Taxus
Encyclopedia
Taxus is a genus
of yews, small coniferous
tree
s or shrub
s in the yew family Taxaceae
. They are relatively slow-growing and can be very long-lived, and reach heights of 1-40 m, with trunk diameters of up to 4 m. They have reddish bark
, lanceolate, flat, dark-green leaves
1-4 cm long and 2-3 mm 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.
The seed cones
are highly modified, each cone containing a single seed
4-7 mm long partly surrounded by a modified scale which develops into a soft, bright red berry
-like structure called an aril
, 8-15 mm long and wide and open at the end. The arils are mature 6-9 months after pollination, and with the seed contained are eaten by thrushes
, waxwing
s and other bird
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, 3-6 mm diameter, and shed their pollen
in early spring. Yews are mostly dioecious
, but occasional individuals can be variably monoecious
, or change sex with time.
All of the yews are very closely related to each other, and some botanists treat them all as subspecies or varieties of just one widespread species; under this treatment, the species name used is Taxus baccata, the first yew described scientifically.
The most distinct is the Sumatran Yew (T. sumatrana, native to Sumatra
and Celebes
north to southernmost China
), distinguished by its sparse, sickle-shaped yellow-green leaves. The Mexican Yew (T. globosa, native to eastern Mexico
south to Honduras
) is also relatively distinct with foliage intermediate between Sumatran Yew and the other species. The Florida Yew, Mexican Yew and Pacific Yew are all rare species listed as threatened or endangered.
All species of yew contain highly poison
ous alkaloid
s known as taxane
s, with some variation in the exact formula of the alkaloid between the species. All parts of the tree except the aril
s contain the alkaloid. The arils are edible and sweet, but the seed is dangerously poison
ous; unlike birds, the human
stomach can break down the seed coat and release the taxanes into the body. This can have fatal results if yew 'berries' are eaten without removing the seeds first. Grazing animals, particularly cattle
and horse
s, are also sometimes found dead near yew trees after eating the leaves, though deer
are able to break down the poisons and will eat yew foliage freely. In the wild, deer browsing of yews is often so extensive that wild yew trees are commonly restricted to cliffs and other steep slopes inaccessible to deer. The foliage is also eaten by the larva
e of some Lepidoptera
n insect
s including Willow Beauty
.
is reddish brown (with whiter sapwood), and is very springy. It was traditionally used to make bows
, especially the longbow
. Ötzi, the Chalcolithic mummy
found in 1991 in the Italian alps, carried an unfinished longbow made of yew wood. Consequently, it is not surprising that, in Norse mythology
, the god of the bow, Ullr
's abode had the name Ydalir
(Yew dales). Most longbow wood used in northern Europe was imported from Iberia
, where climatic conditions are better for growing the knot-free yew wood required. The yew longbow was the critical weapon used by the English in the defeat of the French cavalry
at the Battle of Agincourt
, 1415. It is suggested that English parish
es were required to grow yews and, because of the trees' toxic properties, they were grown in the only commonly enclosed area of a village - the churchyard.
The Eihwaz
rune ᛇ is named after the yew, and sometimes also associated with the "evergreen" World tree
, Yggdrasil
.
Yews are widely used in landscaping and ornamental horticulture
. Over 400 cultivar
s of yews have been named, the vast majority of these being derived from Taxus baccata (European Yew) or Taxus cuspidata (Japanese Yew). The hybrid between these two species is (Taxus x media). A popular fastigiate selection of the European Yew (Taxus baccata 'Fastigiata') is often called the Irish Yew, which often complements the fact of the difficulties with common names. A few cultivars with yellow leaves that are being propagated, collectively are known as golden yews, which is another nomenclature blunder.
The Pacific Yew Taxus brevifolia, native to the Pacific Northwest
of North America
, and Canada Yew Taxus canadensis are the sources of paclitaxel
or Taxol, a chemotherapeutic
drug used in breast
and lung cancer
treatment and, more recently, in the production of the Taxus drug eluting stent by Boston Scientific
. Over-harvesting of the Pacific Yew for this drug has resulted in it becoming an endangered species
, though the drug is now produced semi-synthetically from cultivated yews, without the need to further endanger the wild populations. The more common Canada yew, Taxus canadensis, is also being successfully harvested in northern Ontario
, Québec
and New Brunswick
, and has become another major source of paclitaxel. Other yew species contain similar compounds with similar biochemical activity. Docetaxel, an analogue of paclitaxel, is derived from the Taxus baccata.
