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 cruciflora is an erect shrub to about 1.5 metres in height by a similar width. The leaves are oval shaped, greyish-green, about 15 mm long and often distinctly curved inwards. The white flowers are unusual in having the shape of a cross – they are about 15-20 mm in diameter and are seen in spring.
P cruciflora is not well known in cultivation, possibly because it is not as spectacular in flower as some of the other mint bushes. However, the unusual flowers make it an interesting plant for the garden. It prefers well drained soils in a sunny or semi shaded location and should not be allowed to dry out.
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: M Parkes – Australian National Botanic Gardens