Distribution: East of the Cascades crest in Washington; widely distributed throughout much of North America.
Habitat: Noxious weed of sandy soils and roadsides.
Conservation Status: Not of concern
Stiff-hairy, prostrate annual, forming mats 3-10 dm. broad.
Leaves opposite, pinnate; leaflets 4-8 pairs, obliquely oblong-ovate, 5-15 mm. long; stipules 1-2 mm. long.
Flowers solitary on short, axillary peduncles; sepals 5; petals 5, yellow, 3-5 mm. long, attached at the edge of a 10-lobed disk; stamens 10, borne within the disk; style 1, stigma 5-lobed.
Fruit depressed, deeply 5-lobed, separating at maturity into 5 hard, 2-spined segments, the spines 2-6 mm. long, with numerous smaller spines that form a broad, dorsal, longitudinal row.