Hemlock Trees

Hemlocks are a valuable resource in New York State for many reasons, and conserving hemlock trees is vastly important for ecosystem health and for the many benefits they provide to humans and wildlife. Here’s what makes hemlocks so special:

What are eastern hemlocks and why are they important?

The eastern hemlock (Tsuga canadensis) is a foundation species in the areas of the Northeast forest where it is found.  It provides vital ecosystem services that benefit humans and wildlife.  If it is removed from the landscape, the effects can be devastating to other species and costly to remediate.

Appearance

The eastern hemlock is a slow-growing coniferous tree with an attractive, lacy crown that can reach up to 175 feet tall. Hemlocks have small, flat needles that are deep green on the top and pale on the bottom. In the spring, hemlock twigs have bright, almost lime green tips indicating new growth. The bark is roughly textured and can have a reddish hue to it. Hemlocks can live up to 900 years!

Habitat

Hemlock trees prefer cool, moist sites and are often found along streams, lakes, and on steep, north-facing slopes. The roots of hemlock trees often hold soil in place, preventing erosion and runoff from agricultural lands from getting into streams, preserving high water quality in many areas.

Ecology

Hemlocks fulfill a variety of essential ecosystem roles, making them a necessary component of a healthy landscape.  They provide food and shelter for wildlife across the landscape, and they protect and filter water sources that are valuable to animals and humans alike.

Deer, moose, porcupine, grouse, squirrel, and mice all eat hemlock, especially during the winter when other food sources may be scarce.  Hemlock groves also provide excellent sources of cover because of they have a dense canopy and open understory.

The cool shade created by the overhead canopy provides a sanctuary during the hot summer months and keeps snow from melting rapidly during spring thaw, creating a slow steady influx of water into streams and lakes.  Hemlock shade directly over streams is also important for maintaining the temperatures necessary for many aquatic species, including native brook trout.

Hemlocks make up much of the forest cover along shorelines and streams, and are key for preventing erosion and filtering out pollutants.  New York City and other cities in the state rely on the hemlocks surrounding reservoirs and lakes to keep municipal water supplies clean.

How can I identify hemlock trees?

Not sure you can identify an eastern hemlock?  The Arbor Day Foundation’s What tree is that? can help with some easy guided questions.  The Brandeis Conifer Field Guide allows you to view selected species side-by-side as you learn to differentiate them.  For auditory learners, Cornell’s ForestConnect has a great dendrology crash-course video to help you identify and understand the ecology of Northeast conifers.

You may also use our hemlock and HWA identification guide. Download and print to take it along on your next hike!

Hemlock trees and hemlock woolly adelgid

Hemlock trees in New York and throughout the East Coast are threatened by the invasive pest hemlock woolly adelgid. You can learn more about hemlock woolly adelgid on our HWA: Basics page.