Erect perennial herb 30-90 cm high reproducing by seeds or from rhizomes at the base of the stem. Stems much branched, 2-sided or ridged with black glands along the ridges, hairless, a distinctly dark ring at the lower nodes. Leaves simple, opposite, pinnately netted, with no stalk, usually without teeth, hairless with translucent dots, apex rounded. Flowers showy, yellow, in fairly flat-topped clusters at the top of the plant. Sepals 5, green, lance-shaped,...