is a Casuarina genus of 17 tree species in the family Casuarinaceae, native to Australia, the Indian subcontinent, southeast Asia, islands of the western Pacific Ocean, and eastern Africa. It was once treated as the sole genus in the family, but has been split into four genera (see: Casuarinaceae). 
evergreen shrubs and trees growing to 35 m (115 ft) tall. The slender, green to grey-green twigs bearing minute scale-leaves in whorls of 5-20. The apetalous flowers are produced in small catkin-like inflorescences. Most species are dioecious, but a few are monoecious. The fruit is a woody, oval structure superficially resembling a conifer cone, made up of numerous carpels, each containing a single seed with a small wing.  The generic name is derived from the  Malay word for the cassowary, kasuari, alluding to the similarities between the bird's feathers and the plant's foliage, though the tree is called  rhu in current standard Malay.
Karen Louise Wilson and Lawrence Alexander Sidney Johnson distinguish the two very closely related genera, Casuarina and on the basis of: Allocasuarina
Casuarina: the mature samaras being grey or yellow brown, and dull; cone bracteoles thinly woody, prominent, extending well beyond cone body, with no dorsal protuberance; : the mature samaras being red brown to black, and shiny; cone bracteoles thickly woody and convex, mostly extending only slightly beyond cone body, and usually with a separate angular, divided or spiny dorsal protuberance. Allocasuarina
Ecology Casuarina species are a food source of the larvae of hepialid moths; members of the genus , including Aenetus and A. lewinii , burrow horizontally into the trunk then vertically down. A. splendens also feeds on Endoclita malabaricus Casuarina. The noctuid turnip moth is also recorded feeding on Casuarina.
Pedunculagin, casuarictin, strictinin, casuarinin and casuariin are ellagitannins found in the species within the genus.
, C. cunninghamiana and C. glauca have become C. equisetifolia naturalized in several countries, including Argentina, Bermuda, Cuba, China, Egypt, Israel, Iraq, Mauritius, Kenya, Mexico, Brazil, South Africa, the Bahamas,  Uruguay and then invasive species.  The species has nearly quadrupled in southern  Florida between 1993 and 2005, where it is known as Australian pine.
 C. equisetifolia is widespread in the Hawaiian Islands where it grows both on the seashore in dry, salty, calcareous soils and up in the mountains in high rainfall areas on volcanic soils. It is also an invasive plant in Bermuda, where it was introduced to replace the windbreaks killed by a scale insect in the 1940s. Juniperus bermudiana
Casuarina comprises the following species:     
Casuarina collina Poiss. ex Pancher & Sebert
Casuarina cristata Miq. (northeastern Australia: Queensland, New South Wales).
Casuarina cunninghamiana Miq. – river she-oak (northern and eastern Australia: Northern Territory to New South Wales)
Casuarina equisetifolia L. – beach she-oak, common ironwood, Australian pine (Florida), casuarina, whistling pine  (northern Australia, southeastern Asia, doubtfully native to  Madagascar), in (Bengali), ? (gaali mara) in Kannada.
Casuarina glauca Sieber ex Spreng. grey she-oak, longleaf ironwood, saltmarsh ironwood, swamp oak (New South Wales)
Casuarina grandis L.A.S.Johnson ( New Guinea)
Casuarina junghuhniana Miq. ( Indonesia)
Casuarina obesa Miq. (southern Australia: southwestern Western Australia, New South Wales [one site, now extirpated], Victoria)
Casuarina oligodon L.A.S.Johnson (New Guinea)
Casuarina orophila L.A.S.Johnson
Casuarina pauper F.Muell. ex L.A.S.Johnson (Australia)
Casuarina potamophila Schltr.
Casuarina tenella Schltr. Casuarina teres Schltr.
Species names with uncertain taxonomic status
The status of the following species is unresolved:
Casuarina defungens L.A.S. Johnson
Casuarina hexagona Dehnh.
Casuarina litorea Rumph.
Casuarina lucida Dehnh. Casuarina prisea Miq.
Formerly placed here
^ a b c
Australian Plant Name Index (APNI): IBIS database. Centre for Plant Biodiversity Research, Australian Government. Retrieved 3 November 2018. Casuarina
^ a b Linnaeus, C. (1759), Amoenitates Academicae 4: 143
^ a b c Flora of Australia:
Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan Publishers. ISBN . 0-333-47494-5
Quattrocchi, Umberto (2000). . I A-C. CRC Press. p. 456. CRC World Dictionary of Plant Names ISBN . 978-0-8493-2675-2
Wilson, K. L.; Johnson, L. A. S. (1989). "Flora of Australia online: Casuarinaceae". ABRS, Commonwealth of Australia . Retrieved 2018.
Okuda, T.; T. Yoshida; M. Ashida; K. Yazaki (1983). "Tannins of . Casuarina and Stachyurus species. I: Structures of pendunculagin, casuarictin, strictinin, casuarinin, casuariin, and stachyurin" Journal of the Chemical Society (8): 1765-1772.
"Archived copy". Archived from the original on 2011-07-06 . Retrieved . CS1 maint: archived copy as title ( link)
^ USFS FEIS:
^ USDA Forest service:
^ a b IFAS:
SRFer Mapserver Archived 2007-09-07 at the Wayback Machine
^ a b
"Casuarina (. Casuarina equisetifolia)" Department of Conservation. Government of Bermuda. Archived from the original on 2010-03-05 . Retrieved .
^ a b
"GRIN Species Records of . Casuarina" Germplasm Resources Information Network. United States Department of Agriculture. Archived from the original on 2009-01-20 . Retrieved .
". Casuarina" Integrated Taxonomic Information System . Retrieved .
^ a b
"The Plant List entry for . Casuarina" . The Plant List, v.1.1 Royal Botanic Gardens, Kew and the Missouri Botanical Garden. September 2013 . Retrieved 2020.
Govaerts R. ". Casuarina L." Plants of the World Online. Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved 2020.