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A variable shrub that may reach a height of 5 metres by about 4 metres wide.
It has a large natural range, growing along the coast and inland of NSW, as far south as the very south-east corner of the State, extending to Mallacoota in Victoria (with further records to the west as far as the Geelong-area); extending to as far west as Griffith in NSW, east to Cowra, with a lot of records in the Sydney area (north of the harbour mainly), as well as Wisemans Ferry; extending in disjunct occurrences up the coast and inland, to as far north as Rockhampton-area is Queensland.
Prostanthera have simple, opposite and usually odorous leaves. In this species, the leaves are ovate to narrow-ovate, to 50 mm long by 10 mm wide (widest in the middle), mid to dark green with the lower surface paler and densely coverd with glands.
Flowers have a shape described as labiate (applied to all Lamiaceae flowers) with petals varying in their size, purple to lilac, produced in leaf axils. One of the identification features for Prostanthera is that the 5 calyx parts (sepals; basal whorl of the flower) are fused into 2 lips. In this species, flowers are to 1 cm long, bright mauve to purple or bluish-purple; arranged in terminal clusters or botryoids, occurring profusely in spring.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
Author’s notes:
A useful screening plant. Also try planting beside paths so the foliage aroma is released as you brush past. The specimens in our garden only reach two metres. Judicious pruning will limit the height and prevent the plant becoming straggly.
P. ovalifolia is probably the most widely cultivated mint bush and most popular. It is typically easy to grow, on a range of soils. During dry periods plants have a tendency to wilt. Mulching and watering will bring plants bouncing back.
This can be a very showy flowering plant after it has been grown for two years or more, with pruning to shape. It can turn out to be a large plant – so allow some room to grow.
Does best in some sun / dappled shade.
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.
Likely regenerates from seed after fire, possibly after 12 months.
Prostanthera – from the Greek prosthike (προσθήκη) which translates to “addendum” (root of prosthetic), and anthir (ανθήρ) meaning anther – referring to the anthers which have an appendage of tissue.
ovalifolia – Latin – referring to the roughly oval-shaped leaves of the species.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Prostanthera ovalifolia profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~ovalifolia
Gardening with Angus – Prostanthera ovalifolia profile page https://www.gardeningwithangus.com.au/prostanthera-ovalifolia-oval-leaved-mint-bush/
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.