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''Tsuga'' (, from
Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...
(), the name of ''
Tsuga sieboldii ''Tsuga sieboldii'', also called the southern Japanese hemlock, or in Japanese, simply tsuga (栂), is a conifer native to the Japanese islands of Honshū, Kyūshū, Shikoku and Yakushima. In Europe and North America the tree is sometimes used a ...
'') is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
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 ...
s in the subfamily
Abietoideae Abietoideae is a subfamily of the conifer family Pinaceae. The name is from the genus ''Abies'' ( firs), which contains most of the species in the genus. Six genera are currently assigned to this subfamily: ''Abies'', ''Cedrus'', ''Keteleeria'', ...
of
Pinaceae The Pinaceae, or pine family, are conifer trees or shrubs, including many of the well-known conifers of commercial importance such as Cedrus, cedars, firs, Tsuga, hemlocks, larches, pines and spruces. The family is included in the order Pinales, ...
, the pine family. The
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
hemlock is derived from a perceived similarity in the smell of its crushed foliage to that of the unrelated plant
poison hemlock ''Conium maculatum'', colloquially known as hemlock, poison hemlock or wild hemlock, is a highly poisonous biennial herbaceous flowering plant in the carrot family Apiaceae, native to Europe and North Africa. A hardy plant capable of living in ...
. Unlike the latter, ''Tsuga'' species are not poisonous. The genus comprises eight to ten species (depending on the
authority In the fields of sociology and political science, authority is the legitimate power of a person or group over other people. In a civil state, ''authority'' is practiced in ways such a judicial branch or an executive branch of government.''The N ...
), with four species occurring in North America and four to six in eastern Asia.


Description

They are medium-sized to 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 ...
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
s, ranging from tall, with a conical to irregular crown, the latter occurring especially in some of the Asian species. The leading shoots generally droop. The
bark Bark may refer to: * 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) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, ...
is scaly and commonly deeply furrowed, with the colour ranging from grey to brown. The branches stem horizontally from the trunk and are usually arranged in flattened sprays that bend downward towards their tips. Short spur
shoot In botany, a plant shoot consists of any plant stem together with its appendages, leaves and lateral buds, flowering stems, and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spri ...
s, which are present in many
gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, ''Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνό ...
s, are weakly to moderately developed. The young twigs, as well as the distal portions of stem, are flexible and often pendent. The stems are rough due to
pulvini A pulvinus (pl. ''pulvini'') is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. Pulvini are common, for example, in members of the bean family Fabaceae (Leguminosae) and the prayer plant ...
that persist after the
leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
fall. The winter
bud In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be spec ...
s are ovoid or globose, usually rounded at the apex and not resinous. The leaves are flattened to slightly angular and range from long and broad. They are borne singly and are arranged spirally on the stem; the leaf bases are twisted so the leaves lie flat either side of the stem or more rarely radially. Towards the base, the leaves narrow abruptly to a petiole set on a forward-angled pulvinus. The petiole is twisted at the base so it is almost parallel with the stem. The leaf apex is either notched, rounded, or acute. The undersides have two white
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 ...
tal bands (which are inconspicuous on '' T. mertensiana'') separated by an elevated midvein. The upper surface of the leaves lack stomata, except those of ''T. mertensiana''. They have one resin canal that is present beneath the single vascular bundle. The
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
cones grow solitary from lateral buds. They are usually up to in length, ovoid, globose, or ellipsoid, and yellowish-white to pale purple, and borne on a short peduncle. The pollen itself has a saccate, ring-like structure at its distal pole, and rarely this structure can be more or less doubly saccate. The
seed cones A conifer cone (in formal botanical usage: strobilus, plural strobili) is a seed-bearing organ on gymnosperm plants. It is usually woody, ovoid to globular, including scales and bracts arranged around a central axis, especially in conifers an ...
are borne on year-old twigs and are small ovoid-globose or oblong-cylindric, ranging from long, except in ''T. mertensiana'', where they are cylindrical and longer, in length; they are solitary, terminal or rarely lateral, pendulous, and are
sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...
or on a short peduncle up to long. Maturation occurs in 5–8 months, and the
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 shed shortly thereafter; the cones are shed soon after seed release or up to a year or two later. The seed scales are thin, leathery, and persistent. They vary in shape and lack an apophysis and an umbo. The
bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...
s are included and small. The seeds are small, from long, and winged, with the wing being in length. They also contain small adaxial resin
vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...
. Seed germination is
epigeal Epigeal, epigean, epigeic and epigeous are biological terms describing an organism's activity above the soil surface. In botany, a seed is described as showing epigeal germination when the cotyledons of the germinating seed expand, throw off the ...
; the seedlings have 4–6
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed." The numb ...
s.


