Prostanthera rotundifolia - Mint Bush

Prostanthera rotundifolia, sometimes called Australian Mint due to its origins or Tree Mint, is a frost-tolerant shrub, which is well adapted to dry and poor soils. It forms a rounded but light weight bush with small leaves that become greyer when the soil is dry.  It is covered in spring with a multitude of small tubular flowers, gathered in violet clusters. Endowed with a somewhat indefinable charm, it deserves to be seen and smelled up close and will undoubtedly impress the curious visitor, touched by its sometimes fragile appearance despite its undemanding resilience. To succeed in mild climates, remember that it does not like water in summer, but appreciates partial shade, especially in hot climates.  Do not place it on the lawn and avoid regular watering which could cause it to perish as much as a severe frost!

Prostanthera rotundifolia, meaning round-leaved, is native to eastern Australia, New South Wales, the state of Victoria, and Tasmania. It is a plant that thrives in well-drained and dry soil, and also does well in oceanic climates, as seen by beautiful specimens planted in sheltered positions in certain coastal gardens. This highly branched shrub has a rounded, slightly spreading habit, supported by slender, hairy, square-sectioned branches. Its growth is quite fast in moist soil, a little slower in dry and poor soil. The lifespan of this plant is about 6 to 8 years, including in its native lands. An adult specimen will reach an average height of 2m (7ft) with a spread of 1.5m (5ft). Its evergreen foliage is composed of small, simple, opposite, rounded to ovate, dentate leaves, measuring 1cm (1in) to 1.5cm (1in) in length. They are dark green in colour, but covered in white hairs that give them a more greyish hue, especially in hot and dry climates. When crushed, they emit a pleasant menthol scent. Flowering takes place in April-May. The small bell-shaped flowers with 5 lobes are grouped in clusters measuring 5 to 7cm (2 to 3in) in length. They emerge from the axils of reduced leaves, on lateral branches. The flower size varies between 0.5 and 1cm (1in) in length and their colours vary between light violet and purple. The fruit is like a small almond.

Australian Mint is elegant, subtle for much of the year, and delightful in spring. The shrub is tolerant in terms of soil type, resistant to drought, and not afraid of salt spray. Its only enemy is the cold, which can make it disappear when temperatutres fall below -5°C (23°F) if the soil is not sufficiently well-drained. It requires little maintenance and even prefers to be forgotten from time to time, especially in summer. A light annual pruning after flowering is sufficient. It will easily thrive in gardens along the Atlantic or Mediterranean coast. It forms beautiful borders, along a wall or in a well-drained bed, in the company of evergreen Melaleuca, Gomphostigma, Leptospermum, and lower growing Ceanothus (Italian Skies, Concha, Victoria). Mimosa, Leucophyllum, Raphiolepis, Oleander, Callistemon, or Grevillea can also accompany it in a dry or coastal garden. The choice is vast, it's all a matter of taste. Container cultivation can allow the shrub to overwinter in a cold greenhouse or a very bright and minimally heated conservatory in very cold regions.