Hyssop is a brightly coloured shrub or subshrub that ranges from 30 to 60 cm (12 to 24 in) in height. The stem is woody at the base, from which grow a number of straight branches. Its leaves are lanceolate, dark green in colour, and from 2 to 2.5 cm (0.79 to 0.98 in) long.
During the summer, the plant produces bunches of pink, blue, or, more rarely, white fragrant flowers. These give rise to small oblong acheenes.