Taxonomy

Mountain hemlock (''T. mertensiana'') is unusual in the genus in several respects. The leaves are less flattened and arranged all round the shoot, and have stomata above as well as below, giving the foliage a glaucous color; and the cones are the longest in the genus, long and cylindrical rather than ovoid. Some botanists treat it in a distinct genus as ''Hesperopeuce mertensiana'' (Bong.) Rydb., though it is more generally only considered distinct at the rank of subgenus. Another species, bristlecone hemlock, first described as ''T. longibracteata'', is now treated in a distinct genus ''
Nothotsuga ''Nothotsuga'' is a genus of coniferous trees in the family Pinaceae endemic to China. ''Nothotsuga'' contains only one species, ''Nothotsuga longibracteata'', commonly known as the bristlecone hemlock, which is found in southeastern China, in ...
''; it differs from ''Tsuga'' in the erect (not pendulous) cones with exserted bracts, and male cones clustered in umbels, in these features more closely allied to the genus ''
Keteleeria ''Keteleeria'' is a genus of three species of coniferous trees in the family Pinaceae first described as a genus in 1866. The genus name ''Keteleeria'' honours J.B. Keteleer (1813–1903), a French nurseryman. The group is related to the genera ...
''.


Species

; Accepted living species * ''
Tsuga canadensis ''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 o ...
'' – eastern hemlock – Eastern Canada, Eastern United States * ''
Tsuga caroliniana ''Tsuga caroliniana'', the Carolina hemlock, is a species of hemlock endemic to the United States. Distribution and habitat Carolina hemlock is native to the Appalachian Mountains in southwest Virginia, western North Carolina, extreme northeas ...
'' – Carolina hemlock – Southern
Appalachians The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
* ''
Tsuga chinensis ''Tsuga chinensis'', commonly referred to as the Taiwan or Chinese hemlock, or in Chinese as tieshan (), is a coniferous tree species native to China, Taiwan, Tibet and Vietnam. The tree is quite variable and has many recognised varieties, thoug ...
'' – Taiwan hemlock – much of China incl Tibet + Taiwan * ''
Tsuga diversifolia ''Tsuga diversifolia'', commonly known as the northern Japanese hemlock, or in Japanese, kometsuga (米栂), is a species of conifer native to the Japanese islands of Honshū, Kyūshū, and Shikoku. In Europe and North America, the species is so ...
'' – northern Japanese hemlock –
Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separ ...
,
Kyushu is the third-largest island of Japan's five main islands and the most southerly of the four largest islands ( i.e. excluding Okinawa). In the past, it has been known as , and . The historical regional name referred to Kyushu and its surroun ...
* ''
Tsuga dumosa ''Tsuga dumosa'', commonly called the Himalayan hemlock or in Chinese, Yunnan tieshan (), is a species of conifer native to the eastern Himalayas. It occurs in parts of Nepal, India, Bhutan, Myanmar, Vietnam and Tibet. Within its native range t ...
'' – Himalayan hemlock –
Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 100 ...
,
Tibet Tibet (; ''Böd''; ) is a region in East Asia, covering much of the Tibetan Plateau and spanning about . It is the traditional homeland of the Tibetan people. Also resident on the plateau are some other ethnic groups such as Monpa people, ...
,
Yunnan Yunnan , () is a landlocked Provinces of China, province in Southwest China, the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is ...
,
Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of the ...
* ''
Tsuga forrestii ''Tsuga forrestii'' is a species of conifer in the family Pinaceae. It is considered as a variety of ''Tsuga chinensis'' (i.e., ''T. c.'' var. ''forrestii'') by some. It grows in mixed forests in mountains and valleys of northeast Guizhou, south ...
'' – Forrest's hemlock –
Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of the ...
,
Yunnan Yunnan , () is a landlocked Provinces of China, province in Southwest China, the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is ...
,
Guizhou Guizhou (; formerly Kweichow) is a landlocked province in the southwest region of the People's Republic of China. Its capital and largest city is Guiyang, in the center of the province. Guizhou borders the autonomous region of Guangxi to t ...
* ''
Tsuga heterophylla ''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, Alaska, and its southeastern limit in northern Sonoma ...
'' – western hemlock – Western Canada, Northwestern United States * ''
Tsuga × jeffreyi ''Tsuga'' (, from Japanese (), the name of ''Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed folia ...
'' –
