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Care of Mexican Petunias

By: Bridget Kelly

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07 January, 2011

The Mexican petunia (Ruellia rudiflora) is a lovely addition to the garden but has a tendency to take over once it becomes established. It readily self-seeds and has been classified as an invasive plant in the state of Florida. A perennial, the Mexican petunia grows to 3 feet in height and bears light purple flowers. It is especially low-maintenance, making it great for beginners. Mexican petunias are hardy to U.S. Department of Agriculture Hardiness zones 8 through 10 and requires a full-sun location and a warm climate.

Water the Mexican petunia only when the soil is dry. Water the soil to a depth of 10 inches and allow it to dry before watering again.

The Mexican petunia (Ruellia rudiflora) is a lovely addition to the garden but has a tendency to take over once it becomes established.

Fertilize the petunia with a 10-10-10 formula in early spring. Use the amount specified on the fertilizer label and apply it to the soil around the plant.

Prune back the stems to half their length after the flowering period to prompt the Mexican petunia to re-bloom.

Hand-pull new seedlings to keep the Mexican petunia from invading the rest of the garden. Wait until they produce flowers if you are unsure if what you are finding is actually a Mexican petunia seedling. One way to identify the seedling is by the leaves. Although there are several Mexican petunia cultivars, the shape of their leaves is generally the same: they are longer than they are wide and resemble the adult's leaves, only smaller.

Fertilize the petunia with a 10-10-10 formula in early spring.
Prune back the stems to half their length after the flowering period to prompt the Mexican petunia to re-bloom.

Long Does It Take Mexican Petunias To Grow?

Mexican petunia, also called desert petunia, establishes itself quickly when you start with a nursery-grown seedling or young plant. It generally produces groups of strong, semi-woody stalks about 3 feet tall that bear attractive foliage and produce flowers within a month or two. Mexican petunia produces seeds that germinate readily and grow into plants identical to the parent. New seedlings grow well if their soil is kept moist, but they may only produce a few late-season flowers during the first year. Although it grows best in full sun, it can also handle some shade, but this may reduce flowering. You can grow Mexican petunia as a potted plant, either outdoors or indoors in a bright, sunny spot.