The Mexican petunia (Ruellia brittoniana) is a fast grower, quickly spreading through self-seeding and rhizomes. Because of their fast growth, these plants are considered invasive.
Light
Mexican petunias love sunshine and will thrive in full sun. They also grow quite well in partially shaded areas, but shade reduces flower production. Plants grown in full sun will have purple stems while those grown in the shade will have green stems.
Soil
These hardy plants can be grown in almost any soil type but do the best in well-draining, rich soil. They prefer neutral to acidic soil pH levels.
Water
Mexican petunias are resilient when it comes to water intake, as they can survive both droughts and floods. During the growing season, it is best to keep the soil evenly moist, watering only once soil begins to dry out. For the winter months, reduce watering until the soil is dry.
Temperature and Humidity
These tough plants are heat and drought-tolerant. They thrive in areas with high humidity and high heat. Mexican petunias do not handle the cold well and are not frost-hardy. Be sure to protect these plants if any cold weather comes your way.
Fertilizer
Fertilizer is unnecessary in most situations.
Propagating Mexican Petunia
These plants can be easily and quickly propagated through stem cuttings and rhizome division. This is best done in the summer. To propagate by cuttings, you will need sharp, clean garden snips, a small pot, well-draining, and rich potting soil: To propagate through rhizome division, you will need a shovel:
How to Grow Mexican Petunias From Seed
Growing Mexican petunias from seed is another easy way of propagating these plants. Here’s how:
Potting and Repotting Mexican Petunias
Mexican petunias can be kept in pots, which is an ideal option for those living in areas with cold winters since the plant can be moved. However, because of its rapid growth rate, Mexican petunias will need to be repotted often. To do this, choose a pot that is at least 2 inches larger than its current pot. Gently dislodge the plant from its pot and set it into the new pot. Fill the pot with well-draining, fertile soil and bury the root system to the same depth it was before. Water thoroughly.
Overwintering
When grown in warm climates with mild winters, Mexican petunias do not require extra winter care. Simply cut back on watering, only when the soil is dried out. If cold temperatures are threatening your area, it is best to move Mexican petunias indoors because they cannot handle cold temperatures.
How to Get Mexican Petunias to Bloom
Mexican petunias are known for their petunia-like, purple, trumpet-shaped flowers that last about a day. Though the blooms themselves die off quickly, Mexican petunias continue to prolifically produce their vibrant blooms for quite some time, usually from early summer to fall. They do not have a strong aroma. To encourage flower production, prune the plant after blooming. Cut down the flowering stems to encourage new growth. Deadhead the spent blooms to make room for future blooms. And be sure to place the Mexican petunia in an area that receives plenty of sunshine, as this will encourage abundant flowering.
Common Problems With Mexican Petunias
Mexican petunias are difficult to kill and can withstand droughts, floods, and high temperatures. Though hardy, gardeners have encountered a few issues with these plants. One of the most common issues is brown leaves.
Brown Leaves
If your plant has brown leaves, it has most likely experienced cold weather and has sustained damage as a result. Move the plant to a warmer area and remove the damaged leaves. The plant will regrow full and lush, if it receives the warmer temperatures it requires.