The yew tree can often be found in church graveyards and is symbolic of sadness. Such a representation appears in Lord Alfred Tennyson's poem "In Memoriam A.H.H.
" (2.61-64).
The yew tree is a frequent symbol in the Christian poetry of T. S. Eliot
, especially his Four Quartets
.
On January 18, 2008, the Botanic Gardens Conservation International
(representing botanic gardens in 120 countries) stated that "400 medicinal plants are at risk of extinction, from over-collection and deforestation, threatening the discovery of future cures for disease." These included Yew tree
s (the bark is used for cancer drugs, paclitaxel
).
Taxus x hunnewelliana = Taxus cuspidata x Taxus canadensis
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of yews, small coniferous
Pinophyta
The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...
tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s or shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
s in the yew family Taxaceae
Taxaceae
The family Taxaceae, commonly called the yew family, includes three genera and about 7 to 12 species of coniferous plants, or in other interpretations , six genera and about 30 species....
. They are relatively slow-growing and can be very long-lived, and reach heights of 1-40 m, with trunk diameters of up to 4 m. They have reddish bark
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
, lanceolate, flat, dark-green leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
1-4 cm long and 2-3 mm 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.
Conifer cone
A cone is an organ on plants in the division Pinophyta that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity...
are highly modified, each cone containing a single seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
4-7 mm long partly surrounded by a modified scale which develops into a soft, bright red berry
Berry
The botanical definition of a berry is a fleshy fruit produced from a single ovary. Grapes are an example. The berry is the most common type of fleshy fruit in which the entire ovary wall ripens into an edible pericarp. They may have one or more carpels with a thin covering and fleshy interiors....
-like structure called an aril
Aril
An aril is any specialized outgrowth from the funiculus that covers or is attached to the seed. It is sometimes applied to any appendage or thickening of the seed coat in flowering plants, such as the edible parts of the mangosteen and pomegranate fruit, the mace of the nutmeg seed, or the...
, 8-15 mm long and wide and open at the end. The arils are mature 6-9 months after pollination, and with the seed contained are eaten by thrushes
Thrush (bird)
The thrushes, family Turdidae, are a group of passerine birds that occur worldwide.-Characteristics:Thrushes are plump, soft-plumaged, small to medium-sized birds, inhabiting wooded areas, and often feed on the ground or eat small fruit. The smallest thrush may be the Forest Rock-thrush, at and...
, waxwing
Waxwing
The waxwings form the genus Bombycilla of passerine birds. According to most authorities, this is the only genus placed in the family Bombycillidae.-Description:Waxwings are characterised by soft silky plumage...
s and other bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
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, 3-6 mm diameter, and shed their pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
in early spring. Yews are mostly dioecious
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
, but occasional individuals can be variably monoecious
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
, or change sex with time.
All of the yews are very closely related to each other, and some botanists treat them all as subspecies or varieties of just one widespread species; under this treatment, the species name used is Taxus baccata, the first yew described scientifically.
The most distinct is the Sumatran Yew (T. sumatrana, native to Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
and Celebes
Sulawesi
Sulawesi is one of the four larger Sunda Islands of Indonesia and is situated between Borneo and the Maluku Islands. In Indonesia, only Sumatra, Borneo, and Papua are larger in territory, and only Java and Sumatra have larger Indonesian populations.- Etymology :The Portuguese were the first to...
north to southernmost China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
), distinguished by its sparse, sickle-shaped yellow-green leaves. The Mexican Yew (T. globosa, native to eastern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
south to Honduras
Honduras
Honduras is a republic in Central America. It was previously known as Spanish Honduras to differentiate it from British Honduras, which became the modern-day state of Belize...
) is also relatively distinct with foliage intermediate between Sumatran Yew and the other species. The Florida Yew, Mexican Yew and Pacific Yew are all rare species listed as threatened or endangered.
