Actinostrobus pyramidalis, first described in 1845 by Friedrich Anton Wilhelm Miquel (1811-1871), is commonly known as King George's cypress-pine, Swan River cypress, or swamp cypress. It is the typical species of the Actinostrobus genus.
Description. King George's cypress-pine is an evergreen, coniferous shrub or small tree, reaching mature heights of 25 feet (8 m) tall. Bark is brown and smooth. Branchlets are divided into long, straight, slender branchlets.
The leaves are scale-like, up to 0.48 inch (12 mm) long except on young seedlings, where they are needle-like, often glaucous, and 0.28 to 0.32 inch (7 - 8 mm) long. 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, but mature in 18 to 20 months to 0.4 to 0.8 inch (1 - 2 cm) with a rounded apex. The cones open and release the seeds only upon drying. They tend to remain closed on the trees for many years, opening only if the branch, or the whole tree, dies. Bushfire kills swamp cypress, but it also causes a great many seeds to be released all at once, resulting in prolific regeneration. In one case, an isolated tree on Jeegarnyeejip Island was killed by fire, and the following winter there were 800 seedlings per square metre within a couple of metres of the original specimen, and about 150 per square metre ten metres away.
Distribution. This species is native to Australia - Western Australia where it is endemic and locally frequent in shrublands in sandplain country, from near Watheroo south to the Albany district, south-western WA.
