|
 |
Science
> Biotechnology
> Ground Hemlock or Eastern Yew
|
Ground hemlock (Taxus canadensis), also known as Canada yew or eastern
yew, is a low-spreading and relatively slow-growing shrub found in
northeastern North American woods. Unlike most other native evergreens,
it is not used for timber or pulp. Therefore, even though it is an
important food source for deer and other wildlife, the biology and
general ecology of ground hemlock have not been extensively studied
...until fairly recently, that is!
Since the 1960s, the U.S. National Cancer Institute (NCI) has maintained
a large study in which plants from all over the world, including hundreds
of native forest plants from all over North America, are sampled in
an effort to find natural compound(s) that could be used in their
fight against cancer. One of the promising substances the NCI found
was paclitaxil (Taxol®). Found in the bark of the Pacific yew tree
(a big west-coast cousin of ground hemlock), this ‘chemical gem' was
proven to be very effective against ovarian cancer as well as other
diseases. However, it was not until some 20 years later that paclitaxil
and some closely related compounds in the family of substances called
‘taxanes' were found to also occur in our eastern yew. Taxol® (and
related taxanes) show promise against more than 20 cancer and non-cancer
diseases.
Eastern yew can be found throughout Atlantic Canada and in much of
Quebec, but often in small isolated pockets. Although yew can comprise
a significant amount of the total ground cover in some areas, seldom
do you find ‘stands' or, perhaps more accurately, ‘carpets' of it.
Except perhaps in PEI, we do not have inventories of ‘growing stock,'
so we have to say that we do not how much yew exists in our forests.
While some work is ongoing to answer this question, detailed information
is lacking.
Ground hemlock typically grows in the understory of mature and semi-mature
forests. It can be found under most canopy types; hardwoods, softwoods,
and mixed woods. The fact that it usually is found under a closed
canopy does not mean that it will not grow in the open – a common
misconception, resulting from the observation that often after a stand
is harvested, the yew needles ‘burn,' or turn brown. In fact, yew
will grow more vigorously in the open than under shade (ground hemlock
makes a NICE hedge!).
Very little has been published on the growth of eastern yew other
than to describe it as a spreading, slow-growing shrub. Although it
is sometimes grown in nurseries as an ornamental, we do not know how
much biomass we can produce on either a nursery or a wild plant. We
also do not know how plants will respond/recover from tipping, especially
severe, improperly done tipping: a 40- to 50-cm ‘tip' often represents
six to ten years of growth!
Based on the sparse information we have, while we can say that ground
hemlock "is out there," we certainly have no indication of an inexhaustible
supply of raw material, nor do we have any reliable estimates of how
much yew can be sustainably harvested. Harvesting ground hemlock has
the potential to become an extremely valuable ‘renewable' natural
resource for Atlantic Canada, but only if it is managed responsibly.
Sustainable harvesting guidelines have been developed jointly between
Canadian Forest Service - Atlantic Forestry Centre and the Prince
Edward Island Department of Agriculture and Forestry. Although some
harvesting is now occurring in our region, we would encourage anyone
interested in participating in this activity to contact us.
For further information please contact:
Dr. Ron Smith
Canadian Forest Service -Atlantic Forestry Centre
PO Box 4000 Box 2000
Fredericton, N.B.
Tel: (506) 452-3533
Fax: (506) 452-3525
Mr. Bill Glen
PEI Dept. Agriculture & Forestry
PO Box 2000
Charlottetown, PEI
C1A 7N8
Tel: (902) 368-4700
Fax: (902) 368-4713
|
|
