About Prostanthera ovalifolia R.Br.
Prostanthera ovalifolia, common name oval-leaf mintbush, is an erect, spreading to dense shrub that usually reaches a height of 1 to 4 meters (3 feet 3 inches to 13 feet 1 inch). Its stems are square in cross-section and moderately covered in hairs. The leaves are egg-shaped, with a lighter green color on the lower leaf surface. They measure 5 to 50 millimeters long, 3 to 12 millimeters wide, and grow from a 1 to 6 millimeter long petiole.
Flowers grow in groups at the ends of branchlets. Each flower has 1 to 2 millimeter long, 0.2 to 0.3 millimeter wide bracteoles at its base, and these bracteoles fall off as the flower develops. The sepals are 2 to 3.5 millimeters long, and form a 1 to 2.5 millimeter long tube with two lobes; the lower lobe measures 0.5 to 1.5 millimeters long. The petals are colored mauve to deep blue-purple, are fused together to form a 6 to 18 millimeter long tube, and flowering takes place between August and November.
Oval-leaf mintbush is widespread in forest habitats growing on sandstone in south-eastern Queensland and eastern New South Wales, and it is also sporadically naturalised in the eastern half of Victoria. This mintbush is widely cultivated as a garden shrub, where it typically reaches a height of around 2.5 meters (8 feet 2 inches). It grows best in well-drained soil with some protection from direct summer sun, and should be pruned back by approximately one third to retain its bushy shape.
