Annual, biennial or perennial herbs, sometimes suffruticose and/or monocarpic, usually pubescent, floccose or tomentose. Leaves alternate (very rarely opposite), simple or divided, basal ones in a rosette. Plants glabrous or with indumentum of eglandular or glandular, simple, branched or dendroid hairs. Inflorescence a branched or unbranched spike or raceme or a panicle of racemes or spikes, flowers solitary or fasciculate in bract axils. Calyx 5-lobed, regular or ± zygomorphic. Corolla yellow (in our species) or rarely purple-violet, reddish, brownish or bluish-green, ± actinomorphic or slightly zygomorphic, flattened-rotate, tube very short or almost absent; lobes rounded or broadly obovate, posterior ones slightly smaller. Stamens 4 (didynamous) or 5, or 4 ferile and 1 staminode. Filaments inserted at base of corolla, either all equal in length and villous up to anthers, or 2 posterior longer and ± glabrous above. Anthers either all reniform and medifixed, or 2 anterior oblong or oblong-linear and adnate-decurrent or obliquely inserted on to filament. Style filiform or thickened towards apex. Ovary bilocular. Capsule globose, oblong-ovoid, spathulate or cylindrical, septicidal. Seeds numerous, obconical-prismatic, foveolate. 

A large genus of c. 360 species; throughout Eurasia (E. to China), N. and eastern Tropical Africa and Arabia but with a very high proportion of species in Turkey, Iran and Afghanistan, and very few species further east. Only 5 species in Pakistan, one of which may have been introduced from western Europe.

Verbascum and Celsia were classified in distinct classes by Linnaeus but this separation is now regarded as artificial. The two genera, based largely on the number of stamens (4 or 5), are linked by intermediate species in which the fifth stamen is incomplete and sterile. Following modern accepted tradition, the two groups are treated here as a single genus.