A slender, strongly aromatic shrub, to 2 metres tall.
It grows in dry sclerophyll forests including rainforest, often in gullies or near watercourses, mainly on the coast of New South Wales and mostly south from around Newcastle; with some disjunct records further north and in Victoria and Queensland.
Branches are densely hairy.
Prostanthera have simple, opposite and usually odorous leaves (a typical Lamiaceae feature). In this species, leaves are in opposite pairs (rarely in 3-leaf whorls), more or less round but usually appear egg-shaped or ovate because the edges are rolled under, to 6 mm long and 1 mm wide.
Flowers have a shape described as labiate (applies to all Lamiaceae flowers) with 5 petals varying in their size, fused at their base, produced in leaf axils. One of the identification features for Prostanthera is that the 5 calyx parts (basal whorl of the flower) are fused into 2 lips.
In this species flowers are solitary in the leaf axils. The petals are to 7 to 8 mm long, fused for most of their length, mauve to blue, the tip often whitish; Flowering occurs in Spring.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
In a garden situation, this species needs perfect drainage and near to full sun to grow well. Mulch well. Prune after flowering. It is known to be cultivated.
Plants are available from some online nurseries and may be available from retail nurseries.
A Prostanthera in full bloom is a magnificent sight and there are so many colours to choose from for your garden. These plants are found in all states in varied soil conditions and climate and thus while it may be a challenge to grow some species many are easy in a garden situation.
A few basic growing tips are:
• Good drainage is essential. Raised beds ensure this
• Water new plants until established, weekly or as required.
• Do not over water, as this can induce root rot and fungal infestation.
• They prefer moist root runs.
• Plant drooping is an indicator of dryness
Positioning of prostantheras as border plants or near pathways is recommended as the mint odour is released when brushed against.
Plants may be grown from fresh seed. However, cuttings are frequently and reliably used, usually semi-hard wood or soft tip material, which strike well in spring or autumn.
Prostanthera is a diverse group of about 100 species, endemic to Australia, occurring in all states. There are still many unresolved taxa and species complexes, with new forms regularly being found. Natural hybrids occur between several species and most species appear to be capable of hybridizing when in cultivation. NSW currently has about 52 species, some of which are species-complex and others which are threatened with extinction.
Some 80% of mints contain aromatic oils within their leaves with oil of cineole being a major component. Prostanthera sieberi, P. incisa and P. staurophylla are quite pleasantly overpowering in their exudates when crushed. Oil from the leaves of some species is distilled for use in cosmetics and as soap additives.
Most Prostanthera species will regenerate from seed after fire with some species exhibiting an ability to reshoot from basal areas and stem buds. The exact response for this species is unknown.
Prostanthera – from the Greek prosthike (προσθήκη) which translates to “addendum”, and anthir (ανθήρ) meaning anther – referring to the anthers which have an appendage of tissue.
violacea – Latin meaning “violet-coloured” referring to the colour of the flowers.
NSW Flora Online (PlantNET) – Prostanthera violacea profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~violacea
Australian Native Plants Society Australia – Prostanthera information page
Wikipedia – Prostanthera violacea profile page
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.