Houstonia rubra

Houstonia rubra, the red bluet, is a plant species in the Rubiaceae. It is a small herb with white to pink to red to reddish-purple flowers, native to the southwestern United States and northern and central Mexico: Coahuila, Nuevo León, Hidalgo, Zacatecas, Guanajuato, Puebla, Sonora, Durango, Chihuahua, Arizona, New Mexico, southeastern Utah and western Texas.