Prostanthera aspalathoides is a dwarf, erect shrub, reaching a height of 1 metre.
It grows in the central areas of NSW, around Griffith (and to the east) and north to Cobar, as well as east of Mildura. It grows in north-western Victoria and the south-east of South Australia, west to about Lock and Kimba-areas.
It grows on red sandy loams in open dry scleorphyll woodland and shrubland, usually on sandstone substrate with ironstone.
Prostanthera have simple, opposite and usually odorous leaves. In this species, leaves are small, to 6 mm long and 1 mm wide; crowded, deep green and, typically of most mintbushes, very aromatic. The margins can often curve down (recurved).
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, flowers are unusually extendedly tubular, to 2 cm long, and can be red to pink-red, to orange and even yellow (which is rarer); produced solitarily in leaf axils.
Fruits are mericarps (can be called nutlets). Four are produced produced at the base of the calyx.
Author’s notes: Prostanthera aspalathoides is an attractive small shrub. Plants look a trifle delicate but in our harsh climate this species has proved to be drought and frost resistant.
The plant illustrated is our yellow flowered form. There is also a specimen with red flowers in our collection. With both forms blooms are both conspicuous and prolific in spring.
This attractive could be grown in native cottage gardens and rockeries.
It can be difficult to grow and it is recommended to purchase grafted forms which are usually plugged onto Prostanthera nivea. It is not suited to tropical climates or high humidity.
Prostanthera aspalathoides has flowers that are different in shape to “conventional” mintbush blooms. The Prostantheras are divided into two sections. Most species are in the Prostanthera section and they have regularly shaped flowers including the well known Prostanthera ovalifolia and Prostanthera rotundifolia. Klanderia is the other section that has laterally compressed, tubular flowers. Prostanthera aspalathoides is a representative of the Klanderia section. Another representative is Prostanthera serpyllifolia. Species in sction Klanderia are more likely pollinated by birds rather than insects.
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.
Propagation from cuttings is fast with multiple roots developing.
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.
The species was described by botanist Allan Cunningham in 1834 based on plant material collected in the vicinity of the Lachlan River in NSW.
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.
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.
aspalathoides – Latin – resembling the genus Aspalathus – a group of peas from South Africa.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Prostanthera aspalathoides profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~aspalathoides
Australian National Herbarium – Prostanthera aspalathoides profile page https://www.anbg.gov.au/gnp/interns-2010/prostanthera-aspalathoides.html
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.