Pennsylvania, often called “Penn’s Woods,” boasts a deep forest heritage, with over 60% of the state covered in woodlands. This vast expanse is defined by native tree species, which evolved over millennia to thrive in the region’s climate and soil conditions. A tree is classified as native if it naturally occurred in this area before European settlement, without human introduction. Understanding these indigenous species is fundamental to supporting the state’s local ecology and biodiversity.
Defining Native Trees in Pennsylvania’s Biome
Pennsylvania’s biome primarily falls within the Eastern Temperate Forests ecoregion, characterized by a mix of broadleaf deciduous trees and conifers. Native trees play a specialized role within this established ecological web. They provide the specific food and shelter required by local wildlife, including native insects, birds, and mammals, which have co-evolved alongside them. For example, the leaves of native trees are often the only larval host plants for specific native butterfly and moth species. Native root systems are adapted to Pennsylvania’s soil composition and seasonal rainfall patterns, which helps maintain soil health and prevent erosion more effectively than non-native alternatives. The dominant forest type across the lower two-thirds of the state is the Oak-Hickory forest.
Prominent Native Hardwood Species
Hardwood, or deciduous broadleaf, species constitute approximately 90 percent of Pennsylvania’s forest cover. Native Oaks are a foundational component of this landscape, particularly the abundant Northern Red Oak and White Oak. Northern Red Oak leaves have pointed lobes ending in small bristles, and its mature bark is dark with light-colored vertical furrows. The White Oak is recognized by its lobed leaves without bristles and its lighter, ash-gray bark.
Maples are also ubiquitous, with the Red Maple being the most common tree species statewide. This tree features simple, opposite leaves with three to five pointed lobes and is known for its brilliant scarlet or orange fall foliage. The Sugar Maple is prized for its sap used in maple syrup production and its striking yellow, orange, or red autumn colors, thriving on moist, wooded slopes.
The Black Cherry is highly valued for its dark, reddish-brown wood, making it the state’s most economically important native species. Its leaves are simple, alternate, and shaped like pointed spearheads. Another significant group is the Hickories, including the Shagbark Hickory, easily identified by its unique, peeling strips of gray bark. This group, along with Mockernut, Pignut, and Bitternut Hickories, produces nuts that are a critical food source for numerous wildlife species.
Native Evergreen and Understory Species
Native conifers, or evergreens, provide year-round cover and are structurally distinct from deciduous hardwoods. The Eastern Hemlock, Pennsylvania’s official state tree, is a prominent example, preferring cool, moist woods and featuring soft, flat needles and small cones. The Eastern White Pine is the only native pine in the state that bears its soft, flexible needles in bundles of five.
Understory trees are smaller species that grow beneath the canopy of larger hardwoods and evergreens, often providing early-spring blooms or showy fruit. The Flowering Dogwood is a prized understory tree, known for its large, white or pink petal-like bracts in spring and clusters of bright red berries in the fall. The Eastern Redbud creates a stunning display, with clusters of pink-purple blossoms emerging directly from the branches before its heart-shaped leaves appear.
The Allegheny Serviceberry produces drooping clusters of white flowers very early in the spring, followed by edible, dark reddish-purple berries that are a food source for birds and small mammals. These smaller trees are essential for adding structural diversity to the forest.
Geographic Influences on Tree Distribution
Pennsylvania’s varied topography and geology create distinct ecological zones that influence where specific native trees thrive. The state is divided into major physiographic provinces: the low-lying Piedmont region in the southeast, the rugged Ridge and Valley system centrally, and the higher Allegheny Plateau in the north and west. These differences lead to varied soil types, elevations, and microclimates.
The fertile, often limestone-based soils of the southeastern Piedmont region historically supported rich Oak-Hickory forests, which dominate the southern two-thirds of the state. Conversely, the Northern Hardwood Forest, characterized by species like Sugar Maple, American Beech, and Black Cherry, is found primarily in the northern third and at higher elevations along the Allegheny Front. The Ridge and Valley ecoregion, with its abrupt changes in elevation and parent rock material of sandstone and shale, supports communities adapted to drier, rockier slopes, such as those dominated by Chestnut Oak. These localized conditions mean that a tree species found statewide may have different population densities depending on the specific geographic zone.