Ask A Ranger: Hemlocks at Hanging Rock State Park with Ranger Mary

Click the player above to listen to the episode. Read on below for additional references to what Ranger Mary discusses on the episode.

Types of hemlock

Eastern hemlock, Tsuga canadensis
Stone Mountain State Park, J. Mickey

Carolina hemlock, Tsuga caroliniana
Hanging Rock State Park, D. Cook

Hemlock range

Note that one of the overlaps on the maps is the same small dot on the north-central part of North Carolina. This dot is Hanging Rock State Park.

Hanging Rock is separate from the Blue Ridge Mountains but manages to sustain these two mountain species. Carolina hemlocks tend to grow on dry slopes and rocky ridges and slopes. Eastern hemlocks are usually found in moist, cool valleys, as well as rock outcrops and bluffs. Hanging Rock has plenty of rocky outcrops and moist valleys, which leads to our population of both species.

Eastern hemlock range
Photo courtesy of the U.S. Geological Survey

Carolina hemlock range
Photo courtesy of the U.S. Geological Survey

Invasive species: hemlock woolly adelgid

Note where the adelgids get the "woolly" description in their name. The egg sacs contain anywhere from 50 to 300 eggs, which leads to exponential growth when a population of adelgids is established. The adelgid feeds on sap at the base of the tree's needles, which disrupts the nutrient flow within the hemlock. Needles then fall off and the hemlock slowly starves to death. Other opportune insects or disease can kill or further weaken the hemlock trees while under attack from adelgids.

High magnification of the aphid-like body of an adult hemlock woolly adelgid after removal of the wool.
Photo by Michael Montgomery, USDA Forest Service (Source)

Individuals of hemlock woolly adelgid covered with white wool; see crawler emerging indicated by arrow.
Photo courtesy of Pennsylvania Department of Conservation and Natural Resources – Forestry Archive (Source)

Eggs of hemlock woolly adelgid, with the wool pulled aside for viewing.
Photo by Lorraine Graney, Bartlett Tree Experts (Source)

Hemlock woolly adelgid, Adelges tsugae, on hemlock.
Photo by Michael Montgomery, USDA Forest Service (Source)

Hemlock woolly adelgid adult and eggs exposed inside a woolly ovisac.
Photo courtesy of New York Invasive Species Information (Source)

Battling the adelgids: Predator beetles

The predatory beetles that have been released at Hanging Rock include Sasajiscymnus tsugae or the sasi beetle. In addition to chemical treatments, the biological control from these beetles are helping staff protect hemlock trees and ensure their existence for years to come.

Sasi beetle, Sasajiscymnus tsugae
Hanging Rock State Park, M. Griffin

About the Ask a Ranger Podcast

Ranger Crystal and Ranger Jess host the North Carolina State Parks Ask a Ranger Podcast series. Their guest this episode is Ranger Mary Griffin from Hanging Rock State Park.

Email them at askaranger@ncparks.gov.

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