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A shrub reaching a height of 5 metres with a spread of 3 metres.
It is mainly a Victorian species, but grows in NSW as disjunct populations (which may be a different species). There are records west of Milton in Morton National Park, and in far south-east NSW close to the border. It grows over much of southern Victoria, to the north, west and east of Melbourne.
It typically grows in wet sclerophyll forest in sheltered as well as montane areas, on enriched soils.
Prostanthera have simple, opposite and usually odorous leaves. In this species, leaves are oval, about 3 centimetres long, aromatic with toothed margins. They are crowded, dull green above and paler beneath.
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, the flowers are mauve, to one centimetre long and carried in terminal racemes. Blooms are both conspicuous and profuse during the spring flowering period.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
Author’s notes:
Growth habit, foliage and flowers are all attractive features of this tall mintbush. It is known to be cultivated commonly and makes a very attractive shrub. It is reported to be hardy.
We grow the species as a background shrub in our dense shrubberies. The mature specimens in our cold climate garden reached about 4 metres tall with a spread of 4 metres. So, consider the location when planting.
Light pruning after flowering is advised and will help to keep the plant under control as well as promote spectacular flowering year-after-year.
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.
Cuttings produce roots quickly and enthusiastically.
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.
melissifolia – Latin – named for the foliage resembling Melissa – the Balm genus (including Lemon Balm – also in the Lamiaceae family).
This species is not considered to be at risk of extinction in the wild. It is rare in NSW.
NSW Flora Online (PlantNET) – Prostanthera melissifolia profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~melissifolia
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.
Bungalook Nursery – Prostanthera melissifolia profile page https://www.wcipp.org.au/prostanthera-melissifolia/