A yew is a coniferous tree. The name is mainly used for species of the genus Taxus, and sometimes for other conifers in the family Taxaceae.
|Taxus baccata (European yew) shoot with |
mature and immature cones
All species of yew contain highly poisonous alkaloids known as taxanes. All parts of the tree except the arils (red 'fruits') contain the alkaloid.
The arils are edible and sweet, but the seeds are dangerously poisonous. Unlike birds, the human stomach can break down the seed coat and release the taxanes into the body. It can have fatal results if yew 'berries' are eaten without removing the seeds first.
The seeds and leaves will kill cattle and horses, but deer can break down the poisons and will eat yew foliage freely. Deer browsing of yews is often so extensive that wild yew trees are restricted to cliffs and steep slopes the deer cannot get to. The foliage is also eaten by the larvae of some Lepidopteran insects including the willow beauty moth.
Yews are 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, spear-shaped 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 tree is dioecious: the sexes are on separate trees. 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 are eaten by thrushes, waxwings and other birds, which disperse the hard seeds undamaged in their droppings.
The male cones are round, 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 the yews are very closely related to each other, and often described together as Taxus baccata. They are Gymnosperms in the Pinophyta. They appear in the early Cretaceous period.
Yew wood is reddish brown (with whiter sapwood), and is very springy. It was traditionally used to make bows, especially the longbow.