Mat-forming winter annual with numerous branched stems. Leaves opposite, smooth, oval to broadly elliptic in shape. Upper leaves without petiole; lower leaves with sparsely hairy long petiole. Stems with vertical lines of hairs. Flowers in small clusters at ends of stems, white, with five deeply notched petals. Reproduces by seed. Located throughout North America except for the Rocky Mountains. Also found in Mexico, Central and South America, Hawaii, Asia, Africa and Europe.