Plants usually stoloniferous. Leaves obovate, (2-)5-20(-30+) × (1-)2-5(-7) cm, margins pinna­ti-sect (lyrate to runcinate), remotely prickly, abaxial faces white-pannose, adaxial faces sparsely puberulent to arachnose, usually glandular as well. Heads 4-7 cm diam. (across the rays). Phyllaries: outer reflexed, apices mucronate, white-woolly; inner appressed, margins hyaline, apices rounded, glabrous. Ray florets 11-17(-25); corolla laminae abaxially greenish to purplish, adaxially yellow (drying to basally ochroleucous, apically blue, forming bull´s eye around disc), 10-25 × 2-4 mm, sparsely puberulent, glandular. Disc florets: corollas yellow proximally, bluish distally. Cypselae dark brown, 3 mm, densely woolly; pappi ca. 0.5 mm (usually hidden by hairs on cypselae).

Flowering Oct-Aug. Roadsides, old fields, other disturbed habitats; 0-300 m; introduced; Calif.; Africa.

Most populations of Arctotheca calendula are sterile and spread aggressively by stolons; at least three populations in the flora are fertile and highly invasive. The species is listed by the California Exotic Pest Plant Council (CalEPPC) as a weed with the potential to spread explosively (Red Alert, CDFA A).