How Can There Be So Many Witness Trees in Gettysburg?

One of the barriers that prevent people from believing that there may be many hundreds of two-century old trees at Gettysburg National Military Park is a scientific one: arboreally speaking, how can there be such a high density of two-century old trees in such a small geographical area, given the amount of development, landscaping and tourism that has burdened battlefield continually since 1863? To put it another way, we are not talking about an untouched virgin forest of tens of thousands of acres, as is found in the redwood and sequoia parks of California.

Well, there are three contributing factors:

a. The various woods on the battlefield are primarily comprised of what are called “oak-hickory” forest types (1), which is to say that oak trees – especially white oaks – and hickory trees – mostly pignut and shagbark – are the predominant species. And these trees grow very slowly, and live for a very long time, up to and 0ver 250 years under favorable conditions.

b. The ground underneath the battlefield is very rocky. Boulders are everywhere, especially on the part of the battlefield that lies south of the town: Cemetery Ridge, the Wheatfield, Rose Woods, Culp’s Hill, and the Round Tops all lie on a geological table of bedrock known as the Gettysburg Sill, which is characterized by a thin soil layer and lots of rock. (2) Trees like oak and hickory have no problem growing in such soil, but because they have a harder time absorbing water and nutrients from the ground, they grow even more slowly than usual. The result is scores of 200-year-old trees with diameters of a yard or less. It is the very fact that there are few “large” trees that has led a generation of park officials and visitors to assume there were no more than a dozen or so witness trees in Gettysburg.

c. None of this would have mattered, however, if the trees on these woodlots had undergone harvesting in the decades after the battle. But thanks to the foresight of men like David Wills, who began a movement, often supported with their own money, almost immediately after the battle ended, to preserve the very land, including the woods, on which the men of north and south collided in 1863, most of the major areas of forest which experienced the heaviest fighting – Herbst Woods, Rose Woods, the Round Tops, Culp’s Hill – have been saved the ignominy of being denuded of trees.

(1) Maryland Department of Natural Resources website. Glossary of Forestry Terms. Retrieved May 29, 2023:
(2) Auwaerter, John et al. Cultural Landscape Report for First Day – Union 1st Corps Battlefield. Gettysburg National Military Park, Olmsted Center for Landscape Preservation, National Park Service, Boston, Massachusetts 2021. Page 11.