Eastern hemlock (Tsuga canadensis) is a beautiful conifer tree with short, dark-green needles, and dark, furrowed bark. It can be found throughout the Credit River watershed in cool, moist sites. It’s a very slow-growing tree capable of living for up to 600 years!
As part of our Natural Areas Inventory program, our biologists document the location and size of large and potentially old eastern hemlocks. The largest eastern hemlock encountered was found in the Georgetown area. It has a diameter at chest height of exactly 100 cm. The tree is growing along what was once a fence-line and scarring from the fence is visible on the trunk.
Forests with large-diameter hemlocks are sporadically found throughout the watershed. Often the hemlocks will be growing with sugar maple (Acer saccharum), American beech (Fagus grandifolia), yellow birch (Betula alleghaniensis), and sometimes eastern white pine (Pinus strobus).
Many large, old hemlocks escaped logging by early settlers in the 1800s in favour of more desirable lumber and fuel wood tree species, although some were harvested for their bark which was used in the tanning industry. The large old hemlocks that remain are relics of the past.
A threat to eastern hemlock, the hemlock woolly adelgid (Adelges tsugae) is established in the eastern United States. This invasive insect is native to Asia and kills trees. Older trees are more susceptible. This pest has not been established in Ontario, but between 2012-2014 isolated populations were found in Etobicoke and Niagara. Both populations were eradicated. You can help by not moving wood or live seedlings which may harbour destructive insects.
The information on hemlock distribution and sizes that we gather is one way we identify and document significant parts of our natural heritage. This information may become more valuable in the future if the hemlock woolly adelgid establishes itself in Ontario.
Visit our conservation areas and try to identify some trees that call the Credit River watershed home.