Prostanthera howelliae

Family: Lamiaceae

An erect or spreading shrub growing to a height and spread of 0.3 to 1.5 metres.

It is found naturally in dry sclerophyll woodland and shrubland, often in gravelly or sandy soil, in the eastern half of New South Wales from the central and northern coastal subdivisions through to the tablelands, slopes and the western plains, and into Queensland and Victoria.

The whole plant is aromatic and stems are somewhat square. Branches are densely covered with short hairs.

Leaves are in opposite pairs (rarely in 3-leaf whorls), mostly linear-elliptic to 1 cm long and to 0.2 cm wide, mid-green coloured, often with a maroon tinge, margins are entire and curved down with the tips blunt.

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, the flowers are pink to purple-mauve, with petals forming a bell-shaped tube, with dark red, maroon or purple dots in the throat, to 10 mm long. Flowers are arranged singularly at the base of paired leaves, forming leafy clusters and occur in spring.

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

In the garden

This species is available from some online nurseries and would be a nice addition to any garden. Grow in a sunny to partially shaded position and provide good soil drainage. Sandy is likely the most optimal. Tip prune after flowering to promote density and flowering the next 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

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 hybridising when in cultivation.

Some 80% of mints contain aromatic oils within their leaves with oil of cineol being a major component. Prostanthera sieberi, P. 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 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.

howelliae – honours Mrs T.J. Howell, after whom botanist William Blakely (1875 – 1941) named the species, stating that Mrs Howell had ‘for a number of years… taken a keen interest in the native flora’.

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_howelliae

https://apps.lucidcentral.org/plants_se_nsw/text/entities/prostanthera_howelliae.htm

By Jeff Howes, edited by Dan Clarke