All species of yew contain highly poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....
ous alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s known as taxane
Taxane
The taxanes are diterpenes produced by the plants of the genus Taxus . As their name suggests, they were first derived from natural sources, but some have been synthesized artificially. Taxanes include paclitaxel and docetaxel . Paclitaxel was originally derived from the Pacific yew tree.Taxanes...
s, with some variation in the exact formula of the alkaloid between the species. All parts of the tree except the aril
Aril
An aril is any specialized outgrowth from the funiculus that covers or is attached to the seed. It is sometimes applied to any appendage or thickening of the seed coat in flowering plants, such as the edible parts of the mangosteen and pomegranate fruit, the mace of the nutmeg seed, or the...
s contain the alkaloid. The arils are edible and sweet, but the seed is dangerously poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....
ous; unlike birds, the human
Human
Humans are the only living species in the Homo genus...
stomach can break down the seed coat and release the taxanes into the body. This can have fatal results if yew 'berries' are eaten without removing the seeds first. Grazing animals, particularly cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
and horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s, are also sometimes found dead near yew trees after eating the leaves, though deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
are able to break down the poisons and will eat yew foliage freely. In the wild, deer browsing of yews is often so extensive that wild yew trees are commonly restricted to cliffs and other steep slopes inaccessible to deer. The foliage is also eaten by the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e of some Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
n insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s including Willow Beauty
Willow Beauty
| image = Peribatodes.rhomboidaria.7197.jpg| image_width = 240px| image_caption = Adult male from Dresden | regnum = Animalia| phylum = Arthropoda| classis = Insecta| ordo = Lepidoptera| zoodivisio = Ditrysia| familia = Geometridae...
.
Uses and traditions
Yew woodWood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
is reddish brown (with whiter sapwood), and is very springy. It was traditionally used to make bows
Bow (weapon)
The bow and arrow is a projectile weapon system that predates recorded history and is common to most cultures.-Description:A bow is a flexible arc that shoots aerodynamic projectiles by means of elastic energy. Essentially, the bow is a form of spring powered by a string or cord...
, especially the longbow
Longbow
A longbow is a type of bow that is tall ; this will allow its user a fairly long draw, at least to the jaw....
. Ötzi, the Chalcolithic mummy
Mummy
A mummy is a body, human or animal, whose skin and organs have been preserved by either intentional or incidental exposure to chemicals, extreme coldness , very low humidity, or lack of air when bodies are submerged in bogs, so that the recovered body will not decay further if kept in cool and dry...
found in 1991 in the Italian alps, carried an unfinished longbow made of yew wood. Consequently, it is not surprising that, in Norse mythology
Norse mythology
Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...
, the god of the bow, Ullr
Ullr
In early Germanic paganism, *Wulþuz appears to have been a major god, or an epithet of an important god, in prehistoric times....
's abode had the name Ydalir
Ydalir
In Norse mythology, Ýdalir is a location containing a dwelling owned by the god Ullr. Ýdalir is solely attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources...
(Yew dales). Most longbow wood used in northern Europe was imported from Iberia
Iberian Peninsula
The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...
, where climatic conditions are better for growing the knot-free yew wood required. The yew longbow was the critical weapon used by the English in the defeat of the French cavalry
Cavalry
Cavalry or horsemen were soldiers or warriors who fought mounted on horseback. Cavalry were historically the third oldest and the most mobile of the combat arms...
at the Battle of Agincourt
Battle of Agincourt
The Battle of Agincourt was a major English victory against a numerically superior French army in the Hundred Years' War. The battle occurred on Friday, 25 October 1415 , near modern-day Azincourt, in northern France...
, 1415. It is suggested that English parish
Parish
A parish is a territorial unit historically under the pastoral care and clerical jurisdiction of one parish priest, who might be assisted in his pastoral duties by a curate or curates - also priests but not the parish priest - from a more or less central parish church with its associated organization...
es were required to grow yews and, because of the trees' toxic properties, they were grown in the only commonly enclosed area of a village - the churchyard.
The Eihwaz
Eihwaz
Eiwaz or Eihaz was a Proto-Germanic word for "yew", and the reconstructed name of the rune ....
rune ᛇ is named after the yew, and sometimes also associated with the "evergreen" World tree
World tree
The world tree is a motif present in several religions and mythologies, particularly Indo-European religions, Siberian religions, and Native American religions. The world tree is represented as a colossal tree which supports the heavens, thereby connecting the heavens, the earth, and, through its...
, Yggdrasil
Yggdrasil
In Norse mythology, Yggdrasil is an immense tree that is central in Norse cosmology. It was said to be the world tree around which the nine worlds existed...
.
Horticulture
Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic...
