Rhomboid Mint Bush Plant Care

Rhomboid Mint Bush (Prostanthera rhombea) belongs to the Lamiaceae family within the Prostanthera genus. Rhomboid Mint Bush is native to disjunct areas of south-eastern Australia.

Rhomboid Mint Bush displays an upright, bushy shrub growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Rhomboid Mint Bush produces small, tubular flowers in shades of purple, pink, or white.

Leaf size: approximately 2 inches.

Water a young or newly planted Rhomboid Mint Bush every 7–14 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established shrubs mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

Rhomboid Mint Bush thrives in full sun to partial shade.

Prostanthera rhombea tolerates temperatures of 50–80°F. Rhomboid Mint Bush prefers humidity levels of 40–70%.

Well-draining, slightly acidic soil with added organic matter like compost or peat moss. Good drainage is essential for Rhomboid Mint Bush to prevent waterlogging, which leads to root rot and fungal issues.

Feed Rhomboid Mint Bush every 6 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established shrubs in good soil often need little extra feeding, so let weak growth or pale foliage guide you.

Stop feeding by late summer so new growth can harden before winter.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Choose a spot with full sun to partial shade and well-draining, slightly acidic soil with added organic matter like compost or peat moss. Avoid low spots where water collects after rain.

Rhomboid Mint Bush is suited to USDA Zone 12a.

Plant container-grown or balled-and-burlapped shrubs in spring or early autumn, setting the root flare at soil level, and water well after planting.

Rhomboid Mint Bush can spread to about 2 ft (0.6 m) and reach about 3 ft (1 m) tall. Space plants about 2 ft (0.6 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the plant spacing calculator.

Prune Rhomboid Mint Bush while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.

If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the shrub in one year.

Rhomboid Mint Bush is frost-tender (hardy to USDA zone 12). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Rhomboid Mint Bush can be propagated through softwood cuttings, semi-hardwood cuttings.

See all plants toxic to cats and plants toxic to dogs.

Rhomboid Mint Bush is susceptible to aphids, spider mites, whiteflies. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.

Rhomboid Mint Bush grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Rhomboid Mint Bush is native to disjunct areas of south-eastern Australia. In cooler regions, grow Rhomboid Mint Bush as a houseplant or bring it indoors before the first frost.