Big Trees: Big Deal!

Trees! We enjoy their beauty and the shade they provide. We rely on them for the air that we breathe as they convert carbon dioxide into oxygen. They play a critical role in the ecosystem by removing pollutants from the atmosphere, storing carbon, which mitigates climate change, managing erosion and stormwater runoff, and providing food, shelter, and reproductive sites for wildlife. Where trees are concerned, bigger is actually better. In the past, it was thought that trees became less productive as they aged, but new studies show that is not necessarily the case. The biggest trees increased both their growth rate and the amount of carbon they sequestered as they aged. Due to their size, they generate more seeds, help forests to resist disturbances, and provide more habitat for wildlife. This highlights the importance of preserving our largest trees. Fortunately, long before this research was available, concerned citizens began a movement to conserve these giant treasures.

In 1940, with preservation as its goal, the American Forestry Association began a program to find and record our nation's largest trees. Founded in 1875 by physician and horticulturist Dr. John Aston Warder, it began as a citizens' organization for the advancement of intelligent management and use of the nation's forests. It advocated science-based strategies to conserve these forests for years to come. At that time, due to increased demands for lumber to support war efforts and some early recognition of pests and diseases, there was a real fear of losing large specimen trees to massive deforestation. This led the organization to create a national effort to search for the largest specimens of trees in the country and to make them known, appreciated, and protected. The focus was not necessarily on historic or "famous" trees like the California redwoods, but lesser-known giants not found on protected federal or state land — those held in private ownership.

Inspired by the destruction of a towering yellow poplar in western North Carolina, forester Joseph L. Stearns led the American Forestry Association's charge to find and save the largest trees in the United States. He recounted that tree's history in an article published in 1940. The story begins in the 1790s, as early Americans settled in western North Carolina and began clearing many of the hardwood trees covering the mountains, initially to clear land for homes and later for timber. At that time, logs were transported by oxen, which limited the size of trees that could be harvested and transported. This limitation left the largest trees standing. However, with the invention and implementation of the modern tractor, larger trees were beginning to be harvested. Fifteen miles northwest of Asheville, on the slope of Craggy Mountain, grew a massive yellow poplar that had been described by many as "the largest yellow poplar in the world". Even with early mechanized equipment, this tree was too big to handle. Left standing, the tree developed an open cavity on one side of the trunk. Still alive and producing blossoms every year, the cavity became large enough that visitors would assemble in groups inside its trunk. In 1934, tragedy struck when the tree succumbed to fire and toppled to the ground. The cause of the fire was attributed to squirrel hunters who, when seeking shelter earlier in the day, started a fire inside the hollow trunk and neglected to extinguish it completely.

In the 1940 September issue of "American Forests", American Forestry Association's monthly publication, its editor, Ovid Butler, refers to the undertaking as "a treasure hunt of sorts," and indeed it was, as these trees are national treasures. In 1941, the "Report on American Big Trees for 1941" was published, listing the largest of 103 species of trees that had been found. The most recent list, published in 2024, now includes 548 trees. Trees considered for inclusion fall into two categories: native and naturalized, and culturally important yet non-native. Naturalized species must be able to reproduce without human intervention and form ecological relationships in their environment while posing no significant negative impact on the native flora. Culturally important, non-native trees either require human intervention to reproduce or have had a documented negative impact on the native ecosystem, yet are commonly planted or occur in the urban environment.

Initially, inclusion was based mainly on the circumference of the tree, measured 4 feet from the ground. Currently, there is a point system. Trees are scored on three measurements: height, measured from the highest point on the tree straight down to the ground; circumference; and average crown spread in diameter or radius. Admission to the registry is based on a combined total point score. Of course, as trees grow larger, more complex, and intricate, they can become harder to accurately measure as it becomes difficult to physically perform the task.

Over the years, the program's administration has changed, but its goals have remained the same. The American Forestry Association changed its name to American Forests in 1992. In January 2024, the School of Natural Resources at the University of Tennessee Institute of Agriculture officially became the new home of the program. Not surprisingly, the tree with the highest point score is General Sherman, a giant sequoia (Sequoiadendron giganteum), located in the Giant Forest Grove of Sequoia National Park. It is, by volume, the largest known single-stem tree currently living, estimated to be up to 3,200 years old. Tiny by comparison, the tree with the lowest point score is a southern bayberry (Myrica caroliniensis), 14 feet tall with a trunk circumference of 6 inches. The tallest champion is a 321-foot-tall coastal redwood (Sequoia sempervirens) in California, and the shortest is a 9-foot jumping cholla (Cylindropuntia fulgida) in Florida. Visit the National Champion Tree Program website for a complete listing and historical registers.

There are only three trees located in Pennsylvania that are on the national registry: a balsam fir (Abies balsamea), water locust (Gleditsia aquatica), and witch hazel (Hamamelis virginiana). None are publicly accessible. If a visit to Virginia to see the largest tulip poplar (Liriodendron tulipifera), Maine to see the largest eastern white pine (Pinus strobus), or North Carolina to see the largest Canadian hemlock (Tsuga canadensis) is not in your travel plans, you still have the chance to visit big trees closer to home. Many states, including Pennsylvania, have their own lists of big trees. The PA Big Tree Program is managed by the Pennsylvania Forestry Association. The program's goals also include conserving, preserving, and promoting our beautiful trees here in Pennsylvania. While not nearly as large as General Sherman, the Tyler Arboretum is home to Pennsylvania's largest giant sequoia. Unlike the three trees on the national registry, many of Pennsylvania's big trees are on public land. For a complete list (with the ability to select by genus, species, and county), visit the Champion Trees of Pennsylvania website.