Canada yew and Western yew Taxus canadensis / Taxus brevifolia

Canada yew and Western yew

The Taxaceae family includes only 8 to 10 species in the boreal forest, three of which are indigenous to North America, and two to Canada: the Western (or Pacific) yew, Taxus brevifolia, and the Canada yew, Taxus canadensis.

The Western yew, as can be seen from its name, is to be found in the west of North America, while the Canada yew is in the east. The western species can grow to a height of 20 metres (65 ft.) whereas the eastern species is a creeping shrub about 2 metres (6 ½ ft.) in height.

Being so small, the Canada yew is less attractive for commercial use than its western cousin, which reaches a respectable height. The latter is used for specialized craft such as paddles, tool handles, bows, and also in sculpture. The name of the genus, Taxus, in fact means “a bow”. In this family, the fruit is different from those of other conifers. The seeds are residually separated and when they come to maturity, the fruit is covered in a fleshy red membrane known as an aril. The fruit is eaten by birds who thus scatter the plant’s seeds. Its needles are said to be eaten by the white-tailed deer and the moose, but both fruit and needles are toxic for horses.

As far as humans are concerned, the main importance of this group lies elsewhere. A compound called paclitaxel, marketed under the commercial name of Taxol, which was discovered round 1960, is used as treatment for cancer. Paclitaxel is extracted from the bark, needles and branchlets of the Western yew. However, extracting the paclitaxel creates enormous pressure on the species because it results in the death of the tree. Since the Western yew population is fairly limited and its growth rate is very slow, it was necessary to find another solution to obtain sufficient quantities of paclitaxel. It is now produced from a precursor which is present in the leaves of other members of the Taxaceae family. Researchers are also working with new plantations so the pressure on the Western yew is greatly lessened.

The role of the Western yew in the fight against cancer demonstrates the importance of maintaining the biodiversity of our ecosystem. Not only does this ensure the survival of other species, it also ensures ours, since we are all interlinked in a very complex and quite fascinating jigsaw puzzle.