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Prostanthera saxicola is a variable prostrate to erect shrub that may reach a height of 2 metres but usually smaller.
It has a large natural range, in disjunct patches, growing through NSW on the coast, tablelands and western slopes subdivisions; from as far south as Narooma and towards Cooma; extending north with many records west of Milton and Ulladulla in Morton National Park; also growing on the south of Jervis Bay; scattered through the Sydney area, the Blue Mountains and further north; then occurring around Coonabarabran and from generally around Tingha, north over the border to Stanthorpe in Queensland. It also grows in central Victoria, scattered between Bairnsdale and Horsham.
It typically grows in heath and dry sclerophyll woodland and forest, on a range of substrates including sandy and heavier soils.
Prostanthera have simple, opposite and usually odorous leaves. In this species, leaves are crowded to scattered, linear to elliptic, up to 15 millimetres long by 6 mm wide, aromatic and covered with white hairs.
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 produced in leaf axils and solitary, white to mauve and appear from July to February.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
Four varieties are currently recognised in NSW:
This species is known to be cultivated.
It is reported that var. montana grows to 30 cm high and makes a good groundcover where as var. bracteolata may grow erectly.
There is a cultivar called ‘Pigeon Blue’ (a prostrate form of var. saxicola) which could be grown as a colourful and aromatic ground cover in native garden beds.
It is reported to be a reliable species for gardens. Plant in a semi-shaded spot with good drainage. A sandy soil may work best.
Check local native nurseries for availability.
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.
Propagate from cuttings.
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.
(This Editor once undertook a search for this species along Heathcote Rd in the Lucas Heights area in Sydney with other APS Members and NSW botanists, around 2019. Seedlings were found clustered together after a fire, to only 10 cm tall).
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.
saxicola – Latin – from saxum meaning ‘rock’ and incola meaning ‘resident’ – referring to the rocky habitat this species is often found on.
(var. bracteolata – Latin – “bearing bracteoles” – referring to the longer bracteoles on this variety).
(var. montana – Latin – referring to “mountain-dweller” – possibly referring to this variety inhabiting the Blue Mountains)
(var. major – Latin – usually meaning “larger” – referring possibly to the larger leaves of this variety).
This species is not known to be at risk of eztinction in the wild.
NSW Flora Online (PlantNET) – Prostanthera saxicola profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~saxicola
Plants of South Eastern New South Wales – Prostanthera saxicola profile page https://apps.lucidcentral.org/plants_se_nsw/text/entities/prostanthera_saxicola.htm
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.