Life cycle
Winter annual, less than 12-in. tall; noticeable in spring for pink to purple flowers.
Growth habit
Square stems; leaves opposite, scalloped, and rounded; lower leaves with petioles, upper leaves half encircling the stem; pinkish-purple, lipped flowers in whorls in the axils of upper leaves; fibrous root system that does not creep along the ground.
Reproduction
Seed germinating in early fall or early spring.
Conditions that favor growth
Mowing the lawn too short and improper fertilization.