Highly effective antibacterial

Shrub or small tree to 10 metres high, in dry rainforest or in open forest, north from Ramornie on the Clarence River, NSW. Leaves ovate to more or less circular, to 6 cm long, margins mostly entire, upper surface dark green; lower surface grey and finely pubescent with long and short hairs, petiole 3-8 mm long, hairy. Male flowers in clusters of 3 or 4, female flowers solitary. The flowers of Petalostigma pubescens (the quinine bush or quinine tree) are tiny, fragrant, and colored a modest cream, yellow, or fawn. The plant is dioecious, meaning male and female flowers grow on separate trees: male flowers appear in small clusters of three or four, while female flowers grow alone. Petalostigma is a genus of plants under the family Picrodendraceae and the monogeneric subtribe Petalostigmatinae. It has seven species found in New Guinea and Australia.

Petalostigma pubescens male flowers. This male tree at Walton Bridge Reserve The Gap is very close to the bridge opposite Jevons Street. There is a female tree a few metres from the male tree. Photo: Robert Whyte

Medicinal and other uses

Despite the common name of Quinine Bush, Petalostigma pubescens does not contain quinine. It does contain bitter alkaloids and the smell of the bark is said to be reminiscent of quinine. Aboriginal people used its bark and fresh fruit as a medicinal wash, antiseptic and bitter tonic to treat sore eyes, toothaches, fevers, and bacterial infections. Research evaluated by the University of the Sunshine Coast in 2009 has validated traditional usage. Extracts from P. pubescens fruit and bark demonstrate broad-spectrum antibacterial activity against various strains, including drug-resistant bacteria like MRSA (methicillin-resistant Staphylococcus aureus). Note that the fruit loses its medicinal potency after drying.

Photo: Robert Whyte

Seed collecting and propagation

Fruit orange yellow, segmented, globular to egg-shaped 12-17 mm wide, fleshy layer often hairy and slightly lobed. Ripe between April and November. Gather fallen fruit or ripe from tree. Dry fruit, allow to split, remove seeds. Sow in well-drained soil, water regularly, protect from frost. May be slow to germinate. Can also be grown from cuttings.

Fruit close-up. Photo: Robert Whyte