater, Idaho, Kootenai, Latah, Lewis, Nez Perce, and Sho ...
, it grows up to , particularly on north-facing slopes. In the interior part of its range in Idaho, it can be found up to . Western hemlock is a very
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 commercial ...
tree; among associated species in the Pacific Northwest, it is matched or exceeded in shade tolerance only by Pacific yew and
Pacific silver fir ''Abies amabilis'', commonly known as the Pacific silver fir, is a fir native to the Pacific Northwest of North America, occurring in the Pacific Coast Ranges and the Cascade Range. It is also commonly referred to as the white fir, red fir, lov ...
. Young plants typically grow up under the canopy of other conifers such as
Sitka spruce ''Picea sitchensis'', the Sitka spruce, is a large, coniferous, evergreen tree growing to almost tall, with a trunk diameter at breast height that can exceed 5 m (16 ft). It is by far the largest species of spruce and the fifth-larg ...
or
Douglas-fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three va ...
, where they can persist for decades waiting to exploit a gap in the canopy. They eventually replace these conifers, which are relatively shade-intolerant, in climax forest. However,
storm A storm is any disturbed state of the natural environment or the atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmos ...
s and
wildfire A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
s will create larger openings in the forest where these other species can then regenerate. Its thin bark and shallow roots makes it susceptible to fire. At higher elevations, the species can be found mingling with ''T. mertensiana'' (mountain hemlock), seeming to take on some of its characteristics although there is no hard evidence of hybridization. Western hemlock forms
ectomycorrhiza An ectomycorrhiza (from Greek ἐκτός ', "outside", μύκης ', "fungus", and ῥίζα ', "root"; pl. ectomycorrhizas or ectomycorrhizae, abbreviated EcM) is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobi ...
l associations with some well-known
edible fungi Edible mushrooms are the fleshy and edible fruit bodies of several species of macrofungi (fungi which bear fruiting structures that are large enough to be seen with the naked eye). They can appear either below ground (hypogeous) or above ground ...
such as chanterelles (''
Cantharellus formosus ''Cantharellus formosus'', commonly known as the Pacific golden chanterelle, is a fungus native to the Pacific Northwest region of North America. It is a member of the genus ''Cantharellus'' along with other popular edible chanterelles. It was ...
'', '' C. subalbidus'', and ''
Craterellus tubaeformis ''Craterellus tubaeformis'' (formerly ''Cantharellus tubaeformis'') is an edible fungus, also known as yellowfoot, winter mushroom, or funnel chanterelle. It is mycorrhizal, forming symbiotic associations with plants, making it very challengi ...
''). It is capable of associating with wood-decay fungi in addition to soil fungi; this enables its seedlings to survive on rotting stumps and logs. Older forests are damaged by rot-causing fungi,
dwarf mistletoe The genus ''Arceuthobium'', commonly called dwarf mistletoes, is a genus of 26 species of parasitic plants that parasitize members of Pinaceae and Cupressaceae in North America, Central America, Asia, Europe, and Africa. Of the 42 species tha ...
, and
leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...
-consuming insects such as '' Acleris gloverana'' and ''
Lambdina fiscellaria ''Lambdina fiscellaria'', the mournful thorn or hemlock looper, is a moth of the family Geometridae. It is found in North America, from the Pacific to the Atlantic coast and from Canada south to Pennsylvania, Wisconsin and California. The adult ...
''.


Uses

The bark has long served as a source of
tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...
for tanning leather.


Cultivation

Western hemlock is cultivated as an
ornamental tree Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that i ...
in
garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate both ...
s in its native habitats and along the U.S. Pacific Coast, where its best reliability is seen in wetter regions. In relatively dry areas, as at
Victoria, British Columbia Victoria is the capital city of the Canadian province of British Columbia, on the southern tip of Vancouver Island off Canada's Pacific coast. The city has a population of 91,867, and the Greater Victoria area has a population of 397,237. Th ...
, it is exacting about soil conditions. It needs a high level of organic matter (well-rotted wood from an old log or stump is best; animal manures may have too much
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
), in a moist, acidic soil. It is also cultivated in
temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
regions worldwide. It has gained the
Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr (Nort ...
's
Award of Garden Merit The Award of Garden Merit (AGM) is a long-established annual award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. History The Award of Garden Merit ...
. It can also be found in large gardens in northwest Europe and southern New Zealand.


