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Gulf coast searocket, Cakile constricta, is a sprawling herbaceous plant native to beaches along the US gulf coast between Texas and Florida. It grows in the harsh “coastal strand zone,” that is, the sandy shore between the high tide line and dunes closest to the ocean. Here, it is exposed to hot sun, salt spray, and is sometimes submerged by ocean tides. It also occasionally occurs in wetlands and the edges of saltmarshes. As part of the mustard family (Brassicaceae), gulf coast searocket is sometimes called saltwater mustard.
Gulf coast searocket grows as an annual low shrub, reaching about 24 inches (60 cm) in height. It sometimes grows prostrate (lying down) rather than erect. Its many branches bear fleshy oval-shaped leaves, which store water, a limited commodity in its environment. Between April-October, small white or lavender flowers with four petals and a yellow center bloom at the tips of the branches.
In the spring, ridged, cylindrical fruits shaped (vaguely) like rockets grow on alternating sides of the stems. When ripe, the fruits get washed into the ocean. The seeds are water-dispersed in these buoyant fruit, which are well-adapted to traveling long distances in water before waves return them to shore. Once back on the beach they get buried in sand, and the single seed breaks out of its salt-saturated fruit to germinate.
Cakile constricta is one of just a few species that dominate the relatively barren sandy coastal strand zone of the southeastern US. It grows alongside other pioneer species of this zone, including sea oats (Unica paniculata), coastal panicgrass (Panicum amarum), seaside primrose (Oenothera humifusa) and seashore elder (Iva imbricata). Together, these plants play an important role in capturing blowing sand to begin building of new dunes.
The seeds and fruit capsules of gulf coast searocket comprise a significant part of the spring diet of beach mice (Peromyscus polionotus), replacing the seeds of dune grasses, which are available in the fall.