Hemlock grove at the Flight 93 National Memorial
Hemlock grove at the Flight 93 National Memorial.
Credit: James O’Guinn

Trees stand witness to many significant historical moments, often taking on a symbolism of resilience and hope. The witness trees that stand at the Flight 93 National Memorial are such trees. Managed by the National Park Service, this grove of hemlocks is the spot into which Flight 93 crashed on September 11, 2001, when crew and passengers aboard the aircraft thwarted al-Qaeda hijackers’ attempt to crash the plane into the U.S. Capitol Building.

hemlock woolly adelgid
Hemlock woolly adelgid egg sacs. Credit: Sloan Poe

Now, those trees that stood witness to a tragic occasion and have come to stand in memoriam to the brave crew and passengers of Flight 93 are under siege by an invasive insect. Hemlock woolly adelgid, most easily spotted by its white egg sacs, is currently present in about half of the Eastern hemlock’s range, in states from Georgia to Maine, and could spread further north.

The National Park Service announced last week that they are taking action to try to prevent the further spread of the insect among the witness trees. The project will include several methods of treatment, including soil-buried tablets, soil injection, tree injection, bark spray and horticultural oil spray. Many young seedlings and saplings and 1,351 mature trees will undergo treatment.

Learn more about the witness trees and Flight 93 National Memorial at the National Park Service website. To learn more about hemlock woolly adelgid, read the American Forests magazine feature, “The Last of the Giants,” by Will Blozan.