Forestry

When planted on the banks of a river, western hemlock can help reduce erosion. Outside of its natural range, the tree is of importance in
forestry Forestry is the science and craft of creating, managing, planting, using, conserving and repairing forests, woodlands, and associated resources for human and environmental benefits. Forestry is practiced in plantations and natural stands. Th ...
. Until the early 1920s, the tree was largely ignored for use as lumber due to its presumed similarity to the poor-quality
eastern hemlock ''Tsuga canadensis'', also known as eastern hemlock, eastern hemlock-spruce, or Canadian hemlock, and in the French-speaking regions of Canada as ''pruche du Canada'', is a coniferous tree native to eastern North America. It is the state tree of ...
. Since then, it has been greatly utilized for timber (as a
softwood file:Pinus sylvestris wood ray section 1 beentree.jpg, Scots Pine, a typical and well-known softwood Softwood is wood from gymnosperm trees such as conifers. The term is opposed to hardwood, which is the wood from angiosperm trees. The main diff ...
) and
paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distributed ...
production; it is used for making doors, joinery, and furniture. Its fiber is used to make
rayon Rayon is a semi-synthetic fiber, made from natural sources of regenerated cellulose, such as wood and related agricultural products. It has the same molecular structure as cellulose. It is also called viscose. Many types and grades of viscose f ...
and various plastics. It has
naturalised Naturalization (or naturalisation) is the legal act or process by which a non-citizen of a country may acquire citizenship or nationality of that country. It may be done automatically by a statute, i.e., without any effort on the part of the i ...
in some parts of Great Britain and New Zealand—not so extensively as to be considered an
invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
, but as an introduced one.


Food and medicine

The edible
cambium A cambium (plural cambia or cambiums), in plants, is a tissue layer that provides partially undifferentiated cells for plant growth. It is found in the area between xylem and phloem. A cambium can also be defined as a cellular plant tissue from w ...
can be collected by scraping slabs of removed bark. The resulting shavings can be eaten immediately, or can be dried and pressed into bread, as was done by the natives of
Southeast Alaska Southeast Alaska, colloquially referred to as the Alaska(n) Panhandle, is the southeastern portion of the U.S. state of Alaska, bordered to the east and north by the northern half of the Canadian province of British Columbia (and a small part ...
. The inner bark was eaten by some Native American tribes as an emergency food, and the bark was cooked to make medicinal extracts for
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...
,
rheumatic fever Rheumatic fever (RF) is an inflammatory disease that can involve the heart, joints, skin, and brain. The disease typically develops two to four weeks after a streptococcal throat infection. Signs and symptoms include fever, multiple painful jo ...
, and
hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...
. The bark could also be boiled to make dark red dyes to make fishing nets and lines less visible to fish. Western hemlocks have been submerged to collect
herring Herring are forage fish, mostly belonging to the family of Clupeidae. Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...
eggs during the spring spawn in southeast Alaska. The boughs provide an easily collectible surface for the eggs to attach to as well as providing a distinctive taste. This practice originates from traditional gathering methods used by Native Alaskans from southeast Alaska, specifically the
Tlingit people The Tlingit ( or ; also spelled Tlinkit) are indigenous peoples of the Pacific Northwest Coast of North America. Their language is the Tlingit language (natively , pronounced ),
. Tender new-growth needles can be chewed directly or made into a bitter tea, rich in
vitamin C Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) an ...
(similar to some other hemlock and pine species).


Culture

Western hemlock is the
state tree This is a list of U.S. state, federal district, and territory trees, including official trees of the following of the states, of the federal district, and of the territories. Table See also * List of U.S. state, district, and territorial insign ...
of Washington.


References

{{Authority control Pacific temperate rainforests heterophylla Trees of the Northwestern United States Trees of the West Coast of the United States Flora of the Cascade Range Trees of Alaska Trees of British Columbia Trees of the Southwestern United States Trees of mild maritime climate Least concern plants Garden plants of North America Ornamental trees Trees of Subarctic America Trees of Western Canada