January 2024 - Eastern Hemlock

Common Name: Eastern Hemlock, Canadian Hemlock

Botanical Name: Tsuga canadensis

Native Range: Hardy to USDA Zones 3-8. Native to Nova Scotia throughout the Eastern United States to Minnesota and south to the mountains of Alabama and Georgia.

Height: Under landscape conditions, Eastern Hemlocks typically grow 40’-70’ tall.

Spread: Under landscape conditions, Eastern Hemlocks typically have a 25’-35’ spread.

Form: Evergreen conifer. Elegant, fine-textured, soft-needled, gracefully pyramidal.

Growth Rate: Moderately slow growth rate. Once established, will put out 12”-24” of growth. The national champion Eastern Hemlock is 159’ by 45’.

Sun: Hemlock prefers full sun to part shade, however, can tolerate full shade. According to Johnson’s Nursery out of Wisconsin, the Eastern Hemlock can survive with as little as 5% sunlight.

Soil: Hemlock prefers moist well drained soil, however when found in a natural setting, Hemlock are often found growing in rocky, low-fertility soils on the edge of a mountain. 

Leaf Description: Needles are small, flat, green, and pointed. 2 ranked soft to the touch about ½” long, spreading around the stem. Needles are dark side above. On the underside of the leaves are two parallel white stripes. The white stripes are stomata lines. 

Flower Description: Eastern Hemlock bears both male and female flowers. The tree begins to flower at about age fifteen. Male flowers, which appear from April to early June, depending on the locality, appear in light-yellow clusters at the axis of needles from the preceding year. Female flowers are pale green and inconspicuous.

Fruit: Hemlock is a conifer or cone bearing pant. Cones are ovoid, stalked, pendulous at maturity, ½”-1” long, green to brown at maturity, persisting into winter.

Bark Description: Bark is initially gray-brown and smooth then turning scaly; older trees are red-brown with wide ridges and furrows; when cut or broken, purple streaks are obvious. 

Fall Color: Evergreen. Yellowing and the loss of old needles in the fall is normal for pine, spruce, arborvitae, hemlock and most evergreen conifers. Most conifers shed older needles each year starting in late August and continuing through November. 

Wildlife Benefit: The hemlock's shallow root system excels along riparian corridors, where the soil remains moist throughout the year. These shade-tolerant trees form dense canopies that provide cool refuge for fish and other wildlife. Eastern Hemlock provides valuable wildlife food and winter shelter. Many species of wildlife benefit from the excellent habitat that a dense stand of hemlock provides. The dense, low branches of young trees provide winter cover for ruffed grouse, wild turkey, and other wildlife. Eastern Hemlock also provides a food source for a number of bird species. White-winged crossbills, northern flickers, black-capped chickadees, boreal chickadees, dark-eyed juncos, red crossbills, American goldfinch, evening grosbeaks, and pine siskins are said to feed on the small, winged seeds from Eastern Hemlock cones.

Tolerates:

• Shade

• Poor soil conditions.

• Does not tolerate excessive drought.

• Does not tolerate pollution.

Possible Disease and Insect Problems: Unfortunately, many old growt hemlock trees have been killed by the hemlock wooly adelgid. Hemlocks are also susceptible to leaf blight, spider mites, hemlock scale, and bagworm.

Uses: Once used as evergreen screenings, groupings, specimen trees, and sheered hedges. Due to the hemlock wooly adelgid, Eastern Hemlocks are very rarely grown in east coast nurseries.

Additional Facts:

• Tannin from the bark of eastern hemlock formerly was extracted for use in processing leather. Now synthetic and important products are used.

• Lumber production from eastern hemlock reached its peak between 1890 and 1910. Primary uses were in light framing, sheathing, roofing, subflooring, boxes, crates, and general millwork.

• The cultivar ‘Traveler’, is a cross between the Chinese hemlock (Tsuga chinensis) and the native Carolina hemlock (Tsuga caroliniana). Traveler has the ability to survive an attack from the hemlock woolly adelgid.

• Pendula or weeping varieties were once very popular, but due to the adelgid, are very rarely seen in commerce.

• Native American Indians used Eastern Hemlock for basket-weaving, tanning, items for children, and wool coloring.

• Pine needle tea, which contains vitamin C, can be made from the Hemlock Tree. This tea was made by the Iroquois Indians for centuries.

• The Eastern Hemlock is the state tree of Pennsylvania.

• The name “hemlock” is believed to come from the smell of the leaves which is reminiscent of the smell of European poison hemlock.

• USDA recommends planting Norway Spruce in places where Hemlocks were lost.

• Hemlocks can be treated with a systemic insecticide and a horticultural oil to reduce adelgid populations. Where to be found on municipal property: There is a weeping hemlock in Marquand Park adjacent to the Ginkgo tree. There are also mature hemlocks in the old growth area of Marquand Park. The Municipality treats the hemlock in Marquand Park with a horticultural oil to reduce adelgid populations. Multiple mature hemlock can also be found in Harrison Street Park off Aiken Avenue.

Where to be found on municipal property: There is a weeping hemlock in Marquand Park adjacent to the Ginkgo tree. There are also mature hemlocks in the old growth area of Marquand Park. The Municipality treats the hemlock in Marquand Park with a horticultural oil to reduce adelgid populations. Multiple mature hemlock can also be found in Harrison Street Park off Aiken Avenue.

References

https://landscapeplants.oregonstate.edu/plants/tsuga-canadensis

https://mortonarb.org/plant-and-protect/trees-and-plants/eastern-hemlock/

https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_1/tsuga/canadensis.htm

https://www.wildflower.org/plants/result.php?id_plant=tsca

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