Beach Plants and Sand Dunes Were Made for Each Other

We all know how pretty sand dunes are, but did you know that sand dune systems on the Florida and Alabama beaches are formed by wave and wind action and help to protect mainland areas from tropical storms and hurricanes?  The sand dunes, which have evolved over millions of years, actually help to absorb the vast energy created by storm waves and to minimize their damage.  During storms, sand erodes from the beaches and is deposited on shallow sandbars, while during calm weather, sand is returned to the shore in an ever-continuing cycle.  Waves and offshore winds are responsible for bringing sand to the shore in the first place, but it is obstacles such as plants and even driftwood that cause the sand to accumulate.  As sand continues to build up on the dunes, different species of plants begin to emerge that are specially adapted to the beach environment and help to stabilize the dunes.  In fact, without these specialized plants and vegetation, blowing sand would migrate inland in short order, and there would be no dunes!   As it turns out, the quality of coastal sand dunes goes hand in hand with beach plants and vegetation, which is a big key to the entire coastal ecological system, since sand dunes provide important food and shelter for numerous bird and animal species. Dune plants are specially adapted to living in their harsh environment, where they must contend with extremely hot temperatures, sandy soil that   is largely devoid of nutrients or moisture, and a continuous barrage of saltwater spray.  The specialized plants that grow naturally on sand dunes along the Alabama and Florida Gulf coasts are responsible for trapping sand around their roots and branches, thereby stabilizing the dunes and promoting new dune formation.  Along the Gulf of Mexico’s scenic coastline, there are many species of native plants growing among the sand dunes. Some of the more easily recognized beach plants include sea oats, beach elder, bitter panicum and Gulf bluestem.  Perennial grasses are the primary stabilizers of frontal dune systems, both on the Atlantic and Gulf coasts.   Of these, sea oats (Uniola paniculata) easily make up the most dominant plant species that grows on sand dunes. They are critical to the maintenance and well-being of sand dunes along the Gulf Coast. As any tried-and-true Gulf Coast enthusiast will tell you, sea oats are the tall, wheat-colored grasses that give coastal sand dunes such a large part of their identity.  In fact, it is the striking appearance of sea oats, particularly while in bloom, that has made protection of this plant necessary to avoid illegal harvest.  Sea oats are perennial, warm-seasonal grasses with tall stems and narrow, elongated leaves, and are native to coastal sand dunes from Virginia to Mexico. During the early fall, flower spikes appear that produce the seed heads.  This creeping species of grass also has an extensive underground root system, enabling it to grow seaward of sand dunes as well as behind the dune crest.  Ecologists now know that the submersion of sea oats under the sand actually stimulates their growth! Beach elder, also known as Seashore Elder or Seacoast Marshelder (Iva imbricata), is a low, vivid-green perennial shrub with multiple branches that   you often see growing on sand dunes along the Gulf Coast.  This woody shrub grows mainly on frontal dunes and reaches a height of 40 inches with upright stems.  It has narrow, alternating leaves ranging from 1/4 to 1/2 inch wide and approximately 2 inches long.  This beautiful shrub has small lavender blooms that first appear in late summer, and it continues blooming into early fall.  Beach elder is very beneficial to sand dunes since it tends to accumulate sand rapidly and typically produces low, rounded dunes. Bitter panicum (Panicum amarum), known in some areas as Running Beachgrass, is a tall perennial shore grass with narrow, elongated, silver-green leaves; it is found on sand dunes from Mexico to New England.   Given that its upright clumps generally stand out from other types of beach plant species, it’s generally not too hard to spot if you look closely.  The panicum family is actually a rather large genus of 450 grass species that grow in tropical regions throughout the world. The other beach grass that you have likely come across on your travels to the coast is called Gulf bluestem (Schizachyrium maritimum), considered to be the most important species of bluestem grass on the Gulf of Mexico. This is another perennial species of creeping grass that is readily identifiable by its silvery-blue leaves.  The seed heads of this species mature in late summer and are distinguished by dense, silvery hairs. The next time you visit the Gulf Coast, take a look around at the plants and vegetation. Only in that way can you begin to appreciate the natural harmony that exists between the beautiful beach plants and the magnificent sand dunes!

Published on Wednesday, December 10, 2014