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A shrub to 2.5 metres tall, spreading to 2 metres wide; aromatic.
It grows naturally in NSW and Queensland in disjunct patches, possibly as far south as Nowra in NSW; very commonly in western Sydney where it grows in Cooks River Castlereagh Ironbark Forest; as far west as Orange – Dubbo and extending up the coast, tablelands and western slopes, to as far north as Biggenden in Queensland.
Prostanthera have simple, opposite and usually odorous leaves. In this species, the leaves are linear, pale to mid-green, up to 25 mm long and to 2 mm wide, sometimes curved. Unlike most mint bushes the foliage of this species, has virtually no perfume.
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 about one centimetre long, pale to deep mauve and form leafy racemes during the spring/summer flowering period. Sporadic flowering may occur at other times.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
From Jeff Howes:
I have been growing Prostanthera scutellaroides for many years, in my garden in the northern Sydney suburb of Westleigh. For me, it is a dense shrub which grows to about 1.8 metres high with a similar spread and produces masses of purple/deep lilac flowers in spring. During the peak blooming season, plants are generous with their floral contributions. Light pruning after flowering is beneficial.
My plants are growing in a thin layer of topsoil over a clay sub soil in a well drained position and receive some additional watering in dry spells. They are very hardy and grow best in a position that has good drainage and protection from afternoon sun.
The only maintenance required is to give them a good prune after each flowering to keep them compact in shape and promote better flowering next season. I remove about a third of last season’s growth.
This is a plant that will grow well in shade, I made the mistake of planting one in a position that receives morning dappled shade and full afternoon sun. This caused new sappy growth to wilt. When the sun goes off the plant it recovers with no harmful effects and it still flowers spectacularly. Some Prostanthea have a short flowering time. However I find that this species flowers for me for well over a month in early Spring.
Prosthanthea are interesting plants. After several weeks of hot dry weather they curl their leaf edges, start to drop their leaves and look like they are going to die. This happened to me when I went on holidays over summer. When I got home, I thought I had lost the plant. I gave it a good, deep watering and to my amazement the next day it started to recover and over the next few weeks it grew back most its lost leaves and looked as if nothing had happened to it. They clearly have the ability to go into a state of ‘suspended animation’ until rain arrives and then spring back into life. Having said that, I will not try that out on one my other Prosthanthea any time soon.
Prostanthera scutellaroides is stunning in flower as the purple/deep lilac flowers contrast the small dark green aromatic leaves so well – a great plant for any shady garden.
From Warren and Gloria Sheather:
Prostanthera scutellarioides is a very hardy and colourful mint bush. Unlike many of its relatives this species is resistant to wilting during dry spells. Frosts do not bother our specimens.
The Australian Defence Industries (ADI) site at St Marys, west of Sydney, is home to an area of the sadly diminished Cumberland Woodland. Whilst working there, many years ago, interesting lunchtime walks used to be taken exploring the local flora. Prostanthera scutellarioides was common in the woodland. Cutting material was collected and we grew Prostanthera scutellarioides in our Blue Mountain’s garden.
Skip forward many years and we are living in the Armidale area. We heard rumours that Prostanthera scutellarioides grew along the Waterfall Way, east of Armidale on the banks of a number of creeks. We eventually found the mint bush in a number of sites and it is now included in our cold climate garden collection.
From Dan Clarke: I still see the plants Warren refers to above, when monitoring threatened flora in the Western Sydney nature reserves every autumn and winter.
This mint bush propagates readily 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.
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.
scutellarioides – Latin – resembling the genus Scutellaria, another genus in the Lamiaceae family, for which there are natives and weeds in Australia.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Prostanthera scutellarioides profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~scutellarioides
Australian Native Plants Society Australia – Prostanthera scutellarioides profile page https://anpsa.org.au/plant_profiles/prostanthera-scutellarioides/
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.