Mexican Petunia Plant Care

Mexican Petunia (Ruellia brittoniana) belongs to the Acanthaceae family within the Ruellia genus. Mexican Petunia is native to Mexico, the Caribbean, and South America. Mexican Petunia is also known as Britton's Wild Petunia, Water Ruellia.

Mexican Petunia displays a low rosette, spreading ground cover growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Mexican Petunia produces tubular flowers in shades of purple, pink, or white.

Water a young or newly planted Mexican Petunia every 7–10 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.

Mexican Petunia thrives in bright indirect light. Avoid placing Mexican Petunia in direct, harsh sunlight for extended periods, as this can scorch the foliage.

Ruellia brittoniana tolerates temperatures of 65–85°F. Mexican Petunia prefers humidity levels of 50–70%. A pebble tray or humidifier helps maintain adequate moisture around the plant.

Well-draining, fertile soil with added organic matter like compost or peat moss. Good drainage is essential for Mexican Petunia to prevent waterlogging, which leads to root rot and fungal issues.

Feed Mexican Petunia every month 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 bright indirect light and well-draining, fertile soil with added organic matter like compost or peat moss. Avoid low spots where water collects after rain.

Mexican Petunia is suited to USDA Zone 8a – 11b.

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.

Mexican Petunia 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 Mexican Petunia 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.

Mexican Petunia is hardy down to USDA zone 8a, so once established it can stay outdoors through winter in that zone and warmer ones.

Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.

Young and container-grown shrubs need extra protection: roots in a pot freeze much more easily than roots in the ground.

Mexican Petunia can be propagated through seeds, division of clumps, stem cuttings.

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

Mexican Petunia 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.

Mexican Petunia grows outdoors in USDA Zone 8a – 11b. It survives winters down to planting zone 8a. Mexican Petunia is native to Mexico, the Caribbean, and South America.