Actinostrobus acuminatus
Actinostrobus arenarius
Actinostrobus pyramidalis

Actinostrobus is a genus of coniferous trees in the Cupressaceae (cypress family). There are three species in the genus, all endemic to southwestern Western Australia. The most widely used common name is cypress-pine, a name shared by the closely related genus Callitris.

They are shrubs or small trees, reaching 3-8 m tall. The leaves are evergreen and scale-like, except young seedlings, where they are needle-like. The leaves are arranged in six rows along the twigs, in alternating whorls of three.

The male cones are small, 3-6 mm long, and are located at the tips of the twigs. The female cones start out similarly inconspicuous, maturing in 18-20 months to 1-2 cm long and wide, globular to acute-ovoid, with 6 thick, woody scales, arranged in two whorls of three, and a further 9-15 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.

External links

• Gymnosperm Database - Actinostrobus
• Arboretum de Villardebelle - Photos of cones