Eastern Hemlock is a native evergreen with a straight trunk, a conical crown of long slender horizontal, somewhat drooping, branches, and growing 60 to 70 feet feet high. The tree's leader is often slender, curved and drooping.
Bark is gray-brown and smooth when young turning to a cinnamon brown with thick furrowed scaly ridges forming flat plates.
Twigs are slender, yellow-brown to gray-brown in color, with dense fine hair. Buds are tiny.
Leaves: The needles are 3/8 to 3/4 inch long, flat and flexible with rounded tips - NOT stiff and pointed like White Spruce - very short stalks (no more than 1/2 the width of the needle), abruptly narrowed peg-like bases, and appear to be in two rows in a single plane. They are dark green to shiny yellow-green above with 2 narrow white bands below (stomatal bands). Edges may have tiny teeth.
Flowers: The tree is monoecious, that is, male and female flowers are separate. Male flowers are small, round yellow cone shapes near the ends of branches. These male cones have globular pollen packets and are mounted on a short green stalk. The female flowers are small light-green ovoid shapes at the branch tips, forming, after pollination, an ovoid light brown cone, about 3/4 inch long that hang from the branches. These are soft and flexible and have rounded scales with rounded smooth margins and mature in the fall.
Fruit: Seed cones are wind pollinated and mature in August and September. Starting in October seed is dispersed by wind. Seeds are paired with elongated wings. Cone scales are not widely spread at dispersion and close during wet weather. Seed production begins around 15 to 20 years of age. Unlike White Spruce, seed cones occur every year.
Habitat: Eastern Hemlock grows in cool moist acidic soil with partial shade. The species is very shade tolerant and actually requires shade for establishment. It is a dominant species but slow growing and long-lived with a shallow widespread root system that is susceptible to overthrow by wind. Trees as old as 800 years have been located. It regenerated by seed but only in areas not subject to deer browsing. The main pest is the Asian Hemlock woolly adelgid, which can cause tree death after an infestation.
Names: The tongue twisting genus name of the tree, Tsuga, is actually from the Japanese name. The species canadensis, means 'of Canada' where the tree was first typed. The author name for the plant classification (following the (L.) for Linnaeus) ‘Carrière’ is for Élie-Able Carrière (1818-1896), French botanist, authority on conifers, who published Traité Général des Conifères in 1855. Two centuries ago the tree as sometimes called Hemlock Spruce and variously identified as Abies canadensis or Pinus canadensis.
Above: 1st photo - The hemlock Grove at Eloise Butler Wildflower Garden. For a summer view see the photo far below. 2nd photo - Bark turns from smooth on young stems to a cinnamon brown with thick furrowed scaly ridges forming flat plates on older trunks. 3rd photo - The needles have very short stalks and appear to be in two rows in a single plane and have 2 narrow white stomatal bands.
Below: 1st photo - Male flowers are small, round yellow cone shapes, that elongate to open the pollen sacs. 2nd photo - Female flowers start as light green cone shapes that turn into brown cones (3rd photo) after pollination and remain soft and flexible until seeds release in the fall.
Below: 1st photo - The male cones have opened revealing the pollen sacs. 2nd photo - The needles are soft and flexible with rounded tips.
Below: The grove of old Hemlocks at the North end of the Woodland Garden.
Notes: Eastern Hemlock is not indigenous to the Garden. Eloise Butler planted the first ones in Sept. 1911 - plants obtained from the Park Board Nursery, and again on May 28, 1914. On that date she recorded planting 28 Hemlocks and these are probably the oldest southern most remaining stand in the state and this stand contains the largest known Eastern Hemlock in Minneapolis which is now on the Minneapolis Heritage Tree List. Gardener Cary George planted 15 new 2-foot trees in 1989. Eastern Hemlock is found in North America in the eastern 1/3, from Ontario and Minnesota eastward to the coast and into the southern states except for Florida.
Tsuga canadensis is the only species of Tsuga found in Minnesota.
Eloise Butler wrote this in 1914 about her planting of the Hemlocks: "Hemlock has not been listed among Minnesotan plants; but it has sneaked in, contrary to rule, with the idea that it may sometime break across the Wisconsin border. In order that the face of nature may be changed as little as possible in our trained wilderness, only a few specimens each of the state flora not indigenous to the Garden are admitted."
Endangered: Minnesota is at the far western edge of the range with a native population only known from Pine county. There were previous populations in Carlton and St. Louis Counties but those were mostly logged off and most of the remaining trees succumbed to forest fires and the rest died off. The MN DNR states there are only about 50 mature trees remaining in the wild. Only recently has the tree been listed as of "Special Concern" and in August 2013 was advanced to "Endangered" status. The population in the Garden and the younger population at the MN Landscape Arboretum is therefore of special importance.
Uses: The wood of Eastern Hemlock is brittle and full of knots, thus not valuable for anything but rough wood needs. An extract of Hemlock bark was once a commercial source of tannin for the production of leather and that use led to the destruction of many mature stands of the tree. Other than the bark, the remainder was discarded. Tea was said to be made from the leafy twigs.
In his important 3-volume work, The North American Sylva, Francois Michaux adds considerable detail to the above: "Unhappily the properties of its wood are such as to give this species only a secondary importance, notwithstanding its abundant diffusion; it is the least valuable in this respect of all the large resinous trees of North America. But the regret which we should experience to see it occupying so extensively the place of more useful species is forbidden by a property of its bark inestimable to the country where it grows, that of being applicable in tanning.
It is taken from the tree in the month of June, and half the epidermis is shaved off with a plane before it is thrown into the mill. From the District of Maine it is exported to Boston, Providence, etc., and is almost exclusively employed in the tan-yards. Its deep red colour is imparted to the leather, and I have been informed by tanners that it is inferior to Oak bark, but that the two species united are better than either of them alone."(Ref. #26d)
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"