Taxus
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Taxus is a genus of yews, small coniferous trees or shrubs 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.[citation needed] 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, waxwings and other birds, 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 poisonous alkaloids known as taxanes, with some variation in the exact formula of the alkaloid between the species. All parts of the tree except the arils contain the alkaloid. The arils are edible and sweet, but the seed is dangerously poisonous; 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 horses, 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 larvae of some Lepidopteran insects including Willow Beauty.
| Standard Cyclopedia of Horticulture |
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Taxus (ancient Latin name of the yew). Taxaceae, formerly named in the Coniferae. Yew. Ornamental woody plants, grown for their dark green foliage and the scarlet berry-like fruits. Evergreen trees or shrubs: lvs. linear, without resin-ducts, pale or yellowish green beneath, usually 2-ranked: fls. usually dioecious, solitary and axillary, rarely terminal, small, appearing in early spring; staminate globose, composed of 4-8 stamens each, with 3-8 anther-cells attached to the peltate connective; pistillate consisting of a single terminal ovule with several bracts at the base: seed a bony nut surrounded or almost inclosed by a fleshy cup-shaped scarlet disk; cotyledons 2.—Six species are known. They are distributed throughout the northern hemisphere and in Amer. south to Mex. They are all very closely allied and have been considered geographical varieties of a single species. The wood is heavy, hard, close-grained, strong, elastic, and of reddish color. It is highly valued for cabinet-making and turning, and before the invention of gunpowder was in great request in England for the manufacture of bows. The foliage is poisonous to horses and cattle, but the berries are not. The yews are evergreen, usually small slow-growing trees or shrubs, with 2-ranked linear dark green leaves, insignificant flowers and showy berry-like red fruits. The best-known species is T. baccata, which is hardy as far north as Rhode Island and northwestern New York, and in some forms as far as Massachusetts, while T. cuspidata and T. canadensis are considerably hardier and thrive as far north as Canada; the other species are little known in cultivation. The yews are very desirable evergreens for park planting; they are densely clothed with dark green foliage and the pistillate plants are particularly beautiful in autumn when loaded with scarlet fruits. They are well suited for hedges and easily trimmed into any desired shape. They were formerly much used for fantastic topiary work. That the typical tree-like, form of the yew is nowadays not much planted is chiefly due to its slow growth, but the numerous mostly shrubby garden forms are popular plants for small gardens. The yews thrive best in a moderately moist sandy loam and endure shade well. Large plants may be successfully transplanted if it is possible to secure a sufficient ball of earth with the roots. Propagation is by seeds, which do not germinate until the second year, and by cuttings taken early in autumn and kept during the winter in a cool greenhouse or frame; the varieties also often by grafting on the type in early spring in the greenhouse, or sometimes by layers. Plants raised from cuttings grow more slowly than grafted ones and cuttings of the type rarely grow into trees but usually into low-spreading shrubs. T. floridana, Chapm. Bushy tree, 25 ft. high or sometimes shrubby: lvs. slender, 3/4 - 1 in. long, dark green. Fla.—T. koraiensis, Hort.-Cephalotaxus Harringtonia var. fastigiata. —T. Wallichiana, Zucc. Tree, to 100ft.: lvs. gradually long-acuminate, 1-1 1/2 in. long. Himalayas, Malay Archipelago, Philippine Isls. Apparently not in cult.
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Cultivation
Propagation
Pests and diseases
Species
Taxus baccata - European Yew
Taxus brevifolia - Pacific Yew, Western Yew
Taxus canadensis - Canadian Yew
Taxus chinensis (syn. Taxus wallichiana var. chinensis) - Chinese Yew
Taxus cuspidata - Japanese Yew
Taxus floridana - Florida Yew
Taxus globosa - Mexican Yew
Taxus sumatrana - Sumatran Yew
Taxus wallichiana - Himalayan Yew
Hybrids:
- Taxus x media = Taxus baccata x Taxus cuspidata
- Taxus x hunnewelliana = Taxus cuspidata x Taxus canadensis
Gallery
Male cones of Taxus baccata
photo 1
photo 2
photo 3
References
