The widely adaptable dwarf Mexican petunia (Ruellia brittoniana) has been named a Texas Superstar® by Texas A&M University.
“I first observed Ruellia growing in the neglected space between a sidewalk and the street in San Antonio,” said Dr. Wayne Mackay, Texas Agricultural Experiment Station horticulture researcher at Texas A&M Dallas.
“The tall upright, dark green plants with lance–shaped leaves and bright purple, tubular flowers were in full bloom in the hottest part of the summer and showing no signs of being neglected, although they were certainly in a tough location.”
Mexican petunias are very adaptable and will tolerate wet and dry soils. They prefer full sun but will tolerate shade; however, since flowering is light–related, the plants will flower less in shade.
“Mexican petunias and their cultivars are perennial and will remain green under conditions of light frost. However, the foliage will die when a severe frost occurs, and the plant will go dormant until spring,” said Mackay.
Although Mexican petunias are drought–tolerant once established, they perform best with regular irrigation during droughts and with regular feeding of high phosphorus fertilizers. They are disease– and insect–resistant and only rarely bothered by snails and caterpillars.
“One limitation of the species is that it can be aggressive in well–cared–for situations, spreading by both seed and rhizomes which can be a major limitation for use in rich garden soil, so the introduction of a dwarf Ruellia was a great step forward,” said Mackay.
“The dwarf, less–aggressive version of the species is Katie dwarf Ruellia (sometimes called Nolan's dwarf). About 6 inches in height, it works nicely in an informal front–of–the–border grouping or as a groundcover in narrow spaces,” said Mackay. “Katie needs no deadheading, and will continue to flower all season long, and is just as tough as its species parent, able to grow in hot, dry neglected spots.”
In good soil, the plant will reseed true, but is not as invasive as others in the species. Recently, a dwarf pink version of Katie called Bonita™ was patented and introduced by Color Spot Nurseries.
The Texas Superstar® effort is one of Texas A&M University's most innovative and successful horticultural research and Extension programs.
“This cooperative program combines the expertise of university and industry leaders in the identification of superior landscape plants for Texas and their subsequent introduction in the marketplace,” said Mackay.
To identify such plants, the Agriculture Program at Texas A&M conducts extensive horticultural field trials, during which the plants are never sprayed with any pesticide.