Prostanthera ‘Ragged Robin’ is a short to medium shrub, to 3 metres tall by 2 metres or more wide, with an upright growth habit. It is a hybrid from P. ovalifolia and P. staurophylla.
Prostanthera have simple, opposite and usually odorous leaves. In this cultivar, strongly aromatic leaves are about 2 cm long by 1 cm wide with distinctive lobing almost forming a cross-shaped leaf; grey-green to pale green.
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 cultivars, flowers are 1.5 centimetres long, mauve-blue and carried in the upper leaf axils during late spring and early summer. Blooms are conspicuous and profuse.
Prostanthera ‘Ragged Robin’ would be both an aromatic and colourful addition to a native garden bed.
Not a lot of information is available online regarding this cultivar but it has been in cultivation for a while. The literature cited below has it listed. Best grown on a well-draining soil in semi-shade. Check with local native nurseries for availability.
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.
Propagate from cuttings to retain true-to-type characteristics of the cultivar.
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.
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.
‘Ragged Robin’ – exact meaning of cultivar name is not known. It may refer to the shape of the leaves. (Please note: there are other exotic plants which go by the common name of Ragged Robin).
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.