On barrier islands such as Assateague that are subjected to strong, salt-laden winds, tree and shrub growth is restricted both in size and location. Sheltered areas behind dunes allow tree and shrub communities to grow, but where the island is narrow or lacks protective dunes few or no species may exist.

Shrub communities on Assateague establish themselves on or behind dunes, in protected depressions, and along the edges of marshes, with characteristic species growing in each location depending on the levels of salinity and moisture present. One of the most distinctive shrubs of Assateague is beach heath (Hudsonia tomentosa), a dense, low shrub common to dunes and sandy areas along the eastern seaboard. It sometimes acts as a pioneer plant, providing cover that allows other species to become established. Beach heath blooms in May and June, producing numerous small, yellow flowers.

Taller shrub communities behind dunes are limited in height by salt winds blowing above the plants, which exert a natural pruning force. Wax-myrtle (Myrica cerifera), an evergreen whose berries are eaten by tree swallows and myrtle warblers, is the most common shrub in these protected areas. Marsh elder (Iva frutescens), which is capable of tolerating brackish or saltwater areas, dominates the shrub thickets surrounding salt marshes on the bay side of the island and marks the transition between upland and marsh.

In central portions of the island where shelter from overwash and salt winds allow, tree communities occur. The majority of large trees in these forests are evergreen, with loblolly pine (Pinus taeda) being the dominant. Interspersed among the pines are deciduous species such as red maple (Acer rubrum), sweetgum (Liquidambar styraciflua), persimmon (Diospyros virginiana), sassafras (Sassafras albidum), and several species of oak (Quercus sp.). Other evergreen species present in the forests include American holly (Ilex opaca) and red cedar (Juniperus virginiana).