Comox Valley Naturalists Society
Knowing Nature . . .
A Tree Yew Should Know
November 17 , 2006
The western yew is a tree you could walk right by and never notice. Some would say it has a scruffy appearance, with spindly, drooping branches spreading haphazardly from its trunk. It is a small tree, hidden in the deep shade beneath towering firs, hemlocks and cedars. Though common, yews are scattered singly through the forest and never found in large stands. For this reason, trying to find a yew tree is like a forest treasure hunt.
Yews are evergreen conifers, and can be identified by two rows sharp-tipped needles that grow in a flattened arrangement along the stem. The outer bark is thin and scaly, while the inner bark is reddish in colour. The trunk is twisted and often somewhat fluted. The yew tree is unusual in that it does not produce a seed cone like most conifers. Yews have separate male and female trees. Male trees produce small pollen cones and female trees produce fleshy red arils encasing hard seeds. Birds and small rodents love the sweet arils, and disperse the seeds through their droppings. Arils are about the size of huckleberry, but should not be confused with the latter, since they are very toxic to humans.
Western yew typically grows to 10 meters in height, and 30 cm in diameter. With lighter conditions, such as the edge of a clearing, yews will sometimes reach a considerable size. The largest western yew on record is 18 meters high and 142 cm in diameter. Yews are very slow growing trees, adapted to living under a canopy of old growth forest.
There are 12 species of yews in the world. The only species native to BC is the western yew, or Pacific yew (Taxus brevifolia). It is found primarily at low elevations along the coast from Alaska south to California. It also occurs in southeastern BC, west of the Rocky Mountains. The European yew, (Taxus baccata) has been used as an ornamental tree in southern BC. It has much denser foliage than the western yew.
In Europe, yews were traditionally revered as a symbol of longevity since some are estimated to be as old as 4,000 years. European yew was valued for making things such as musical instruments and archery bows. The genus for yew, “Taxus”, literally means, “bow”. Many historians believe that Robin Hood’s bow was made from the wood of a yew.
In the Pacific Northwest, foresters historically regarded western yew as a waste tree with no economic value. Despite this, the strong, elastic, decay resistant wood has always been prized by wood carvers. The yellow and red hued wood polishes beautifully, and is considered one of the most attractive locally found woods. First Nations peoples understood the value of this tree. Known to the Haida as “bow plant” and to other groups as “wedge plant”, the wood was made into bows, paddles, wedges, clubs, digging sticks and numerous other implements. Yew was also a sought after trade item.
In recent years, scientists have discovered that the western yew is valuable to medicine. In the 1960’s, the National Cancer Institute initiated a huge plant-screening program. Approximately 35,000 native plants were screened to see if they showed any cancer-fighting properties. Yew bark and other parts of the tree contain taxol, which has been proven to be effective against ovarian cancer, breast cancer, colon cancer and lung cancer. Ongoing research shows that taxol is also effective for non-cancer applications, such as treating arthritis and Alzheimer’s disease.
When taxol became more widely available to the public and demand increased, concerns arose about the consequences of over-harvesting yew trees. Large quantities are of yew are necessary to extract taxol. Today, a synthetic version of taxol has been created, which has allieviated some of the pressures of over harvesting. Taxol remains promising as a treatment for cancer and other diseases.
With the discovery of taxol, the perception of the yew and its value to humanity has changed dramatically. Yew is a powerful example of the unknown value of our forests. It is important to protect native plants and forests by keeping ecosystems intact. We do not know all the mysteries of our native flora, and what future value to medicine some trees and plants may hold.
Click on a link below to view the CVNS newspaper column.