Prostanthera violacea

Violet mint-bush

Family: Lamiaceae

Is a slender, strongly aromatic shrub, to 2 metres tall, growing in dry sclerophyll forests including rainforest, often in gullies or near watercourses, mainly on the coast of New South Wales and mostly south from around Newcastle, with some disjunct records further north and in Victoria and Queensland.

Branches are densely hairy.

Leaves are in opposite pairs (rarely in 3-leaf whorls), more or less round but usually appear egg-shaped or ovate because the edges are rolled under, to 6 mm long and 1 mm wide.

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 solitary in the leaf axils. The petals are to 7 to 8 mm long, fused for most of their length, mauve to blue, the tip often whitish; Flowering occurs in Spring.

Fruits – 4 tiny nutlets (mericarps) produced at the base of the calyx.

In the garden

In a garden situation this species needs perfect drainage and near to full sun to grow well. Mulch well. Prune after flowering.

Plants are available from some online nurseries and may be available from retail nurseries.

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

Propagation

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.

Other information

There are approximately 100 species, endemic to Australia. They occur in all States.

This genus is currently under revision, and several species complexes are unresolved. Natural hybrids occur between several species and most species appear to be capable of hybridizing when in cultivation.

Some 80% of mints contain aromatic oils within their leaves with oil of cineol being a major component. Prostanthera sieberiP. incisa and P. staurophylla are quite pleasantly overpowering due to their exudates when crushed.

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.

Most Prostanthera species 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.

violacea – Latin meaning “violet-coloured” referring to the colour of the flowers.

https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=gn&name=Prostanthera
http://anpsa.org.au/APOL2007/apr07-1.html
https://en.wikipedia.org/wiki/Prostanthera_violacea

By Jeff Howes