A couple of years ago, I received a call in late summer from a new gardener asking about a plant he had seen at a local golf course. I was interested because he described it as a blue azalea. I visited the golf course and toured until I found the plant. It wasn’t a blue azalea after all, but the familiar Mexican petunia.

Known botanically as Ruellia, Mexican petunia is a flowering plant that really shows off in the hot, dry conditions of summer. The brilliant purple, trumpet-shaped flowers point up. Stems can reach up to 4 feet tall and, when massed, really make a purple statement.

Mexican petunia flowers best in the full sun. Each flower opens for only a single day, and the plant produces what seems like an endless number of blooms. Many gardeners like Mexican petunia because it is easy to grow and enjoy.

The main problem with the species is that Mexican petunia can be aggressive. It spreads by underground rhizomes and readily reseeds, which means it can become a weedy problem. But gardeners now have new ways to enjoy the gorgeous purple blooms of Mexican petunia.

Plant breeders have selected dwarf varieties, Ruellia brittoniana, that are not as aggressive. A variety I have been trying is called Katie Dwarf, and it is perfect for the container I have it growing in. It has stayed about 6 inches tall all summer without any trimming. The flowering has been nonstop as long as the plant stays well-watered.

Like its aggressive cousin, Katie Dwarf is self-cleaning and doesn’t have to be deadheaded. Perhaps its best feature is the fact that it is perennial, so my wife and I will enjoy this plant every year.

Another variety I started growing last year is called Ragin’ Cajun, or Ruellia elegans. Native to South America, the plant is covered with brilliant scarlet flowers. The regula species can reach 4 feet tall, but Ragin’ Cajun stays small at about 12 inches and is perfect for growing in a container. The flowers are held upright on thin stems that move with the slightest breeze.

Ragin’ Cajun over-wintered for me on the coast, but it is not reliable farther north. This plant is also called false petunia or hardy petunia, and it should be considered a tender perennial. Like other Ruellia, Ragin’ Cajun tolerates a variety of soil conditions.

Whichever type of Mexican petunia you decide to grow in your garden, remember to plant it in full sun and maintain consistent moisture. Do this to ensure you will get the best flowering performance, and your plant will make a colorful exclamation point in your landscape.