Cliffs as high as 400 feet above the valley floor provide a desert-like environment for the eastern red cedar. At Milford Bluffs, in Hunterdon County, New Jersey, Prickly Pear can be found, as well as the endangered Green Violet and Smooth Veiny Peavine.
Rare northeastern U.S. Roseroot, an arctic-alpine herb, grows on shelves and increvices at Pennsylvania's Nockamixon Cliffs - the plant's southernmost reach. Rare species such as riverweed grow in Tohickon Creek PA, a stream of very high water quality.
Lush areas of willow, spirea, silk dogwood and alder shrubs can be found in the river corridor's floodplain. This riverside vegetation provides valuable habitat for birds, mammals, and shades the water for fish. The riverside vegetation also varies with the geology and soils in the river corridor.
In the upper reaches large-toothed aspen and gray birch can be found. Throughout most of the river corridor area, red maple, red oak, walnut, black cherry, sycamore and hemlock trees are present.