This small rainforest tree is confined to a small area of eastern Australia. It is considered rare and contains chemicals with potential for pesticide development.
Introduction
Found in the biologically diverse subtropics of eastern Australia, the Southern Quassia is an undescribed species and has also been known as Quassia sp. A. The genus Quassia is a member of the family Simaroubaceae, which includes six Australian species as well as many others world wide. The best known example of the genus is the South American Quassia amara, the bark of which is rich in phytochemicals with medicinal and insecticidal properties. Quassia chips from this tree are commercially available and favoured by gardeners as the basis of a natural, though quite poisonous, insecticidal spray. According to Natural Standard, Quassia is used traditionally as a remedy for headlice, to expel intestinal worms and to treat malaria.
Description
The Southern Quassia is a shrub or small tree with narrow lance-shaped leaves that are green when mature but a striking dark pink in a new growth flush. The flowers are found in clusters on the stems or near the apices of small branches. The petals are red, but the flowers are small and inconspicuous. Fruits are about one centimeter long, fleshy, with colour varying from red to a dark purplish black. Bird dispersal of seed is likely, though no observations are documented. Plantnet provides a more detailed description.
Habitat and distribution
Southern Quassia grows in subtropical and warm-temperate rainforest and regrowth. It is frequently found isolated in paddocks where its rainforest habitat has been cleared. The Dorrigo area is its southern limit. In north-east New South Wales, Southern Quassia occurs around the Nightcap Range and in the area formerly covered by the Big Scrub rainforest. The species extends to south-east Queensland.
Potential uses
As the Southern Quassia and the better known Quassia amara are closely related, it is not surprising that pesticidal properties have been also been identified in the Australian species. Latif and co-workers, in 2000 (Biochemical Systematics and Ecology, Volume 28, Number 2, pp. 183-184(2)) found that a methanol extract of the aerial parts of the tree showed lethal activity against the two-spotted spider mite, peach/potato aphid and the root knot nematode.
Conservation status
In 1996, J.D Briggs and J.H. Leigh (Rare or Threatened Australian Plants, CSIRO, Canberra) considered the Southern Quassia to be rare. Its rainforest habitat has been severely depleted and fragmented, and threats include weed competition, grazing and fire. Landowners, community groups and conservation land managers are working to expand rainforest and remove threats so that this rare species can thrive in its natural habitat.
