Lavender is a genus of 39 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, southern 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 colour named for the shade of the flowers of this species.
The genus includes annual or short-lived herbaceous perennial plants, and suffrutescent 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)
Commercially the plant is grown mainly for the production of essential oil of lavender. This has antiseptic and anti-inflammatory properties. These extracts are also used as fragrances for bath products. English lavender (Lavandula angustifolia) yields an essential oil with sweet overtones, and can be used in balms, salves, perfumes, cosmetics, and topical applications. Lavandin, Lavandula intermedia (also known as Dutch lavender), yields a similar essential oil, but with higher levels of terpenes including camphor, which add a sharper overtone to the fragrance. The lavandins Lavandula intermedia are a class of hybrids of L. angustifolia and L. latifolia. The lavandins are widely cultivated for commercial use, since their flowers tend to be bigger than those of English lavender and the plants tend to be easier to harvest, but lavandin oil is regarded by some to be of a lower quality than that of English lavender, with a perfume less sweet.
It is grown as a condiment and used in salads and dressings. Flowers yield abundant nectar from which bees make a high-quality honey. Monofloral honey is produced primarily around the Mediterranean, and is marketed worldwide as a premium product. Flowers can be candied and are sometimes used as cake decorations. Lavender flavours baked goods and desserts (it pairs especially well with chocolate), and is also used to make "lavender sugar". Lavender flowers are occasionally blended with black or green teas, or made into tisanes. Though it has many other traditional uses in southern France, lavender is not used in traditional southern French cooking. It does not appear at all in the best-known compendium of Provencal cooking, J.-B. Reboul's Cuisiniere Provencale In the 1970s, a herb blend called herbes de Provence usually including lavender was invented by spice wholesalers, and lavender has more recently become popular in cookery. Lavender lends a floral and slightly sweet flavour to most dishes, and is sometimes paired with sheep's-milk and goat's-milk cheeses. For most cooking applications the dried buds (also referred to as flowers) are used, though some chefs experiment with the leaves as well. Only the buds contain the essential oil of lavender, from which the scent and flavour of lavender are best derived. In the United States, both lavender syrup and dried lavender buds are used to make lavender scones and marshmallows.
The essential oil was used in hospitals during World War I. Lavender is used extensively with herbs and aromatherapy. Infusions are believed to soothe insect bites, burns, and headaches. Bunches of lavender repel insects. In pillows, lavender seeds and flowers aid sleep and relaxation.An infusion of flowerheads added to a cup of boiling water is used to soothe and relax at bedtime. Lavender oil (or extract of Lavender) is used to treat acne when diluted 1:10 with water, rosewater, or witch hazel; it also treats skin burns and inflammatory conditions. A recent clinical study investigated anxiolytic effects and influence on sleep quality. Lavender oil with a high percentage of linalool and linalyl acetate, in the form of capsules, was generally well tolerated. It showed meaningful efficacy in alleviating anxiety and related sleep disturbances. Lavender may be very effective with wounds; however, Lavender Honey (created from bees feeding on lavender plants), instead of lavender essential oil has the best effects of uninfected wounds.
Lavender oil can be a powerful allergen, and it is also recommended that it should not be ingested during pregnancy and breastfeeding. In vitro, lavender oil is cytotoxic. It increases photosensitivity as well. Lavender oil is cytotoxic to human skin cells in vitro (endothelial cells and fibroblasts) at a concentration of 0.25%. Linalool, a component of lavender oil, may be its active component. Aqueous extracts reduced mitotic index, but induced chromosomal aberrations and mitotic aberrations in comparison with control, significantly. Aqueous extracts induced breaks, stickiness, pole deviations and micronuclei. These effects were related to extract concentrations. However, according to a 2005 study "although it was recently reported that lavender oil, and its major constituent linalyl acetate, are toxic to human skin cells in vitro, contact dermatitis to lavender oil appears to occur at only a very low frequency.
The relevance of this in vitro toxicity to dermatological application of lavender oils remains unclear." In terms of phototoxicity, a 2007 investigative report from European researchers stated that, "Lavender oil and sandalwood oil did not induce photohaemolysis in our test system. However, a few reports on photosensitivity reactions due to these substances have been published, e.g. one patient with persistent light reaction and a positive photo-patch test to sandalwood oil." In 2007, a study was published in the New England Journal of Medicine which indicated that studies in human cell lines indicated that both lavender oil and tea tree oil had estrogenic and antiandrogenic activities. They concluded that repeated topical exposure to lavender and tea tree oils probably caused prepubertal gynaecomastia in some boys. The Aromatherapy Trade Council of the UK has issued a rebuttal, and it is also disputed by the Australian Tea Tree Association, a group that promotes the interests of Australian tea tree industry.
The ancient Greeks called the lavender herb nardus, after the Syrian city of Naarda (possibly the modern town of Dohuk, Iraq). It was also commonly called nard. The species originally grown was L. stoechas. Lavender was one of the holy herbs used in the biblical Temple to prepare the holy essence, and nard is mentioned in the Song of Solomon "nard and saffron, calamus and cinnamon, with every kind of incense tree, with myrrh and aloes, and all the finest spices. During Roman times, flowers were sold for 100 denarii per pound, which was about the same as a month's wages for a farm laborer, or fifty haircuts from the local barber. Its late Latin name was lavandarius, from lavanda (things to be washed), from the verb lavare (to wash). The Greeks discovered early on that lavender if crushed and treated correctly would release a relaxing fume when burned. In medieval times powdered lavender was used as a condiment.