Distribution: Occurring chiefly east of the Cascades crest and in the Columbia River Gorge in Washington; southern British Columbia to California, east to western Montana, Wyoming, Utah, and Colorado.
Habitat: Dry, open places from the lowlands to middle elevations in the mountains.
Conservation Status: Not of concern
Annual herbs 0.5-3 dm. tall, usually much branched and without a central stem; herbage with spreading, stiff hairs.
Leaves linear or linear-oblong.
Inflorescence of naked spikes, the spikes seldom paired and not noticeably elevated above the mass of the plant; calyx 4-6 mm. long, with stiff, aligned hairs and sticky bristles; corolla white, 1-2 mm. wide; style nearly equaling the nutlets.
Nutlets 4, ovate, 1.2-2.0 mm. long and 0.7-1.1 mm. wide, somewhat granular, covered with small projections.
The similar C. torreyana has smooth nutlets, while the nutlets on C. ambigua are quite rough.