Description from Flora of China
Shrubs, climbing, aromatic, pubescent or glabrous. Branches 4-angled, sometimes prickly. Leaves petiolate; leaf blade simple, crenate, often rugose. Inflorescences dense capitula, pedunculate; bracts exceeding calyx. Calyx small, membranous, truncate or sinuate dentate. Corolla nearly actinomorphic or slightly 2-lipped, tube slender; lobes 4 or 5, spreading. Stamens 4, didynamous, included. Ovary 2-locular. Style shorter than corolla tube; stigma obliquely subcapitate. Drupes with 2 1-seeded pyrenes.
About 150 species: tropical and subtropical America, one species naturalized in China.
Additional species grown as ornamentals.