This member of the Acanthaceae family is one I have seen only three times in ten years. Ancanthaceae is large diverse family that is world-wide in distribution with the majority of its species being found in the tropical regions.
There are 36 species of Ruellia in North America and 24 of them are found in Texas. Ruellia humilis, the Fringeleaf Wild Petunia is easily distinguished in the field by the fringes of hair-like projections on its leaf margins and on the underside of its leaves along the veins. Its leaves are short-stalked and lanceolate in shape. The leaves are arranged opposite one another along the stems. Its flowers are trumpet-shaped, pale lavender to dark blue, and form 5 lobes at the mouth. It can be found in dry, sandy or clay soils of grasslands or open forests in most of Texas.