Trees and Shrubs

Chestnut Oak — Northern Red Oak
National Park Service

Trees and shrubs are woody perennials, of which many species can be found in the Upper Delaware Region. Trees typically have a single stem, called the trunk, and lateral branches. Generally, trees have a trunk larger than two inches in diameter at four and a half feet above the ground. Shrubs are usually smaller than trees and have multiple woody stems arising near the ground.

The most common forest type found in the park, the Hemlock – Beech – Oak Forest, is home to Eastern Hemlock, American Beech, Sweet Birch, Chestnut Oak, and Northern Red Oak. This forest type compromises one-fifth of the park. The evergreen shrub, Great Laurel, also known as Great Rhododendron, is commonly found within these forests. Great Laurel has large white to pink bell-shaped flowers in the summertime. Great Laurel is evergreen, which means it maintains green foliage year-round. Other evergreens are found in these forests, like the Eastern Hemlock, an evergreen conifer. Conifers are characterized by their cones and needle or scale-shaped leaves. Other trees in the Hemlock – Beech – Oak Forest, such as American Beech, Sweet Birch, Chestnut Oak, and Red Oak, are deciduous trees, meaning they shed their leaves each year.

Nearly one-third of the park contains forest types dominated by oak trees. There are hundreds of different species of oak trees around the world. Common oak species in the park include White Oak, Scarlet Oak, Northern Red Oak, and Chestnut Oak. Oak trees prefer slightly acidic soil and are thus usually found on thin, rocky, acidic soil in the park. Most oak trees have lobed leaves that turn yellow or orange in the fall. Oak trees produce acorns, which is an important food source for wildlife like the Wood Duck.

Sycamore tree — Sugar Maple
National Park Service

Visitors may encounter trees like American Sycamore, Silver Maple, and Box Elder throughout the river floodplain. American Sycamore may be found on low terraces directly next to the river channel and experience frequent flooding. The bark of American Sycamore is uniquely mottled. The outer darker layers peel back to reveal lighter, almost white inner bark. Silver Maple and Box Elder are typically found on higher terraces along the river and experience less frequent flooding, only becoming inundated during more significant flood events. The leaves of Silver Maple appear bright green but have a silvery-white underside. Box Elder often has leaves with three leaflets, resembling Poison Ivy. Young Box Elder plants may be mistaken for Poison Ivy but can be distinguished by their green instead of reddish stems.

The higher elevation rocky ridges and summits in the park are often characterized by a dense shrub layer. These plant communities are created and maintained by fire. After a fire, the dense shrub layer is the first plant life to reappear. Then, as time goes on, more shrub species and even some trees may appear. Then, if fire comes back it restarts the process. Lowbush Blueberry, along with Blue Ridge Blueberry, are two of the dominant shrubs in these communities. Lowbush Blueberry has small berries that are very sweet and can be used to make jam. The Blue Ridge Blueberry is a host plant for the Brown Elfin Butterfly. Adult female butterflies lay eggs on the buds of Blue Ridge Blueberry, and once the caterpillars hatch, they feed on the flowers and fruit.

Hemlock Tree — Eastern Hemlock
National Park Service

The park is also home to the state trees of both New York and Pennsylvania. The state tree of New York is the Sugar Maple. In the park, Sugar Maple may be found alongside species such as White Ash and American Basswood. Sugar Maple is a large hardwood tree that usually ranges from 70 to 90 feet. In the summertime, the leaves are dark green, but in the fall change to a beautiful yellow or burnt orange color. The sap can be collected from Sugar Maple trees and boiled down to create maple syrup.

The state tree of Pennsylvania is the Eastern Hemlock. As mentioned previously, these trees are common in the park and found within the Hemlock – Beech – Oak Forest. The Eastern Hemlock has green needle-shaped leaves year-round and produces small cones, which ripen in the fall and then release seeds in the winter. They’re large, slow-growing trees that may live for hundreds of years. Currently, the Eastern Hemlock is threatened by the invasive insect Hemlock Wooly Adelgid. Trees infested with Hemlock Wooly Adelgid may suffer from needle loss, branch dieback, gray-tinted leaves, and eventually death.

The state flower of Pennsylvania, Mountain Laurel, can also be found in the park. Although Mountain Laurel is the state flower of Pennsylvania, it is a large evergreen shrub that can grow from six to ten feet. Mountain Laurel has beautiful cup-shaped flowers that appear in clusters and range from white to pink. It usually blooms in late spring to early summer. The flowers attract important pollinators like hummingbirds and butterflies.

Common tree and shrub species in the Upper Delaware Region include:

American Basswood (Tilia americana)

American Beech (Fagus grandifolia)

American Sycamore (Platanus occidentalis)

Blue Ridge Blueberry (Vaccinium pallidum)

Box Elder (Acer negundo)

Chestnut Oak (Quercus prinus)

Eastern Hemlock (Tsuga canadensis)

Eastern White Pine (Pinus strobus)

Great Laurel (Rhododendron maximum)

Lowbush Blueberry (Vaccinium angustifolium)

Mountain Laurel (Kalmia latifolia)

Northern Red Oak (Quercus rubra)