Lavandula (common name lavender) is a genus of 39 known species of flowering plants in the mint family, Lamiaceae. It is native to the Old World and is found from Cape Verde and the Canary Islands, Europe across to northern and eastern Africa, the Mediterranean, southwest Asia to southeast India. Many members of the genus are cultivated extensively in temperate climates as ornamental plants for garden and landscape use, for use as culinary herbs, and also commercially for the extraction of essential oils. The most widely cultivated species, Lavandula angustifolia, is often referred to as lavender, and there is a color named for the shade of the flowers of this species.
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 others 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).
nomenclature and taxonomy
Lavandula stoechas, Lavandula pedunculata and Lavandula dentata were known in Roman times. From the Middle Ages onwards, the European species were considered two separate groups or genera, Stoechas (Lavandula stoechas, Lavandula pedunculata, Lavandula dentata) and Lavandula (Lavandula spica and Lavandula latifolia), until Linnaeus combined them. He only recognised five species in Species Plantarum (1753), Lavandula multifida and Lavandula dentata (Spain) and Lavandula stoechas and Lavandula spica from Southern Europe. Lavandula pedunculata was included within L. stoechas.
By 1790, Lavandula pinnata and Lavandula carnosa were recognised. The latter was subsequently transferred to Anisochilus. By 1826 Frédéric Charles Jean Gingins de la Sarraz listed 12 species in three sections, and by 1848 eighteen species were known.
One of the first modern major classifications was that of Dorothy Chaytor in 1937 at Kew. The six sections she proposed for 28 species still left many intermediates that could not easily be assigned. Her sections included Stoechas, Spica, Subnudae, Pterostoechas, Chaetostachys and Dentatae. However all the major cultivated and commercial forms resided in the Stoechas and Spica sections. There were four species within Stoechas (Lavandula stoechas, Lavandula dentata, Lavandula viridis and Lavandula pedunculata) while Spica had three (Lavandula officinalis (now Lavandula angustifolia), Lavandula latifolia and Lavandula lanata). She believed that the garden varieties were hybrids between true lavender Lavandula angustifolia and spike lavender (Lavandula latifolia).
More recently, work has been done by Upson and Andrews, and currently Lavandula is considered to have three subgenera:
1) 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.
2) Subgenus Fabricia consists of shrubs and herbs, and it has a wide distribution from the Atlantic to India. It contains some ornamental plants.
3) 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.