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, ...
,
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 on ...
* ''
Tsuga mertensiana ''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 ...
'' – mountain hemlock – Alaska,
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, ...
, Western United States * ''
Tsuga sieboldii ''Tsuga sieboldii'', also called the southern Japanese hemlock, or in Japanese, simply tsuga (栂), is a conifer native to the Japanese islands of Honshū, Kyūshū, Shikoku and Yakushima. In Europe and North America the tree is sometimes used a ...
'' – southern Japanese hemlock – Japan * ''
Tsuga ulleungensis ''Tsuga ulleungensis'', also known as the Ulleungdo hemlock, is a conifer species discovered on Ulleungdo island, Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th ...
'' – Ulleungdo hemlock –
Ulleungdo Ulleungdo (also spelled Ulreungdo; Hangul: , ) is a South Korean island 120 km (75 mi) east of the Korean Peninsula in the Sea of Japan, formerly known as the Dagelet Island or Argonaut Island in Europe. Volcanic in origin, the rocky s ...
island, Korea ;Accepted paleospecies * †''
Tsuga aburaensis ''Tsuga'' (, from Japanese (), the name of ''Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed folia ...
'' - Abura, Hokkaido (Miocene) * †''
Tsuga asiatica ''Tsuga'' (, from Japanese (), the name of ''Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliage ...
'' - Lawula Formation,
Tibet Tibet (; ''Böd''; ) is a region in East Asia, covering much of the Tibetan Plateau and spanning about . It is the traditional homeland of the Tibetan people. Also resident on the plateau are some other ethnic groups such as Monpa people, ...
(
Priabonian The Priabonian is, in the ICS's geologic timescale, the latest age or the upper stage of the Eocene Epoch or Series. It spans the time between . The Priabonian is preceded by the Bartonian and is followed by the Rupelian, the lowest stage of t ...
) * †''
Tsuga europaea ''Tsuga'' (, from Japanese (), the name of ''Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliage ...
'' -Maria Theresia mine
Aachen Aachen ( ; ; Aachen dialect: ''Oche'' ; French and traditional English: Aix-la-Chapelle; or ''Aquisgranum''; nl, Aken ; Polish: Akwizgran) is, with around 249,000 inhabitants, the 13th-largest city in North Rhine-Westphalia, and the 28th- ...
(Miocene) * †'' Tsuga nanfengensis'' -
Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...
(Late Miocene) * †''
Tsuga swedaea ''Tsuga'' (, from Japanese (), the name of ''Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliag ...
'' -
Buchanan Lake Formation The Buchanan Lake Formation is a geologic formation on Axel Heiberg Island in Nunavut, and part of the Eureka Sound Group. The formation is divided into four members and preserves fossils dating back to the Lutetian stage. See also * List of ...
,
Axel Heiberg Island Axel Heiberg Island ( iu, ᐅᒥᖕᒪᑦ ᓄᓈᑦ, ) is an uninhabited island in the Qikiqtaaluk Region, Nunavut, Canada. Located in the Arctic Ocean, it is the 32nd largest island in the world and Canada's seventh largest island. According ...
(
Lutetian The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Midd ...
) * †'' Tsuga taxoides'' - Inner Mongolia (Early Cretaceous) * †'' Tsuga xianfengensis'' -
Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...
(late Miocene) ; Formerly included Moved to other genera: ''
Cathaya ''Cathaya'' is a genus in the pine family, Pinaceae, with one known living species, ''Cathaya argyrophylla''. ''Cathaya'' is a member of the subfamily Laricoideae, most closely related to ''Pseudotsuga'' and ''Larix''. A second species, ''C. nan ...
Keteleeria ''Keteleeria'' is a genus of three species of coniferous trees in the family Pinaceae first described as a genus in 1866. The genus name ''Keteleeria'' honours J.B. Keteleer (1813–1903), a French nurseryman. The group is related to the genera ...
Nothotsuga ''Nothotsuga'' is a genus of coniferous trees in the family Pinaceae endemic to China. ''Nothotsuga'' contains only one species, ''Nothotsuga longibracteata'', commonly known as the bristlecone hemlock, which is found in southeastern China, in ...
Picea A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfami ...
Pseudotsuga ''Pseudotsuga'' is a genus of evergreen coniferous trees in the family Pinaceae (subfamily Laricoideae). Common names for species in the genus include Douglas fir, Douglas-fir, Douglas tree, Oregon pine and Bigcone spruce. '' Pseudotsuga menz ...
Taxus ''Taxus'' is a genus of coniferous trees or shrubs known as yews in the family Taxaceae. They are relatively slow-growing and can be very long-lived, and reach heights of , with trunk girth averaging . They have reddish bark, lanceolate, flat, ...
''


