Trees and communication: Not so silent witnesses

Melody Kraus
Adams County Master Gardener

(9/7) As demonstrated by our constant use of modern gadgets with frequent calls and texting, humans love to converse. However, most of our communication with each other is actually non-verbal, varying between 60%-90%, depending on the situation. On a wider scale, human interaction is also non-verbal with our surroundings, including nature. Some of its signs are extremely obvious, such as the color of leaves in the fall, indicating the change of seasons.

However, the plant kingdom, which includes trees, does not just offer displays for people. Its members actually contact each other directly but still non-verbally, with the help of a fungus named, mycorrhizae, which means "fungus root." Having developed a symbiotic relationship with trees, it lives in their roots and grows extremely fine filaments over lengthy distances. They help with the efficient absorption of nutrients and water by serving as root extensions. Furthermore, this network allows trees to communicate, whether or not they are the same species. For example, when attacked by insects, trees send chemicals through the filaments to warn their neighbors, which then activate their own defenses, including producing chemical repellents, as well as attractants, which entice the natural predators of the the attacking insects.

Even after being razed or falling, trees convey information via the science of dendrochronology, the study of tree rings. Counting the number of them can reveal the approximate age. One ring is produced per year in the temperate zones. However, alternating good and bad weather conditions in the same year can cause more than one ring to form. Scientists study the rings in depth to learn about climate conditions and patterns by comparing the results from various specimens in a designated area with each other.

While trees bear witness to their environments, they are also observers and recorders of human events. They are known as witness trees, a phrase that derives from the European practice of marking trees at corners of pieces of land to indicate its boundary lines. Witness trees exist on the Gettysburg Battlefield.

Before the National Park Service was created in 1933, the United States War Department operated Gettysburg National Military Park and surveyed these trees. The agency attached small brass tags and placed lightning "rods" (actually cords) in some. A famous witness tree is the honey locust on Cemetery Hill in the National Soldiers’ Cemetery, which stood at the time of the Gettysburg Address. It appears in the background of the only known picture of Lincoln at the dedication ceremony for the cemetery and probably was 20 years old at that time. Unfortunately, it was badly damaged by lightning in 2008. In 2011, workers for the Gettysburg National Military Park discovered numerous bullets in a fallen oak tree on Culp’s Hill, which they were sawing into pieces. The two sections of the trunk containing the bullets were moved into storage at the military park's museum. Since multiple witness trees remain, living history exists in the town, but their legacy can continue through preservation and additional documentation.

In 2010 (but no longer), Historic Gettysburg, Adams County sold saplings grown from the honey locust tree described above. However, if commemorating literary history or famous Americans is of interest, saplings of a red maple grown from the seeds collected in Henry David Thoreau’s Walden Woods or grown from the acorns of the 200 year old white oak at Rowan Oak, the home of William Faulkner, can be purchased from These descendants can spread the story of their parents to places far away from their original homes and communicate that the past is present.

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