Casuarina equisetifolia
Casuarina equisetifolia, commonly known as coastal she-oak, horsetail she-oak, ironwood, 'beach sheoak, beach casuarina, whistling tree or Australian pine' is a species of flowering plant in the family Casuarinaceae and is native to Australia, New Guinea, Southeast Asia and India. It is a small to medium-sized, monoecious tree with scaly or furrowed bark on older specimens, drooping branchlets, the leaves reduced to scales in whorls of 7 or 8, the fruit long containing winged seeds long.
Description
Habit
Casuarina equisetifolia is an evergreen tree typically growing to a height of, sometimes to tall. The bark of young specimens is smooth and greyish, older trees have scaly, greyish-brown to black bark.Foliage
The foliage consists of slender, drooping branchlets up to long, the leaves reduced to scale-like teeth long, arranged in whorls of 7 or 8 around the branchlets. The sections of branchlet between the leaf whorls are long and wide.Flowers
This species of Casuarina is monoecious with male and female flowers produced on the same tree, unlike most other species of its same genus which are dioecious. Its male and female inflorescences are both shaped like catkins. Its male flowers appear in simple spikes long in whorls of 7 to 11.5 per cm, with anthers are long, whereas its female flowers are long on short, sparsely hairy peduncles.Fruit
The fruit is an oval woody structure long and in diameter when mature, superficially resembling a conifer cone made up of numerous carpels. Each carpel contains a single small winged seed long.Taxonomy and naming
The genus Casuarina was first formally described in 1759 by Carl Linnaeus in Amoenitates Academicae and the first species he described was Casuarina equisetifolia. The specific epithet equisetifolia means 'horsehair-leaved'.In 1873, George Bentham described Casuarina equisetifolia var. equisetifolia and C. equisetifolia var. incana in Flora Australiensis, and in 1982, Lawrie Johnson changed the names to subspecies equisetifolia and incana respectively, in the Journal of the Adelaide Botanic Gardens:Casuarina equisetifolia L. subsp. equisetifolia, a tree high, the articles long and wide with 8 to 10 teeth long, the male spikes long, the cones long and wide on a peduncle long.Casuarina equisetifolia subsp. incana L.A.S.Johnson. a tree high, the articles long and wide with 8 to 10 teeth about long, the male spikes long, the cones long, wide and densely covered with white to rust-coloured hairs, on a peduncle long. The epithet incana means 'white' or 'hoary'.
There is some doubt as to whether Linnaeus' publication of C. equisetifolia is valid, since he based his description solely on Rumphius's description of Casuarina litorea in Herbarium Amboinense and there are no type specimens.
This species is sometimes given the common name "Australian pine" because it has features that seem superficially like those of a pine, but it is not a conifer.
Distribution and habitat
Casuarina equisetifolia subsp. equisetifolia grows near the sea, behind beaches and near estuaries, sometimes on rocky headlands in Australia, New Guinea, Southeast Asia and India. The species is native to India and Bangladesh in South Asia; Myanmar, the Andaman Islands, Nicobar Islands, Vietnam, Thailand, Cambodia, Peninsular Malaysia, the Philippines, Borneo, Java and the Lesser Sunda Islands, islands in the South China Sea, Sulawesi and Sumatra in Southeast Asia; the Carolines, Fiji, the Marianas, the Marshall Islands, New Caledonia, Samoa, Solomon Islands, Tonga, Tuvalu and Vanuatu in the Pacific Ocean; New Guinea; and New South Wales, the Northern Territory, and Queensland in Australia.Subspecies incana grows on rocky headlands near the coasts of eastern Queensland and New South Wales as far south as Laurieton.
Casuarina equisetifolia has been introduced to many other continents and islands. It is an invasive species in the United States, but biological control by insects, including by a Selitrichodes wasp and Carposinidae and Gelechiidae moths, has been effective. It is also regarded as being invasive in South Africa.