November’s Native Maryland Plant
Tsuga canadensis
(SOO-guh ka-na-DEN-sis)
Common Name: Eastern Hemlock
It’s November and soon most of the trees in our yards will be bare – their leaves blanketing the ground, providing precious habitat while they improve the soil and prevent erosion. It’s this time of year when the evergreens in our landscapes can become prized possessions. In my yard, the Tsuga canadensis (eastern hemlock) is one such tree. It’s a needled evergreen tree in the Pinaceae (Pine) family, its feathery foliage is much softer than that of most conifers, and its dense, drooping branches are flexible and reach to the ground, making it an excellent border tree in a yard that has something to hide – in my case a fence. In Maryland, eastern hemlock is found most naturally growing in the mountain or piedmont regions, frequently alongside eastern white pine (Pinus strobus) and American beech (Fagus grandifolia). It requires good drainage, acidic soil, and consistent moisture; it is not drought-tolerant.
Although I live in the coastal plain, I chose to plant a Tsuga canadensis on a north-facing slope in my yard, selecting the most ‘mountainous’ area I could find, where it’s out of direct sunlight and wind and where it partially hides the fence with my neighbor. I provide it fresh compost in the spring and when necessary, additional water. This specimen has tripled in size since I planted it, you could say it’s been thriving – until this year.
Tsuga canadensis is very susceptible to the Hemlock woolly adelgid (HWA), a small invasive insect that is most recognizable by the white ‘woolly’ wax it leaves on the twigs and needles. HWA is threatening hemlock forests across the country and it’s why I never recommend planting hemlocks without providing information on HWA. When I was taking a photo of a Cardinalis cardinalis for the September edition of ‘Latin for Gardeners’, I noticed the white clusters on the plant through my camera lens, and I knew right away it was the HWA. I was a bit disheartened, but I knew I could seek treatment for the plant. I contacted an arborist to properly identify HWA and to provide it with the most appropriate, effective, and immediate treatment. The tree has already shown marked improvement – there are no visible signs of HWA.
Eastern hemlocks are important riparian trees with high wildlife value. If you choose to plant one in your yard you should monitor it so you can take swift action if you recognize HWA. In my yard, Tsuga canadensis is a tree worth saving.
NOTE: The common name "hemlock" was reportedly given because the crushed foliage smells like that of the poisonous herbaceous perennial herb hemlock which are native to Europe. No part of Tsuga canadensis is considered poisonous.
Fun Fact: Eastern Hemlock is the state tree of Pennsylvania.
Alison Milligan – MG/MN 2013
Watershed Steward Class 7/Tree Trooper
Chesapeake Bay Landscape Professional (CBLP)
