POTM: Native Mint Bush

Plant of the month for February

 Prostanthera rotundifolia

Australia is home to thousands of different trees, bushes and flowers. Many of these species are hardy to survive in our Illawarra climate. Australia offers moist coastal areas, dry arid locations, and wet rain-forests and mountain cliffs, each with different growing conditions.

One of my favourite fragrance plants of all is the native mint bush.

Prostanthera is a genus of about 90 species which occur only in Australia. They are known generally as "mint bushes" because of the aromatic foliage of many species. 

As a member of the Lamiaceae, Prostanthera is related to a number of culinary herbs such as mint, thyme, oregano and sage.

Prostanthera rotundifolia may reach 1.5m high by a similar spread. Flowers are generally purple in colour and are prolific in spring. Pink flowered forms are sometimes seen. It is one of the hardier members of the genus, is quick growing and should be pruned back annually by about one third if a bushy shape is to be retained. 

Like most prostantheras it prefers a well-drained, moist position with some shelter from direct summer sun. Under dry conditions it will wilt noticeably but quickly recovers when watered. It is a good "indicator" of when watering is required in a garden generally.

Prostantheras respond to well to annual fertilizing after flowering and are not as sensitive as some other Australian plants to phosphorus.

Propagation is easy from cuttings but seed can be slow to germinate. In areas where the root-rot fungus Phytophthora cinnamomi is a problem, grafting onto the related Westringia fruticosa is recommended.