Eastern Hemlock: A Keystone of Pennsylvania’s Forests

Eastern Hemlock: A Keystone of Pennsylvania’s Forests

By LHR Staff, Rowan Crisp

Eastern Hemlocks are Pennsylvania’s State Tree, and for good reason. These evergreens hold a deep cultural, ecological, and historical significance in our forests. Long before European settlers arrived, Indigenous communities lived among vast old-growth stands where hemlock trees towered for hundreds of years. These were the forests early European settlers first encountered in what is now known as Pennsylvania. Dark, cool, cathedral-like groves shaped in part by the hemlock’s dense, shade-casting branches. These forests even inspired Pennsylvania’s name, the root word, sylvan, meaning forest or forested.

Hemlocks have supported people for centuries. Traditionally, their needles and inner bark were used for medicinal teas, pastes, and washes. Later, during the 1800s, the tree became central to one of Pennsylvania’s largest early industries: leather making. At that time, Pennsylvania led the nation not only in lumber production but also in leather production. Tanneries relied heavily on Eastern Hemlock bark for its high tannin content, a crucial element in the hide-tanning process. Beyond bark, hemlock wood was used for construction timber, railroad ties, and sometimes as pulp for papermaking.

During the Civilian Conservation Corps era of the 1930s, hemlock forests were recognized for their role in stabilizing watersheds and protecting cold-water streams, leading to conservation, reforestation, and stream improvement projects across Pennsylvania. Decades earlier, Pennsylvania’s first Commissioner of Forestry, Dr. Joseph Trimble Rothrock, had already stated that the Eastern Hemlock best represented the Commonwealth’s forests. This vision was later realized when the Eastern Hemlock was officially designated Pennsylvania’s State Tree in 1931.

Hemlock forests also support a rich community of plants, fungi, and animals. Although Pennsylvania is known as the Mushroom Capital of the World, it does not currently have an official state fungus. However, a petition is underway to designate the Hemlock Varnish Shelf as the Pennsylvania State Mushroom. As its name suggests, this species thrives on old hemlock trees and carries notable medicinal properties, further highlighting the ecological value of mature hemlock stands.

That’s not the end of Pennsylvania’s State Tree’s connection with other PA State symbols! These trees also help create suitable habitat for fireflies (lightning bugs), Pennsylvania’s State Insect. Even Mountain Laurel, Pennsylvania’s State Flower, is often found growing alongside hemlock in the mixed understory.
From forest ecology to cultural and industrial history, Eastern Hemlocks are truly woven into the story of Pennsylvania. Their presence is significant throughout the seasons, supporting iconic native wildlife. As threats like Hemlock Woolly Adelgid (HWA) continue to challenge this species, understanding their importance becomes even more essential.

Winter is an ideal time for identifying the presence of HWA.
For more information, please visit: https://www.pa.gov/agencies/dcnr/conservation/forests-and-tree/insects-and-diseases/hemlock-woolly-adelgid

Additional Reading:

https://newenglandforestry.org/meet-the-eastern-hemlock/
https://reflectionriding.org/nature-center-news-updates/eastern-hemlock
https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_1/tsuga/canadensis.htm
https://elibrary.dcnr.pa.gov/PDFProvider.ashx?action=PDFStream&docID=1738489
https://libraryexhibits.uvm.edu/omeka/exhibits/show/uvmtrees/eastern-hemlock/what-do-humans-use-it-for-
https://savehemlocksnc.org/hemlocks-hwa/the-importance-of-hemlocks/https://savemihemlocks.org/2025/12/02/winter-is-the-best-time-to-check-trees-for-hemlock-woolly-adelgid/