Beach grass represents a specialized group of vegetation uniquely adapted to thrive in harsh, sandy environments. This resilient plant forms the first line of greenery on many shorelines. It survives the constant shifting of sand, intense winds, and the drying effects of a maritime climate where other plants cannot establish themselves. These grasses are recognized by their stiff, upright stems and rolled leaves, creating the distinctive, tough clumps that dot the foredunes. They act as a foundational species for entire dune ecosystems.
Official Names and Identity
The plants commonly known as “beach grass” belong primarily to the genus Ammophila. The most widespread common name used to describe the entire genus is Marram Grass. Two species are particularly relevant to the coasts of North America and Europe.
The European species is Ammophila arenaria, known as European beachgrass or European marram grass. The species native to the eastern North American seaboard and the Great Lakes is Ammophila breviligulata, commonly called American beachgrass or American marram grass. Both species are perennial pioneer species, adapted to coastal habitats where soil nutrients are low and exposure is high.
The Grass’s Function in Dune Stabilization
The primary function of beach grass is its ability to build and stabilize coastal sand dunes, protecting the land from wave energy and wind erosion. This process is driven by an extensive, creeping system of underground stems called rhizomes. These rhizomes spread both horizontally and vertically, forming a dense mat that effectively knits the loose sand together.
The above-ground foliage acts as a physical barrier to wind. When wind-blown sand encounters the stiff leaves and stems, its speed decreases, causing the sand particles to drop and accumulate around the plant. This accumulation stimulates the growth of new, vertical rhizomes and shoots, allowing the plant to escape burial. American beachgrass can tolerate being buried by as much as one meter of sand in a single year. This continuous cycle of sand trapping and vertical growth results in the formation of the distinctive foredunes, which serve as natural coastal barriers.
Differences Between American and European Species
While both the American (A. breviligulata) and European (A. arenaria) species build dunes, they exhibit different growth patterns. A. arenaria typically forms denser tussocks and grows shoots mostly from vertical rhizomes, creating dunes that are taller and steeper. Ammophila breviligulata, in contrast, has more horizontally growing rhizomes, resulting in dunes that are shorter and wider.
A distinguishing feature is the ligule, a small flap of tissue at the base of the leaf blade: A. arenaria has a long, pointed ligule, while A. breviligulata has a short, flat-topped one. Geographically, A. arenaria is native to Europe and North Africa, but it was introduced to the Pacific coast of North America in the mid-1800s for stabilization. This introduction led to its establishment as an invasive species in some areas, where it can outcompete native dune flora and disrupt natural processes. On the West Coast, the two species have even hybridized, creating a new, highly productive grass.