Beach Sheoak

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.

Casuarina equisetifolia is an actinorhizal plant able to fix atmospheric nitrogen through a symbiotic relationship with strains of Frankia, a actinomycete hosted in nodules on its roots.

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, rhodamine B, methylene blue, malachite green and methyl violet 2B. Similarly, the dried cone was also reported to be able to remove rhodamine B and methyl violet 2B. The bark was reported to be able to remove methylene blue. Even the seed was found to be useful in dye removal of neutral red and malachite green. The carbon derived from the cones of C. equisetifolia was found to be a good absorbent for landfill leachate, while another laboratory also reported good absorbency for copper ions from aqueous solution. 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.

In the Philippines, the town of Agoo is named after the tree (known as agoho or aroo in the Ilocano language).