The cactus species Leptocereus grantianus occurs only on Culebra Island, limited to a population of 50 plants along the southwest coast. This spineless cactus was discovered in 1932 by Major Chapman Grant. In 2003, efforts began to establish a second colony of the cactus.
In the dry coastal areas of Culebra Island, prickly pear cactus occur. Species of night-blooming cacti belonging to the genus Selenicereus are also found in this area. These clambering cacti often grow on sea-grape plants along banks and coasts on Culebra Island.
Several species of Turk's cap cactus occur in the coastal lowlands of Culebra Island. These cacti belong to the genus Melocactus and possess a hallmark reddish-brown, wooly structure at the top of the plant's body. This structure, known as a cephalium, resembles a tall turban. A Turk's cap cactus typically has a spiny green globular form and begins to produce a cephalium when it is ready to flower. Species of Pilosocereus, Stenocereus and Harrisia also grow in dry forest areas of the lowland region.
