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A spreading shrub to 2 metres tall by 1 metre wide.
It is found on elevated, rocky sites in dry sclerophyll woodland and open forest in New South Wales. It has some disjunct records, but is generally found from the southern Blue Mountains to the Budawang Range and further on the south coast into southern Victoria. There are also some isolated records in central NSW and on the North Coast.
Branches densely covered with more or less spreading hairs. The whole plant is strongly aromatic. Stems square to somewhat rounded.
Prostanthera have simple, opposite and usually odorous leaves (a typical Lamiaceae feature). In this species, leaves are strongly aromatic, to 3 cm long and only 0.6 cm wide, creating a linear to narrow-elliptic shape, mid-green coloured and moderately to densely hairy.
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 dark mauve, to 10 mm long, with petals fused to form a bell-shaped tube. Flowers are produced in the leaf axils, in raceme-like groups or clusters, often leafy at the base. Flowering occurs in spring.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
Not overly common in cultivation and hard to source online.
It could likely be grown on a well-drained soil in full sun to part shade.
Tip prune after flowering to create a denser habit and more flowering the following season.
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 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.
hirtula – Latin – generally meaning “hairy”.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Prostanthera hirtula profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~hirtula
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 http://anpsa.org.au/APOL2007/apr07-1.html
Wikipedia – Prostanthera hirtula profile page https://en.wikipedia.org/wiki/Prostanthera_hirtula