. Over 400 cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
s of yews have been named, the vast majority of these being derived from Taxus baccata (European Yew) or Taxus cuspidata (Japanese Yew). The hybrid between these two species is (Taxus x media). A popular fastigiate selection of the European Yew (Taxus baccata 'Fastigiata') is often called the Irish Yew, which often complements the fact of the difficulties with common names. A few cultivars with yellow leaves that are being propagated, collectively are known as golden yews, which is another nomenclature blunder.
The Pacific Yew Taxus brevifolia, native to the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, and Canada Yew Taxus canadensis are the sources of paclitaxel
Paclitaxel
Paclitaxel is a mitotic inhibitor used in cancer chemotherapy. It was discovered in a U.S. National Cancer Institute program at the Research Triangle Institute in 1967 when Monroe E. Wall and Mansukh C. Wani isolated it from the bark of the Pacific yew tree, Taxus brevifolia and named it taxol...
or Taxol, a chemotherapeutic
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
drug used in breast
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
and lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
treatment and, more recently, in the production of the Taxus drug eluting stent by Boston Scientific
Boston Scientific
The Boston Scientific Corporation , is a worldwide developer, manufacturer and marketer of medical devices whose products are used in a range of interventional medical specialties, including interventional cardiology, peripheral interventions, neuromodulation, neurovascular intervention,...
. Over-harvesting of the Pacific Yew for this drug has resulted in it becoming an endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
, though the drug is now produced semi-synthetically from cultivated yews, without the need to further endanger the wild populations. The more common Canada yew, Taxus canadensis, is also being successfully harvested in northern Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
, Québec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
and New Brunswick
New Brunswick
New Brunswick is one of Canada's three Maritime provinces and is the only province in the federation that is constitutionally bilingual . The provincial capital is Fredericton and Saint John is the most populous city. Greater Moncton is the largest Census Metropolitan Area...
, and has become another major source of paclitaxel. Other yew species contain similar compounds with similar biochemical activity. Docetaxel, an analogue of paclitaxel, is derived from the Taxus baccata.
The yew tree can often be found in church graveyards and is symbolic of sadness. Such a representation appears in Lord Alfred Tennyson's poem "In Memoriam A.H.H.
In Memoriam A.H.H.
In Memoriam A.H.H. is a poem by the English poet Alfred, Lord Tennyson, completed in 1849. It is a requiem for the poet's Cambridge friend Arthur Henry Hallam, who died suddenly of a cerebral haemorrhage in Vienna in 1833...
" (2.61-64).
The yew tree is a frequent symbol in the Christian poetry of T. S. Eliot
T. S. Eliot
Thomas Stearns "T. S." Eliot OM was a playwright, literary critic, and arguably the most important English-language poet of the 20th century. Although he was born an American he moved to the United Kingdom in 1914 and was naturalised as a British subject in 1927 at age 39.The poem that made his...
, especially his Four Quartets
Four Quartets
Four Quartets is a set of four poems written by T. S. Eliot that were published individually over a six-year period. The first poem, "Burnt Norton", was written and published with a collection of his early works following the production of Eliot's play Murder in the Cathedral...
.
On January 18, 2008, the Botanic Gardens Conservation International
Botanic Gardens Conservation International
Botanic Gardens Conservation International is a plant conservation charity based in London, England. It is a membership organisation, working with 800 botanic gardens in 118 countries, whose combined work forms the world's largest plant conservation network.Founded in 1987, BGCI is a registered...
(representing botanic gardens in 120 countries) stated that "400 medicinal plants are at risk of extinction, from over-collection and deforestation, threatening the discovery of future cures for disease." These included Yew tree
Taxus brevifolia
Taxus brevifolia is a conifer native to the Pacific Northwest of North America. It ranges from southernmost Alaska south to central California, mostly in the Pacific Coast Ranges, but with an isolated disjunct population in southeast British Columbia, most notably occurring on Zuckerberg Island...
s (the bark is used for cancer drugs, paclitaxel
Paclitaxel
Paclitaxel is a mitotic inhibitor used in cancer chemotherapy. It was discovered in a U.S. National Cancer Institute program at the Research Triangle Institute in 1967 when Monroe E. Wall and Mansukh C. Wani isolated it from the bark of the Pacific yew tree, Taxus brevifolia and named it taxol...
).
Hybrids
Taxus x media = Taxus baccata x Taxus cuspidataTaxus x hunnewelliana = Taxus cuspidata x Taxus canadensis