There are a number of species called Mexican petunias, or wild petunias, but they aren't related to the usual garden petunia at all. Wild petunia is a lovely perennial. A wildflower native to the Texas, it is almost evergreen, and will bloom in sun or light shade. Violet Ruellia can be found in sandy and clayey soils of the South Texas Plains and Edwards Plateau. It stands approximately 1 to 2 feet in height and is an upright to semi-sprawling plant. The leaves are two to five inches in length and have a toothed edge. The flower has five lobes and can be lavendar to purple in color. Flowering: April-October.