Description from Flora of China
Annuals. Stem 10-45 cm tall, erect or decumbent, not rooting at nodes, with 1-1.7 mm patent nonglandular trichomes and 0.2-0.5 mm patent glandular and nonglandular trichomes. Stipules lanceolate, distinct. Leaves alternate; petiole with 1-1.5 mm patent nonglandular trichomes and 0.2-0.5 mm glandular and nonglandular trichomes; leaf blade 0.9-4 cm, palmately cleft, ratio of main sinus/middle segment length = 0.5-0.75, pilose with appressed nonglandular trichomes; segments 5, obtriangular, 1.5-5 mm wide at base, 3(or 4)-lobed at apex, ratio of second sinus/middle segment length = 0.14-0.25. Cymules solitary, 2-flowered; peduncle 0.5-8 cm. Pedicel 0.5-1.5 cm, with 1-1.8 mm patent nonglandular trichomes and 0.2-0.5 mm patent glandular and nonglandular trichomes; bracteoles lanceolate. Sepals (1-)2.5-5.5(-6) mm, mucro 0.1-0.2 mm, ratio of mucro/sepal length = 0.03-0.1, outside with 1-1.5 mm patent nonglandular trichomes and 0.2-0.5 mm ± patent nonglandular and glandular trichomes, outside glabrous. Petals bright purple, 3-8.5(-10.5) mm, erect to patent, both surfaces glabrous, margin basally ciliate, apex emarginate with a 1-2.5 mm notch. Staminal filaments whitish, lanceolate, glabrous except proximal half with some 0.1-0.2 mm cilia; anthers purplish, 0.7-1.5 mm. Nectaries 5, hemispheric, glabrous. Stigma purplish. Fruit 0.8-1.4 cm, erect when immature; mericarps transversely wrinkled, without a basal callus, glabrous but with a few cilia at base; rostrum 6-11 mm, with a 1-3 mm narrowed apex; stigmatic remains 1-2 mm. Seeds 1.4-1.8 mm. Fl. May, fr. May. 2n = 26.
Although found as a naturalized weed in Taiwan, this species could be found as a native plant near the W boundaries of China, because its natural area includes the W Himalayas. This species also grows as an introduced weed in America and Australia.
Waste places, open habitats, dry grasslands, roadsides; 1800-1900 m. Naturalized in Taiwan [native to Afghanistan, N Africa, W Asia, Europe, Kashmir, Russia].