Canadian hemlock, Eastern hemlock, Tsuga canadensis

December 30, 2013

The way a crow

Shook down on me

The dust of snow

From a hemlock tree


Has given my heart

A change of mood

And saved some part

Of a day I had rued.

-Robert Frost

Canadian hemlock, or Eastern hemlock, Tsuga canadensis, is native to eastern North America. This shade-loving, evergreen, pyramidal-shaped tree grows from 40-70-feet in height. Its long horizontal branches, at the beginning of the growing season, produce new shoots that tend to droop downwards, often creating a graceful effect. Later in the year, these shoot tips slowly reverse their tangent, leaving the winter tree with a more ascending habit. The leaves are 1/3- 2/3” long, lustrous green above, and characterized by two white bands on the underside. With short-petioles, these leaves are set close together, and normally two-ranked, creating a flat plane along the stem. Inconspicuous, ¼ “-long, light yellow, male flowers produce its pollen, and separate, petite, female flowers, if successfully fertilized, develop into approximately 1”-long seed cones, which look like tiny footballs, hanging ornamentally from the branches.  Found on the scales of these cones, are two tiny, winged seeds, evolutionarily evolved to be dispersed by the wind, well away from the parent tree.

A cosmopolitan explanation of the current binomial Tsuga canadensis, was recounted by Sheila Connor, in her interesting, 1994 book, New England Natives. Connor quotes from Bulletin Number 3 of the Hemlock Arboretum,… “In the beginning of scientific botanical practice the [eastern] hemlock was included with the pines. It was labeled Pinus Canadensis by Linnaeus in 1763. Michaux, the French botanist, in 1796 grouped it with the firs and named it Abies Canadensis, while later scientists included it with the spruces and called it Picea Canadensis. It was the celebrated botanist Stephen Ladislaus Endlicher who, in 1847, used the name Tsuga, which is the Japanese name for the hemlock…Later [in 1855], Elie Abel Carrierre, a famous French botanist, classified all the hemlocks… under the generic name Tsuga. Thus this important…North American conifer bears a Japanese name, given by an Austrian, confirmed by a Frenchman, and now accepted by scientists generally.”

Regardless of the taxonomy, Tsuga canadensisCanadian hemlock, an important member of New England’s forests for at least 8000-years, also played a crucial role in many entrepreneurial fortunes made and lost.  For all who appreciate local history, and/or industrial archeology, it is worth remembering that Tsuga canadensis was extensively harvested, for its bark, during the nineteenth-century heyday of the hide-tanning industry.  During our industrial revolution, mill driven machines, were driven by leather belts. Leather belts that drove many machines, and fortunes, were made more resistant to decomposition, by a tanning process that preferred Canadian hemlock bark, with its high tannin content of 10-12 percent.

Despite untold millions of Canadian hemlock trees harvested, throughout the Hemlock-Northern Hardwoods forests of northeastern United States, it still remains abundant. Recent interest in “old-growth forests in Massachusetts” has revealed, and renewed, conservation interest in Canadian hemlocks. Old growth forests have been variously defined, but most definitions include; a lack of substantial human impact, a wide range of tree sizes, abundance of coarse woody debris, and complex structure, among other characteristics.  Research by Anthony D’Amato identified 28 stands of Old Growth in Massachusetts, all west of the Connecticut River. These sites contained a particularly high frequency of Canadian hemlock. The oldest tree for which an age could be determined was a Canadian hemlock, at least 489 years old [in 2006], found in Mohawk Trail State Forest. This would be the oldest known tree in Massachusetts. In Tionesta, PA, a Canadian hemlock was aged at 555-years in 1991.

Donald Culross Peattie (1898-1964), in his well-known, literary, arboreal encomium, A Natural History of Trees, provides an apt coda for us, “Approaching such a noble tree, you think it dark, almost black, because the needles on the upper side are indeed a lustrous deep blue-green. Yet when you… settle your back into the buttresses of the bole and look up under the boughs, their shade seems silvery, since the underside of each needle, is whitened by two lines. Soon even talk of the tree itself is silenced by it, and you fall to listening. When the wind lifts up the Hemlock’s voice, it is no roaring like the Pine’s, no keening like the Spruce’s. The Hemlock whistles softly to itself. It raises its long, limber boughs and lets them drop again with a sigh, not sorrowful, but letting fall tranquility upon us.”

On your next visit to Mount Auburn, where we grow approximately six-dozen Canadian hemlocks, seek out a few of our finer specimens on Azalea Path, Lawn Avenue, Vesper Avenue, Larch Avenue, Willow Avenue, or Oak Avenue, among other locations.


…There is a port-hole of light at the end of the hemlock tunnel:

birds cross it, flashing their voices at you, and you feel-

from the way they tilt their heads and their throats swell-

the beat of their brief song, another sign that the world is what it is:

a shade tree heavy with households,…

-Eamon Grennan


…And ‘neath the hemlock, whose thick branches bent

Beneath its bright cold burden, and kept dry

A circle, on the earth, of withered leaves,

The partridge found a shelter…

-William Cullen Bryant

The moon above the eastern wood

Shone at its full; the hill-range stood

Transfigured in the silver flood,

Its blown snows flashing cold and keen,

Dead white, save where some sharp ravine

Took shadow, or the somber green

Of hemlocks turned to pitchy black

Against the whiteness at their back.

For such a world and such a night

Most fitting that unwarming light,

Which only seemed where’er it fell

To make the coldness visible.

John Greenleaf Whittier

About the Author: Jim Gorman

Visitor Services Assistant View all posts by Jim Gorman →


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