henbane, (Hyoscyamus niger), highly toxic plant of the nightshade family (Solanaceae), native to Eurasia and naturalized throughout much of the world. The dried leaves of henbane, and sometimes those of Egyptian henbane (H. muticus) and white henbane (H. albus), yield three medicinal alkaloids—atropine, hyoscyamine, and scopolamine—that can be purified for use in pharmaceuticals. The plants also are sometimes used in herbal and folk medicine. The leaves are used in illicit preparations of smoking mixtures and, in India, as a beverage. The plant can be fatal if eaten.
Henbane plants have a branching taproot and feature large alternately arranged leaves with irregular lobes. The stems and leaves are covered in glandular hairs (trichomes), and the whole plant has a powerful nauseous odour. The showy funnel-shaped flowers have five cream to dark yellow petals with purple veins and dark centres. The fruit is a capsule with numerous black seeds. There are two forms of the plant, an annual and a biennial. The annual grows during the summer to a height of 30 to 60 cm (1 to 2 feet) and then flowers and sets seed. The biennial produces during the first season only a tuft of basal leaves, which disappear in winter and leave underground a thick fleshy root. The following spring, the plant produces a branched flowering stem, which is usually much taller and more vigorous than the flowering stems of the annual plants.