The Beach Pea (Lathyrus maritimus) grows in sandy dune areas and is a perennial. It helps keep sand in place with it's root system, and produces a pretty pink or purple flower. It is a member of the pea family and grows pods with peas. These peas are toxic to people, however, as they contain a paralyzing agent. Butterflies love the flowers. These are hardy plants that thrive in a salt air/salt water environment.