There are around 100 species of evergreen shrubs belonging to this Australian genus. The genus is part of the mint (Lamiaceae) family. Most species have highly scented opposite leaves on squarish stems earning them the common name of ‘mint bush’. The tubular flowers are usually two-lipped with three lobes appearing on the lower lip. They are mostly short-lived under cultivation but make up for it by growing quickly and flowering well while still quite small.
One of the highly decorative shrubs of this genus is Prostanthera magnifica, also known as the magnificent mint bush or splendid mint bush. It is native to the semi-arid regions of southern Western Australia. It has leathery elliptic leaves to 30mm. The pale mauve or pink flowers are very showy with large contrasting calyces, and are borne in leafy, spike-like clusters.
Another attractive example is Prostanthera ‘Poorinda Ballerina’. This upright hybrid shrub has aromatic foliage which may have olive tints. The flowers are white with mauve spotting and appear from spring to early summer.
‘Variegata’ is a cultivar of Prostanthera ovalifolia (purple mint bush). The aromatic leaves have yellow edges. Masses of purple or mauve flowers appear in spring. The flowers have darker spotted throats.
Prostanthera aspalathoides has the common name of scarlet mint-bush. It grows to 0.6 metres high with a similar spread and is native to the drier regions of south-east Australia. It has fine, strongly aromatic foliage. The tubular flowers of scarlet, deep pink, orange or yellow are produced over a long period but mainly from September to February. Unlike many of the Prostanthera species which prefer shade and moisture, it is best in a warm, well-drained position. It responds well to tip pruning and is attractive to birds, relying on its feathered friends for pollination of the flowers.
The Monkey Mint-bush or Prostanthera monticola is a dense, bushy plant with dark green leaves. It produces tubular flowers to 2-3cm long mainly from November to February. The striking flowers are an unusual shade of green streaked with purple. It responds well to pruning, is frost tolerant and a favourite with birds.
Prostanthera lasianthos has the common name of Victorian Christmas Bush. This upright shrub may grow to 6 metres and has aromatic, dark green leaves to about 10cm long with toothed margins. It produces a good display of tubular flowers from November through to January. The flowers are commonly white to pale mauve with purple and orange markings in the throat. Pale mauve and pink forms are also available. This is an ideal choice for shaded positions. It is a quick growing species and can be pruned to promote bushy growth.
These plants require a warm climate and really good drainage. They will thrive in a sheltered position. Most will appreciate being planted under cover of trees with open, light foliage. Tip prune while young and after flowering to promote a compact bushy growth and good shape.
