Homegrown Habitat, January 2025: Eastern Hemlock
A scraggly Eastern hemlock after a light snowfall in mid January.
Dust of Snow
By Robert Frost
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.
by Sarah Middeleer
Eastern hemlock (Tsuga canadensis) is perhaps the most iconic of the New England conifers. This graceful, elegant tree is incredibly valuable to wildlife, including many birds. Where it has formed large stands, the deeply shaded hemlock forest takes on an other-worldly quality, its floor spongy with years of dropped needles and its air fragrant and cool. Hemlock forests are unique, invaluable ecosystems.
Eastern hemlock is native from eastern Canada south through New England to the mid-Atlantic and parts of Appalachia, and west to Minnesota and South Dakota. It often grows in moist valleys, along stream banks, and on north-facing slopes. This majestic tree can live up to 350 years, although some specimens have lived over 500 years. One hemlock in northwestern Pennsylvania was determined to be 651 years old.
Unfortunately eastern hemlock is severely threatened by an insect pest called hemlock wooly adelgid, imported from Asia in 1924. Adelgid spread through much of the American hemlock range in the late nineties and early 2000s, from Georgia to Maine. According to one author, “The big tree story for this species is one of death and decline,” describing how the largest, oldest hemlocks have seemingly all succumbed to this pernicious pest.
Lest you turn away thinking there’s enough bad news these days without having to endure it even in “Homegrown Habitat,” the same author explains that new efforts, using predatory beetles (known as biocontrol), have shown good results – and that “the prospects for saving eastern hemlock are now quite good.”
Black-capped Chickadee by Brian Bennett
Do you have hemlocks?
If so, which birds have you seen in them? Send questions and comments to homegrown@ctaudubon.org. Readers’ photos are welcome!
While hemlocks can be seen at several Connecticut Audubon sanctuaries, notable stands of old-growth hemlocks are at Bafflin Sanctuary in Pomfret and at Pratt Preserve in New Milford.
Hemlocks line one side of my driveway, having been here when we moved in almost 25 years ago. They too became infested with woolly adelgid but have remained relatively healthy with occasional treatments of dormant oil. Last year I ordered a type of predatory beetle called ST (Sasajiscymnus tsugae) and released them on the trees. This spring I’ll be eager to see how effective they’ve been.
Hemlock is a keystone species, meaning that it has tremendous ecological value. Its network of fibrous roots help to control erosion, and its dense canopy cools the air. The shade from streamside hemlocks is vital to the habitat for trout and other aquatic wildlife. Hemlock also provides nesting sites, food, and shelter to over 96 species of birds, including migratory songbirds, woodpeckers, and raptors. Over 47 species of mammals also depend on this tree. Porcupines have been known to chew off the top-most branches, some of which then fall to the ground where waiting deer will eat them.
The seeds within hemlock cones attract numerous songbirds, including Black-Throated Green Warbler, Acadian Flycatcher, Hermit Thrush, Black-Capped Chickadee, Pine Siskin, American Goldfinch, and grosbeaks, crossbills, and finches. Many other birds, including woodpeckers, feast on the plethora of insects attracted to hemlocks (alas, they don’t seem to go for woolly adelgid). These trees also provide cavity nesting sites and are considered one of the best wildlife shelter trees.
I can view some of my hemlocks from the window over my kitchen sink and love to watch the avian activity in their branches. Many a dish goes unwashed when I abandon it to get my binoculars.
Eastern hemlock generally grows slowly to a height of 40 to 70 feet and a breadth of 25 to 35 feet. Very old forest specimens have reached heights of 160 feet but, needless to say, the home gardener need not fear this eventuality in your lifetime.
Hemlock can sustain pruning and is sometimes used for tall clipped hedges. But the greatest value to wildlife is to minimize pruning in favor of cone production. Pollination by wind occurs in late winter to early spring. The resulting tiny cones, dangling daintily from twig tips, mature in about six months.
Hemlock needs moist, well-drained, acidic soil and can grow in full sun to shade. It is not drought tolerant. It can be used as a specimen tree or planted in groups for screening. If you have the space, a mass planting will be most beneficial to birds and other wildlife. But even just two or three hemlocks, perhaps under-planted with pagoda dogwood, mapleleaf viburnum, wood ferns, and violets, will be very inviting to birds as well as their human friends.
Do you have hemlocks? If so, which birds have you seen in them? Send questions and comments to homegrown@ctaudubon.org. Readers’ photos are welcome!
While hemlocks can be seen at several Connecticut Audubon sanctuaries, notable stands of old-growth hemlocks are at Bafflin Sanctuary in Pomfret and at Pratt Preserve in New Milford.
“Dust of Snow” from New Hampshire: A Poem with Notes and Grace Notes, by Robert Frost, New York: Henry Holt and Co., 1923.
Resources
Tsuga canadensis (eastern hemlock) description
Level Up Your Winter Birding By Knowing Your Conifers | Audubon
Grow These Native Plants So Your Backyard Birds Can Feast | Audubon
Eastern Hemlock: Needles, Bark, Cones & Facts (With Pictures) – Identification – AMERICAN GARDENER
Dust of Snow | The Poetry Foundation