Ecology

The species are all adapted to (and are confined to) relatively moist, cool temperate areas with high rainfall, cool summers, and little or no water stress; they are also adapted to cope with heavy to very heavy winter
snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...
fall and tolerate
ice storm An ice storm, also known as a glaze event or a silver storm is a type of winter storm characterized by freezing rain. The U.S. National Weather Service defines an ice storm as a storm which results in the accumulation of at least of ice on ex ...
s better than most other trees. Hemlock trees are more tolerant of heavy shade than other conifers; they are, however, more susceptible to drought.


Threats

The two eastern North American species, '' T. canadensis'' and '' T. caroliniana'', are under serious threat by the sap-sucking
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
''Adelges tsugae'' (
hemlock woolly adelgid The hemlock woolly adelgid (; ''Adelges tsugae''), or HWA, is an insect of the order Hemiptera (true bugs) native to East Asia. It feeds by sucking sap from hemlock and spruce trees (''Tsuga'' spp.; ''Picea'' spp.). In its native range, HWA ...
). This adelgid, related to the
aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s, was introduced accidentally from eastern Asia, where it is only a minor pest. Extensive mortality has occurred, particularly east of the
Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
. The Asian species are resistant to this pest, and the two western American hemlocks are moderately resistant. In North America, hemlocks are also attacked by
hemlock looper ''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 ...
.USDA Forest Service NA-PR-05-92 Larger infected hemlocks have large, relatively high root systems that can bring other trees down if one falls. The foliage of young trees is often browsed by
deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the reindeer ...
, and the seeds are eaten by
finch The true finches are small to medium-sized passerine birds in the family Fringillidae. Finches have stout conical bills adapted for eating seeds and nuts and often have colourful plumage. They occupy a great range of habitats where they are usua ...
es and small
rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s. Old trees are commonly attacked by various
fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
disease and decay species, notably ''
Heterobasidion annosum ''Heterobasidion annosum'' is a basidiomycete fungus in the family Bondarzewiaceae. It is considered to be the most economically important forest pathogen in the Northern Hemisphere. ''Heterobasidion annosum'' is widespread in forests in the Unit ...
'' and ''
Armillaria ''Armillaria'' is a genus of fungi that includes the '' A. mellea'' species known as honey fungi that live on trees and woody shrubs. It includes about 10 species formerly categorized summarily as ''A. mellea''. ''Armillarias'' are long-l ...
'' species, which rot the heartwood and eventually leave the tree liable to
windthrow In forestry, windthrow refers to trees uprooted by wind. Breakage of the tree bole (trunk) instead of uprooting is called windsnap. Blowdown refers to both windthrow and windsnap. Causes Windthrow is common in all forested parts of the w ...
, and ''
Rhizina undulata ''Rhizina undulata'', commonly known as the doughnut fungus or the pine firefungus, is a species of fungus in the family Rhizinaceae. The fruit bodies of the fungus are dark purple brown with a bright yellow margin, crust-like and attached to the ...
'', which may kill groups of trees following minor grass fires that activate growth of the ''Rhizina'' spores.Phillips, D. H., & Burdekin, D. A. (1992). ''Diseases of Forest and Ornamental Trees''. Macmillan .


Uses

The wood obtained from hemlocks is important in the timber industry, especially for use as
wood pulp Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. Mixed with water and other chemical or plant-based additives, pulp is the major raw mate ...
. Many species are used in
horticulture Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...
, and numerous
cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...
s have been selected for use in gardens. The bark of the hemlock is also used in
tanning Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin **Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye t ...
leather. The needles of the hemlock tree are sometimes used to make a tea and perfume.


References


External links

* * {{Authority control Conifer genera