Casuarina equisetifolia

Subspecies incana near Rockhampton

Casuarina equisetifolia, commonly known as coastal she-oak, horsetail she-oak,<ref name="RBGS">Template:Cite web</ref> ironwood,<ref>Template:Cite web</ref> beach sheoak, beach casuarina, whistling tree<ref name="Boland">Template:Cite book</ref> or Australian pine<ref name="LP"/> 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 Template:Cvt long containing winged seeds (samaras) Template:Cvt long.

Description

Habit

Casuarina equisetifolia is an evergreen tree typically growing to a height of Template:Cvt, sometimes to Template:Cvt tall. The bark of young specimens is smooth and greyish, older trees have scaly, greyish-brown to black bark.<ref name="RBGS" /><ref name="foa"/>

Foliage

The foliage consists of slender, drooping branchlets up to Template:Cvt long, the leaves reduced to scale-like teeth Template:Cvt long, arranged in whorls of 7 or 8 (occasionally 6) around the branchlets. The sections of branchlet between the leaf whorls (the "articles") are Template:Cvt long and Template:Cvt wide.<ref name="RBGS" /><ref name="Boland" /><ref name="foa"/>

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.<ref name=foa/> Its male and female inflorescences are both shaped like catkins.<ref name="LP"/> Its male flowers appear in simple spikes Template:Convert long in whorls of 7 to 11.5 per cm (per 0.4 in), with anthers are Template:Cvt long, whereas its female flowers are Template:Cvt long on short, sparsely hairy peduncles.<ref name="RBGS" /><ref name="Boland" /><ref name="foa"/>

Fruit

The fruit is an oval woody structure Template:Convert long and Template:Convert in diameter when mature, superficially resembling a conifer cone made up of numerous carpels. Each carpel contains a single small winged seed Template:Convert long.<ref name="RBGS" /><ref name="Boland" /><ref name=foa>Template:Cite web</ref>

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.<ref name=APNI>Template:Cite web</ref><ref name="L.">Template:Cite book</ref> The specific epithet equisetifolia means 'horsehair-leaved'.<ref name="Boland" />

In 1873, George Bentham described Casuarina equisetifolia var. equisetifolia and C. equisetifolia var. incana in Flora Australiensis,<ref name="Benth.">Template:Cite book</ref> and in 1982, Lawrie Johnson changed the names to subspecies equisetifolia and incana respectively, in the Journal of the Adelaide Botanic Gardens:<ref name="JABG">Template:Cite journal</ref>

• Casuarina equisetifolia L. subsp. equisetifolia,<ref name="APC1">Template:Cite web</ref> a tree Template:Cvt high, the articles Template:Cvt long and Template:Cvt wide with 8 to 10 teeth Template:Cvt long, the male spikes Template:Cvt long, the cones Template:Cvt long and Template:Cvt wide on a peduncle Template:Cvt long.<ref name="foa1">Template:Cite web</ref>
• Casuarina equisetifolia subsp. incana (Benth.) L.A.S.Johnson.<ref name="APC2">Template:Cite web</ref> a tree Template:Cvt high, the articles Template:Cvt long and Template:Cvt wide with 8 to 10 teeth about Template:Cvt long, the male spikes Template:Cvt long, the cones Template:Cvt long, Template:Cvt wide and densely covered with white to rust-coloured hairs, on a peduncle Template:Cvt long.<ref name="RBGS" /><ref name="foa2">Template:Cite web</ref> The epithet incana means 'white' or 'hoary'.<ref name="Stearn">Template:Cite book</ref>

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<ref name="Rumphius">Template:Cite book</ref> and there are no type specimens.<ref name="dcceew">Template:Cite book</ref>

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.<ref name="LP">Template:Cite web</ref>

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.<ref name="POWO" /><ref name="Boland" /> 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.<ref name="POWO" /><ref name="Boland" /><ref name="foa1" />

Subspecies incana grows on rocky headlands near the coasts of eastern Queensland and New South Wales as far south as Laurieton.<ref name="RBGS" /><ref name="Boland" /><ref name="foa2" /><ref name="CIFR">Template:Cite web</ref>

Casuarina equisetifolia has been introduced to many other continents and islands.<ref name="POWO" /> 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.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref name="ARS">Template:Cite web</ref> It is also regarded as being invasive in South Africa.<ref>Template:Cite web</ref>

Ecology

Casuarina equisetifolia is an actinorhizal plant able to fix atmospheric nitrogen<ref name="Wild Singapore">Template:Cite web</ref> through a symbiotic relationship with strains of Frankia, a actinomycete hosted in nodules on its roots.<ref>Template:Cite journal</ref>Template:Rp

Uses

Besides its ornamental uses, Casuarina equisetifolia has also been explored for its potential in remediation of textile dye wastewater. The leaves were found to be useful as absorbent material for the removal of textile dyes such as reactive orange 16,<ref name="Bharti">Template:Cite journal</ref> rhodamine B,<ref>Template:Cite journal</ref> methylene blue, malachite green<ref>Template:Cite journal</ref> and methyl violet 2B.<ref>Template:Cite journal</ref> Similarly, the dried cone was also reported to be able to remove rhodamine B<ref>Template:Cite journal</ref> and methyl violet 2B.<ref>Template:Cite journal</ref> The bark was reported to be able to remove methylene blue.<ref>Template:Cite journal</ref> Even the seed was found to be useful in dye removal of neutral red and malachite green.<ref>Template:Cite journal</ref> The carbon derived from the cones of C. equisetifolia was found to be a good absorbent for landfill leachate,<ref>Template:Cite journal</ref> while another laboratory also reported good absorbency for copper ions from aqueous solution.<ref>Template:Cite journal</ref> Line planting of C. equisetifolia trees in coastal areas has been known to help control the force of the wind. In countries like India, it has been known as a suitable species for wasteland development.Template:Citation needed

Culture

In the Philippines, the town of Agoo is named after the tree (known as agoho or aroo in the Ilocano language).<ref name="Sals">Template:Cite book</ref>

Gallery

• 
  Branchlets and male spike
• 
  Mature female cones
• 
  Samara
• 
  Male spikes

See also

• Pinus kesiya, the Khasi or Benguet pine
• Allelopathy

External links

• NT Flora: Casuarina equisetifolia. Northern Territory Government.