Polanisia dodecandra subsp. riograndensis
SouthW. Naturalist 14: 116, fig. 1[top]. 1969.
Leaflets: blade apex rounded. Inflorescence bracts ovate to orbiculate. Petals pink, rose, or purple, (6–) 8–14 (–17) mm. Stamens (6–) 7–17 mm, equaling or slightly longer than petals. Seeds tuberculate-rugose. 2n = 20.
Phenology: Flowering spring–fall.
Habitat: River banks, coastal dunes, open woodlands, mesquite, and semi-desert
Elevation: 0-100 m
Tex., Mexico (Nuevo León), Mexico (Tamaulipas)
Subspecies riograndensis is found along the lower Rio Grande in Texas and adjacent Mexico.