- herbaceous perennial with prostrate or creeping stems usually 1 foot long or less
- leaves opposite, the pairs unequal in size, deltoid or lanceolate in outline, dark green with white hairs along veins
- flowers of two kinds, the more conspicuous type with a trumpet-shaped white perianth 1-2 inches long
- both flower types are stalkless in leaf axils
- endemic to the northwest corner of the South Texas Plains near Del Rio
- known only from Kinney, Maverick and Val Verde counties
