An erect shrub to 4 metres tall to 2 metres wide, which is strongly aromatic.
Stems are hairy and glandular and often square.
It is confined to the Hunter Valley in NSW, near Scone, Cessnock and further south at St Albans, and is typically found on very shallow sandy soils on sandstone ridges and slopes, in dry sclerophyll woodlands.
It is a listed threatened species.
Prostanthera have simple, opposite and usually odorous leaves (a typical Lamiaceae feature). In this species, leaves are in opposite pairs or rarely in 3-leaf whorls, narrow egg-shaped, to shortly lanceolate, light green, to 50 mm long and to 12 mm wide, on a petiole to 7 mm long.
Flowers have a shape described as labiate (applied to all Lamiaceae flowers) with petals varying in their size. 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 arranged in terminal clusters with flowers having attached bracteoles, to 2 mm long that fall off as the flowers develop. The petals are fused into a tube, light pale-mauve to dark purple-mauve, to 12 mm long by about 10 mm wide. Flowers are typically darker on the inside, produced in September to October.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
Not readily known in cultivation but it is known to be cultivated. This might be due to it being a listed threatened species. May be able to be sourced from nurseries in time.
Likely needs a sandy well-draining soil to thrive. Grow in part-shade and prune lightly after flowering for best results.
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. Oil from the leaves of some species is distilled for use in cosmetics and as soap additives.
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. Some plants have been observed to reshoot from the basal parts of stems.
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.
cineolifera – Latin – named for the leaves bearing large amounts of cineol in the essential oils of the leaves.
This species is listed as threatened with extinction in the wild, at both the State and Commonwealth level, with the category of vulnearable.
NSW Flora Online (PlantNET) – Prostanthera cineolifera profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~cineolifera
NSW Office of Environment – Threatened Species Profiles – Prostanthera cineolifera profile page https://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10672
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.
Australian Native Plants Society Australia – Prostanthera information page