Annuals, 20-150+ cm. Leaf blades ± deltate to rhombic-deltate, 40-200+ × 25-150+ mm, lengths 1-2(-3+) times widths, margins ± toothed or entire. Peduncles 1-10+ cm. Outer phyllaries 5, connate 0-¹/6 their lengths, oblong to elliptic, (6-)12-15+ mm. Ray florets 8-13; corollas yellow-orange, laminae oblong-elliptic, 2.5-5+ × 1.6-3+ mm. Disc florets 30-45+. Fruits 4-7+ mm. 2n = 22, 24.

Flowering year round. Disturbed, usually moist sites; 10-50+ m; introduced; Calif.; Mexico; West Indies (Antilles); Central America.

Melampodium perfoliatum may be no longer present in California.