Seabeach Amaranth - Amaranthus pumilus
By Chris Daves, SC Master Naturalist
Seabeach amaranth is an annual herb belonging to the Amaranth family. The U.S. Fish and Wildlife Service first listed it as a threatened species in 1993.
The distribution of this species formerly included nine states located along the Atlantic Coast. Currently, the species is restricted to only three states: South Carolina, North Carolina and New York (Long Island). Most of the populations of seabeach amaranth are located in North Carolina. In South Carolina, populations are known to exist in Horry, Georgetown and Charleston Counties.
Its habitat includes the sandy substrates of coastal barrier beaches. It is found above the high tide line in the lower foredune area of non-eroding beach. Other locations include overwash flats and accreting spits at the end of the barrier islands.
It possesses thick, fleshy, oval-shaped leaves located at the end of the branch tips. Leaves range from 0.5 to 1 inch long and also have a hollow notch at the tip.
The prostrate stems originate from a taproot and form mats below or above the sandy surface. Flowers are found in clusters within the leaf axils. Seabeach amaranth is monoecious, containing both male and female flowers on the same plant. Its fruit is in the form of a smooth, bladder-like utricle. Its small black seeds are easily spread by wind and water. Seeds typically germinate in May. Both the flowers and fruits mature from June to frost.
Seabeach amaranth is often found mixed with sparse populations of sea rocket, Carolina saltwort, seashore elder and sea oats. However, it is intolerant of competition and does not occur in thickly-vegetated areas. It often grows in areas occupied by nesting shorebirds such as plovers, terns and skimmers.
The largest threat to the species is destruction of its habitat via man-made beach stabilization efforts. The construction of sea walls, bulkheads, jetties and revetments often cause further erosion of the lower foredune area. The species fares better when soft erosion control measures such as beach renourishment are used. Beach renourishment often enlarges the beach and thus creates more habitat for seabeach amaranth.
Hurricanes and strong storms which cause coastal erosion also contribute to habitat destruction. The number of plants fluctuate year to year based on coastal dynamics and the number of strong storms. In 1989, Hurricane Hugo wiped out an estimated 90% of the seabeach amaranth population in South Carolina.
Other threats to the species include webworm herbivory and impacts caused by recreational abuse such as excessive foot traffic or off-road vehicles.
Efforts to preserve the species include limiting the hard erosion control measures implemented along the coast. Other efforts are being made to create seed banks so that populations can be reestablished in suitable habitat. Restrictions on off-road vehicular traffic and pedestrian activities also help to protect this species.
An excellent location to view seabeach amaranth is the north end of Pawley’s Island in Georgetown County. It can be seen in multiple clusters just below the dunes south of the inlet separating Pawley’s Island from Litchfield. Although this area was hit hard by Hurricane Hugo, the seabeach amaranth population appears to be making a steady comeback.
Porcher, R.D., and D.A. Rayner. 2001. A Guide to the Wildflowers of South Carolina. University of South Carolina Press, Columbia. 551 pp.
Radford, A. E., H. Ahles, and C. R. Bell. 1978. Manual of the Vascular Flora of the Carolinas. UNC Press, Chapel Hill. 1,183 pp.