Pine woods blanket ancient sand dunes of the Lower Eastern Shore. These low and inconspicuous dunes were built on the east side of larger rivers by strong northwest winds between 30,000 and 13,000 years ago.

One of the unusual plants of this dry habitat is the Hairy Snoutbean, Rhynchosia tomentosa, a member of the pea family. This perennial has three-part leaf, a square stem, and blooms in mid to late summer. Through a symbiotic association with soil bacteria that grow within their roots, many plants of the pea family convert nitrogen from the atmosphere into a form that is usable by the plants. This enables plants to grow in nutrient-poor environments such as these ancient sand dunes where other species cannot survive.

Hairy Snoutbean is near the northern limit of its range in Maryland. It is State Threatened, primarily because of habitat loss due to conversion to agriculture, residential development, and timber management.