Prostanthera spp.
mint bush
Overview
Prostanthera is a genus of about 100 species of aromatic evergreen shrubs in the mint family (Lamiaceae), all native to Australia. Plants range from prostrate forms under 12 inches (30 cm) tall to upright shrubs reaching 13 feet (4 m), though most cultivated species grow 3-6 feet (0.9-1.8 m). The square stems carry opposite leaves dotted with oil glands that release a minty scent when crushed. Flowers are tubular and two-lipped, 0.3-0.6 inch (8-15 mm) long, in shades of purple, mauve, violet, blue, pink, and white, borne in clusters along the upper stems. Species such as P. ovalifolia and P. rotundifolia flower heavily in spring, while P. cuneata tolerates colder, higher-elevation sites. The genus needs sharp drainage and is intolerant of prolonged wet soil, which can cause sudden collapse from root rot. Most species are frost-sensitive, suited to USDA zones 9-11, though a few withstand light frost. Many plants are short-lived, declining after 5-10 years. The aromatic foliage is generally passed over by browsing mammals, and the nectar-rich flowers draw native bees and other pollinators.
Native Range
All Prostanthera species are endemic to Australia, where they grow in habitats ranging from coastal heath and dry sclerophyll forest to subalpine slopes and rocky outcrops. The genus is most diverse in the south-east, including New South Wales, Victoria, and Tasmania, with further species in Western Australia and Queensland.Suggested Uses
Used in low-water and native gardens, mixed shrub borders, and coastal plantings in mild climates. Compact species are grown in containers and rockeries, while larger forms serve as informal flowering hedges or screens. The aromatic foliage is also grown beside paths, where brushing releases the scent.How to Identify
Appearance
Size & Dimensions
Height6" - 13'
Width/Spread1'6" - 10'
Reaches mature size in approximately 3 years
Colors
Bloom Information
Most species flower in spring, roughly April to June in the Northern Hemisphere, with bloom lasting 4-6 weeks. Some produce a lighter second flush in autumn. Flowering is heaviest in full sun with free-draining soil.
Detailed Descriptions
Flower Description
purple, mauve, violet, blue, pink, or whiteFoliage Description
green to grey-greenGrowing Conditions
Sun Requirements
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Grow Prostanthera in full sun to light shade in sharply drained soil, as waterlogging is the most common cause of plant loss. Sandy or gravelly loams with a slightly acidic to neutral pH of 5.5-7.0 suit the genus. Water regularly during establishment, then reduce to occasional deep watering once plants are settled, as most species tolerate dry spells. Feed sparingly with a low-phosphorus fertiliser, as many Australian natives are sensitive to high phosphorus. In cold-winter regions, frost-tender species are grown in containers that can be moved under cover. Aphids and root rot are the main problems, both worsened by rich or wet soil.Pruning
Prune Prostanthera lightly immediately after flowering to maintain a compact shape, removing up to one-third of the current season growth. Cutting into old, leafless wood often fails to resprout, so hard renovation is limited. Tip-pinching young plants encourages denser branching.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
late springsummer
Container Growing
Suitable for container growing
Minimum container size: 5 gallons