''Actinostrobus'' is a genus of

conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ext ...

ous

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

s in the

Cupressaceae Cupressaceae is a conifer family, the cypress family, with worldwide distribution. The family includes 27–30 genera (17 monotypic), which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioeci ...

(cypress family). Common names include cypress, sandplain-cypress and cypress-pine, the last of these shared by the closely related genus '' Callitris''.

Species

There are three species in the genus, all

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to southwestern

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to t ...

: A 2010 study of ''Actinostrobus'' and ''Callitris'' has placed all three species of ''Actinostrobus'' within an expanded ''Callitris'' based on analysis of 42 morphological and anatomical characters. They are

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from tree ...

s or small

s, reaching tall. The leaves are

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, whic ...

, of two forms; juvenile needle-like leaves long on young seedlings (but occasional into adulthood in ''A. acuminatus''), and scale-like adult leaves, long with only the apex free. The leaves are arranged in six rows along the twigs, in alternating whorls of three. The male cones are small, long, and are located at the tips of the twigs. The female cones start out similarly inconspicuous, maturing in eighteen to twenty months to long and wide, globular to acute-ovoid, with six thick, woody scales, arranged in two whorls of three, and a further nine to fifteen 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

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...

s 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 Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

, 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.

References

* *Farjon, A. (2005). ''Monograph of Cupressaceae and Sciadopitys''. Royal Botanic Gardens, Kew. .
Gymnosperm Database - ''Actinostrobus''
{{Taxonbar, from=Q1472074 Flora of Western Australia Pinales of Australia Conifer genera