Armidale District

APS Armidale Fact Sheet - Prostanthera

Text and images by Warren Sheather

P. ovalifolia
Prostanthera ovalifolia
P. striatiflora
Prostanthera striatifolia
P. scutellarioides
Prostanthera scutellarioides
P. lasianthos
Prostanthera lasianthos

The Prostantheras or Mintbushes are members of the Lamiaceae family in company with the culinary mints. They are endemic to Australia occurring nowhere else in the world. At present there are about 120 species. This is rubbery figure as some species are being revised and no doubt new species are lurking in the Australian bush awaiting discovery. The Northern Tablelands is home to ten species.

Prostantheras are dwarf to tall shrubs. The majority have strongly aromatic foliage. Flowers are usually conspicuous and prolific. The palette of flower colours includes white, blue, mauve and pink. Prune Mintbushes after flowering to keep their foliage dense and blooming bounteously.

Mintbushes are usually free from pests and diseases. Some species, during very dry periods, may wilt. A good watering will rejuvenate wilted specimens.

Prostantheras propagate readily from cuttings. Most species will produce roots in a month or less.

The Mintbushes may be divided into two broad categories. There are those that flower in spring and those that bloom in summer. The spring-flowering varieties outnumber the summer-flowering Mintbushes. Regardless of their flowering period many Prostantheras are popular in cultivation.

Prostanthera ovalifolia

The Oval-leaf Mintbush, is probably the most popular species in cultivation.
This medium shrub will reach a height of three metres although judicious pruning will keep plants to a more manageable height. The leaves are lanceolate to broadly ovate, mid-green to dull dark green and aromatic. The flowers are carries in terminal racemes and are mauve or blue-purple. Spring is the flowering period and at this time plants become covered with colourful blooms. There is an interesting form with variegated foliage.

Prostanthera striatiflora

Prostanthera striatiflora

Prostanthera striatiflora, Jockey's Cap Mintbush, comes from the semi-arid regions of New South Wales, South Australia, Northern Territory and Western Australia. The species is common near Broken Hill and the Flinders Ranges.

Prostanthera striatiflora is a medium, upright shrub with narrow, short, aromatic leaves. The flowers are about two centimetres across, white with purple-striped throat. This is another spring-flowering Mintbush and at this time blooms are both prominent and abundant. Their shape is said to resemble the protective helmet worn by jockeys hence the common name. Pruning encourages good foliage cover.

Prostanthera scutellarioides

Prostanthera scutellarioides is a local species that is common in Cathedral Rock National Park where it grows on the margins of wetlands.

Prostanthera scutellarioides is a compact, spreading, dwarf to medium shrub. The leaves are linear, three centimetres long and light green. This is one of the few Mintbushes with virtually no foliage aroma. The deep mauve flowers are reasonably abundant and are carried from September to December. This Mintbush bridges the gap between spring and summer flowering species.

This Mintbush is a very hardy shrub that resists the tendency to wilt during dry periods.

Prostanthera lasianthos

Prostanthera lasianthos is known as the Victorian Christmas Bush and is a medium to tall, variable, strongly aromatic shrub. This Mintbush is widely distributed and is found in all eastern mainland states and Tasmania. On the Northern Tablelands the species is common in New England National Park and Oxley Wild Rivers National Park.

Prostanthera lasianthos has glossy, dark green leaves. The flowers are about 1.5 centimetres long, usually white. There are also pink-flowered forms. The blooms are carried in terminal racemes and are both conspicuous and profuse. The flowering period extends from November to March making this a summer-flowering Mintbush.

Prostanthera lasianthos is a handsome shrub. Container grown plants could be brought indoors and decorated as a genuine Australian Christmas Tree.

This Mintbush is due to be divided into five species.