Glabrous annual or perennials. Basal leaves rosulate, the upper ones alternate, entire, Inflorescence a raceme or a corymb. Flowers usually small, bracteolate. Calyx campanulate, 5-lobed. Corolla rotate, exceeding the calyx. Stamens 5, epipetalous, opposite the corolla lobes and alternating with staminodes; staminodes linear or broad, present between the sinuses of the lobes. Ovary semi-inferior, style short, stigma subcapitate. Capsule dehiscence valvular. Seeds many, small.
Because of the presence of a semi-inferior ovary, Samolus is given a somewhat isolated position within the Primulaceae; this view is supported to some extent by the seed morphology and the corollar epidermal structure. The genus has been variously assigned to the level of a tribe (Samoleae, by authors as Duby (1844), Boissier (1879), Knuth (1905 etc.) or a family (Samolaceae, Dumortier, Anal. Fam. Pl. 29. 1829).