An Indexed Bibliography. The Scientific Literature on Selected Herbs, and Aromatic and Medicinal Plants of the Temperate Zone. Horehound, Marrubium vulgare L., is a spreading perennial herb native to central and western Asia, southern Europe, and northern Africa and naturalized in parts of North America. Also known as common horehound, white horehound, and hoarhound, the plant reaches a height of almost 0.7 meters and is characterized by white, pubescent leaves, woolly stems, and continually blooming white flowers.
Commercial production is centered in France.
The hardy plant grows in full sun on poor, dry calcareous soils having good drainage. Although still collected from the wild, horehound is primarily grown in cultivated plantations for commercial uses. The crop is harvested and dried just prior to open bloom. The chief constituent of horehound is the bitter principle marrubium. The leaves and stems of horehound are often boiled and used in the preparation of candied products, cough drops, and syrups.