Prostanthera is a genus of about 90 species which occur only in Australia. They are known generally as “mint bushes” because of the aromatic foliage of many species. As a member of the Lamiaceae, Prostanthera is related to a number of culinary herbs such as mint, thyme, oregano and sage.
Prostanthera teretifolia is usually a small shrub up to 1 metre high but occasionally may reach 2 metres. Leaves are linear and rounded in cross-section and up to 15mm long. They are grey-green in colour and highly aromatic. The flowers are usually deep purple (sometimes mauve) and flowering occurs mainly in spring. The plant is similar to another mint bush from the same general area, P.staurophylla. Some botanists consider that the two should be regarded as a single species.
This species has not been cultivated to a great extent but is a very attractive plant which deserves greater attention. Like many mint bushes it can be difficult to maintain in gardens for long periods. It prefers a well drained, moist position with some shelter from direct summer sun.
Prostantheras respond to well to annual fertilising after flowering and are not as sensitive as some other Australian plants to phosphorus.
Propagation is easy from cuttings but seed can be slow to germinate. In areas where the root-rot fungus Phytophthora cinnamomi is a problem, grafting onto the related Westringia fruticosa is recommended.
* EPBC Act = Environment Protection and Biodiversity Conservation Act 1999;
ROTAP = Rare or Threatened Australian Plants (Briggs and Leigh, 1988)
For further information refer the Australian Plants at Risk page
Photo: Brian Walters