The genus includes annual or short-lived herbaceous perennial plants, and shrub-like perennials, subshrubs or small shrubs.
Leaf shape is diverse across the genus. They are simple in some commonly cultivated species; in other species they are pinnately toothed, or pinnate, sometimes multiple pinnate and dissected. In most species the leaves are covered in fine hairs or indumentum, which normally contain the essential oils.
Flowers are borne in whorls, held on spikes rising above the foliage, the spikes being branched in some species. Some species produce coloured bracts at the apices. The flowers may be blue, violet or lilac in the wild species, occasionally blackish purple or yellowish. The calyx is tubular. The corolla is also tubular, usually with five lobes (the upper lip often cleft, and the lower lip has two clefts).More recently, work has been done by Upson and Andrews, and currently Lavandula is considered to have three subgenera.
Subgenus Lavandula is mainly of woody shrubs with entire leaves. It contains the principal species grown as ornamental plants and for oils. They are found across the Mediterranean region to northeast Africa and western Arabia.
Subgenus Fabricia consists of shrubs and herbs, and it has a wide distribution from the Atlantic to India. It contains some ornamental plants.
Subgenus Sabaudia constitutes two species in the southwest Arabian peninsula and Eritrea, which are rather distinct from the other species, and are sometimes placed in their own genus Sabaudia.
In addition, there are numerous hybrids and cultivars in commercial and horticultural usage.