Conifers in peril: Eastern hemlock

Look along steep slopes and gorges along rivers and streams and you will see large stands of evergreen forest. Along with the white pine, a significant amount of these conifers are likely to be the majestic Eastern hemlock.

The Eastern hemlock (Tsuga canadensis) is a tree that thrives in moist climates and is very shade tolerant. The hemlock is very prevalent on the steep slopes of streams and waterways. It is also found near wetlands, and other areas where it can gain a foothold. A stand of hemlocks creates its own microclimate due to shading, and from fallen needles creating a deep duff layer. Many species of wildlife favor a habitat created by a hemlock stand. Red squirrels, for example, forage on the seeds of the hemlock; these small squirrels are synonymous with hemlocks.

There is a threat to the many hemlock stands in the region in the form of a small insect that uses the hemlock tree as a host; the woolly adelgid. The woolly adelgids lay eggs at the base of the needles of a hemlock, which are characterized by the presence of small white balls on the needle bases. When the eggs hatch, the larvae feed on the needles, which cause the needles to die. An infested tree will die in four years or less.

The spread of the woolly adelgid is proving difficult to control, but one measure that can be taken is to avoid transporting firewood, woodchips and other forest products from infested areas to non-infested areas.