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Eastern Hemlocks

2009-12-11 15:38:37.0

Mary Holland

 

Eastern Hemlock
Eastern Hemlock  

Eastern hemlocks (Tsuga canadensis), aptly named for the part of North America where they can be found, often tower above surrounding trees, like so many church spires reaching into the sky. (Unlike spires, however, the tips of hemlocks are quite flexible and often curved, away from prevailing winds.) This majesty did not come easily or quickly to eastern hemlocks.  Unlike the seeds of most trees, which require sunlight and can grow in soil that at times is somewhat dry, those of the eastern hemlock are extremely light-sensitive and demand not only shade, but fairly moist, yet well-drained, soil in order to germinate.  Only after other trees have produced a shaded forest floor, thereby making it inhospitable for their own sun-loving seeds to develop, does the eastern hemlock move in.  At this point there is very little competition with other species, for few are as shade-loving as the eastern hemlock -- eastern white pine, spruces, red maple, sugar maple, American beech and yellow birch come to mind.  After many years, the hemlocks will have created conditions that eliminate all but the shade-loving American beech, and sometimes even that species. 


The shade-tolerant eastern hemlock grows very slowly, taking as much as 250 to 300 years to mature; there exist records of 800-year-old hemlocks. Eastern hemlocks produce a small, egg-shaped reddish cone, not much bigger than your thumb nail when it reaches maturity.  Cones open in the fall, and their seeds are dispersed throughout the winter.


Eastern hemlock bark contains a large amount of tannin, which Native Americans discovered was useful in treating burns.  In addition, its bark was used for tanning leather, as well as for dyeing wool brown and giving leather a reddish tone.  It is still used today in the making of pulp, among other things.  Chances are the newspapers you read may well have been made from the pulp of eastern hemlocks. 


Wildlife such as white-tailed deer and ruffed grouse benefit from dense hemlock stands in the winter, seeking shelter under their snow-catching branches. Northern flickers, black-capped chickadees, pine siskins, American goldfinches and crossbills all feed on the seeds of eastern hemlock.  Many birds use the cover of Eastern hemlock branches for shelter and it is the preferred nesting site of the American robin, blue jay and wood thrush (DeGraaf and Witman, Trees, Shrubs and Vines for Attracting Birds.)  Unfortunately, the hemlock woolly adelgid, an exotic insect from Asia, is spreading throughout the Northeast, feeding on the sap of eastern hemlocks, usually causing them to die within four years.


Cool, moist and shady – these are the conditions that eastern hemlocks favor.  Look for them where the ground is moist, rocky, and often quite steep – locations such as ravines, rocky ridges and moist, cool mountain slopes.  They also grow near fast-running streams, ponds and swamps.  If you should find yourself camping under the boughs of a hemlock, one word of caution – do not use their branches to start a fire, as their wood throws off sparks and knot holes are so hard they can dull an axe.

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