A low, partially evergreen, aromatic bush, quite woody at the base, 11⁄2 to 2 ft high; shoots erect, green, square, covered when young with minute down. Leaves opposite, linear or narrowly oval, 1⁄3 to 11⁄2 in. long, 1⁄16 to 1⁄4 in. wide, tapered at both ends, very minutely toothed, or roughened at the edges, rich green, glandular-punctate on both surfaces. Flowers produced in close, axillary whorls on the shoots of the year, forming a terminal panicle, and starting to open about midsummer and continuing until September. From six to twelve or more flowers appear in each whorl, and they of a bluish purple shade in the type, about 1⁄2 in. long, two-lipped. Stamens exserted. As in all the labiates the fruit consists of four nutlets. The leaves and young shoots have a pleasant mint-like scent. Bot. Mag., t. 2299.
Native of S. Europe, in the Mediterranean region, and W. Asia. Cultivated as a medicinal herb in England since 1548, probably long before. An infusion of hyssop is an old-fashioned remedy for removing phlegm. It is an easily cultivated plant requiring a warm, light soil, and is easily increased by cuttings during the summer and autumn. There is a white-flowered form, f. albus (West.) Schneid., and one with red flowers, f. ruber (West.) Hegi, both known in the wild and both in cultivation since at least the 18th century.
H. officinalis is a variable species. A race found in the central and eastern Pyrenees was named H. aristatus by Godron but has been treated as a subspecies by later authorities. The distinguishing characters given are: leaves of a cheerful green, glabrous, scarcely glandular-punctate beneath; flowers in dense spikes; bracts and calyx-teeth terminated by fine, long, aristate tips. Cultivated plants are of dense rather fastigiate habit, 11⁄4 to 11⁄2 ft high.