Actinostrobus is a genus of conifers in the Cupressaceae (cypress family). Common names include cypress, sandplain-cypress and cypress-pine, the last of these shared by the closely related genus Callitris. There are three species in the genus, all endemic to southwestern Western Australia: Actinostrobus acuminatus - Moore cypress-pine, Dwarf cypress, Creeping pine Actinostrobus arenarius - Bruce cypress-pine, Sandplain cypress Actinostrobus pyramidalis - King George's cypress-pine, Swan river cypress, Swamp cypress, Western Australian swamp cypress. This is the typical species of the genus. Description. Cypress-pines are shrubs or small trees, reaching mature heights of 10 to 25 feet (3 - 8 m) tall. The leaves are evergreen, of two forms; juvenile needle-like leaves 0.4 to 0.8 inch (10 - 20 mm) long on young seedlings (but occasional into adulthood in A. acuminatus), and scale-like adult leaves, 0.08 to 0.32 inch (2 - 8 mm) long with only the apex free. The leaves are arranged in six rows along the twigs, in alternating whorls of three.
The pollen cones are small, 0.12 to 0.24 inch (3 - 6 mm) long, and are located at the tips of the twigs. The seed cones start out similarly inconspicuous, maturing in eighteen to twenty months to 0.4 to 0.8 inch (10 - 20 mm) long and wide, globular to acute-ovoid, with six thick, woody scales, arranged in two whorls of three, and a further 9 to 15 thin, sterile basal scales. The cones remain closed on the trees for many years, opening only after being scorched by a bushfire; this then releases the seeds to grow on the newly cleared burnt ground.
The closest relative of Actinostrobus is Callitris, which is much more widespread, occurring in most of Australia, and differs in its cones lacking the basal whorls of small sterile scales.
The wood of Actinostrobus is light, soft and aromatic, but the plants are too small for any significant use. They are occasionally planted as ornamental shrubs, but their use is restricted by the high risks imposed by their very high flammability in bushfires.
