Lavandula (common name lavender) is a genus of 47 known species of perennial flowering plants in the sage family, Lamiaceae. It is native to regions of the Iberian Peninsula and Mediterranean coastline (including the Adriatic coast and coastal North Africa), the Middle East, extending to the Indian subcontinent. 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 commercially for the extraction of essential oils. Lavender is used in traditional medicine and as an ingredient in cosmetics.
Description
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 essential oils. Flowers are contained in whorls, held on spikes rising above the foliage, with the spikes being branched in some species. Some species produce colored bracts at the tips of the inflorescences. The flowers may be blue, violet, or lilac in the wild species, occasionally blackish purple or yellowish. The sepal calyx is tubular. The corolla is also tubular, usually with five lobes (the upper lip often cleft, and the lower lip has two clefts).
Phytochemicals Around 93 individual phytochemicals have been identified in lavender oil, including major contents of linalyl acetate (30–55%), linalool (20–35%), tannins (5–10%), and caryophyllene (8%), with lesser amounts of sesquiterpenoids, perillyl alcohols, esters, oxides, ketones, cineole, camphor, beta-ocimene, limonene, caproic acid, and caryophyllene oxide. The relative amounts of these compounds vary considerably among lavender species.
Taxonomy
Lavandula stoechas, L. pedunculata, and L. dentata were known in Roman times. From the Middle Ages onwards, the European species were considered two separate groups or genera, Stoechas (L. stoechas, L. pedunculata, L. dentata) and Lavandula (L. spica and L. latifolia), until Carl Linnaeus combined them. He recognised only five species in Species Plantarum (1753), L. multifida and L. dentata (Spain) and L. stoechas and L. spica from Southern Europe. L. pedunculata was included within L. stoechas. By 1790, L. pinnata and L. 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, L. dentata, L. viridis, and L. pedunculata) while Spica had three (L. officinalis—now L. angustifolia—L. latifolia and L. lanata). She believed that the garden varieties were hybrids between true lavender L. angustifolia and spike lavender (L. latifolia). Lavandula has 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. The first major clade corresponds to subgenus Lavandula, and the second Fabricia. The Sabaudia group is less clearly defined. Within the Lavandula clade, the subclades correspond to the existing sections but place Dentatae separately from Stoechas, not within it. Within the Fabricia clade, the subclades correspond to Pterostoechas, Subnudae, and Chaetostachys. The current classification includes 39 species distributed across 8 sections (the original 6 of Chaytor and the two new sections of Upson and Andrews), in three subgenera (see table below). However, since lavender cross-pollinates easily, countless variations present difficulties in classification.
Taxonomic table This is based on the classification of Upson and Andrews, 2004.
Etymology The English word lavender came into use in the 13th century, and is generally thought to derive from Old French lavandre, ultimately from Latin lavare from lavo (to wash), referring to the use of blue infusions of the plants for bathing. The botanic name Lavandula as used by Linnaeus is considered to be derived from this and other European vernacular names for the plants. The names widely used for some of the species, "English lavender", "French lavender" and "Spanish lavender" are all imprecisely applied. "English lavender" is commonly used for L. angustifolia, though some references say the proper term is "Old English lavender". The name "French lavender" may refer to either L. stoechas or to L. dentata. "Spanish lavender" may refer to L. pedunculata, L. stoechas, or L. lanata.
Cultivation
… excerpt ends here. Continue reading the full article.
