lavender

Lavender
Lavender flowers with bracts
Scientific classification
Kingdom:	Plantae
Phylum:	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Lamiales
Family:	Lamiaceae
Subfamily:	Nepetoideae
Tribe:	Lavanduleae
Genus:	Lavandula L.
Type species
Lavandula spica L.
Species
39 species, including some hybrids, see text.

The lavenders (botanic name Lavandula) 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 Canary Islands, southern Europe across to northern and eastern Africa, the Mediterranean, south-west Asia to south-east India. Many members of the genus are cultivated extensively in temperate climates as ornamental plants for garden and landscape use, and also commercially for the extraction of essential oils.

Botany

Description

The genus includes herbaceous annual or short lived herbaceous perennial plants (the species from India), and suffruticose perennials, subshrubs or small shrubs across most of the rest of its distribution. ^[1]

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.^[1]

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, with five lobes, the upper lip often cleft, and the lower lip 3-cleft. ^{[2] [1]}

Nomenclature and taxonomy

L. stoechas, L. pedunculata and L. dentata were described in Roman times (Lis-Balchin 2002). From the Middle Ages onwards, the European species were considered two separate groups or genera, Stoechas (LL. stoechas, pedunculata, dentata) and Lavandula (LL. spica, latifolia), until Linnaeus combined them. He only recognised 5 species in the 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 de Lassaras described 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). ^[3]

More recently work has been done by Upson and Andrews, and currently Lavandula is considered to have 3 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. ^[1]

Distribution

The native range extends across the Canary Islands and Madeira, North and East Africa, Southern Europe and the Mediterranean, Arabia and India. Some of its members are found as naturalised plants and weeds elsewhere.

It is thought the genus originated in Asia but it is most diversified in its western distribution.^{[citation needed]}

Names

The English word lavender is generally thought to be derived from Old French lavandre, to wash, ultimately from the Latin lavare (to wash), referring to the use of infusions of the plants. ^[4] The botanic name Lavandula was used by Linnaeus is considered to be derived from this and other European vernacular names for the plants. However it is suggested that this explanation may be apocryphal, and that the name may actually be derived from Latin livere, "blueish". ^[5]

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".^[6] The name "French lavender" may be used to refer to either L. stoechas or to L. dentata. "Spanish lavender" may be used to refer to L. stoechas, L. lanata or L. dentata.

Usage

The accounts provided here apply mostly to those plants grown for ornament and for oil extraction, which are all from the Mediterranean region.

Ornamental garden

The most common form in cultivation is the common or English lavender Lavandula angustifolia (formerly named L. officinalis). A wide range of cultivars can be found. Other commonly grown ornamental species are L. stoechas, (Spanish lavender) L. dentata (French lavender), and L. multifida (Egyptian lavender).

Because the cultivated forms are planted in gardens worldwide, they are occasionally found growing wild as garden escapes, well beyond their natural range. Commonly such adventitious establishment is apparently harmless at worst, but in some cases Lavandula species have become invasive; for example, in Australia Lavandula stoechas has become a cause for concern; it occurs widely throughout the continent, and has been declared a noxious weed in Victoria since 1920.^[7] It also is regarded as a weed in parts of Spain.^[8]

Oil production

Commercially the plant is grown mainly for the production of essential oil of lavender. This has antiseptic and anti-inflammatory properties.^[9][10] 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.^[11] 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.^[12]

Culinary use

A bee on a lavender flower

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 flavors baked goods and desserts (it pairs especially well with chocolate), and is also used to make "lavender sugar".^[13] Lavender flowers are occasionally blended with black, green, or herbal tea, adding a fresh, relaxing scent and flavor.

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 Provençal cooking, J.-B. Reboul's Cuisinière Provençale ^[14] In the 1970s, a herb blend called herbes de Provence usually including lavender was invented by spice wholesalers,^[15] and lavender has more recently become popular in cookery.

Lavender lends a floral and slightly sweet flavor 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 flavor of lavender are best derived.

In the United States, both lavender syrup and dried lavender buds are used to make lavender scones and marshmallows.

Medical uses

The essential oil was used in hospitals during World War I to disinfect floors and walls.

Lavender is used extensively with herbs and aromatherapy. According to folk wisdom, lavender has many uses. Infusions of lavender are believed to soothe insect bites, burns, and headaches. Bunches of lavender repel insects.^{[citation needed]} In pillows, lavender seeds and flowers aid sleep and relaxation.^{[citation needed]} An infusion of flowerheads added to a cup of boiling water soothes and relaxes at bedtime. Lavender oil (or extract of Lavender) heals acne when used diluted 1:10 with water, rosewater, or witch hazel; it also treats skin burns and inflammatory conditions.^{[citation needed]}

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.^[16]

Health precautions

Lavender oil can be a powerful allergen, and it is also recommended that it should not be ingested during pregnancy and breastfeeding.^[17]

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.^[18] 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.^[19]

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."^[20]

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."^[21]

Controversy over possible endocrine-disrupting activity

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.^[22] The Aromatherapy Trade Council of the UK has issued a rebuttal, ^[23] and it is also disputed by the Australian Tea Tree Association, a group that promotes the interests of Australian tea tree industry.^[24]

Other uses

Lavender products for sale at the San Francisco Farmers Market.

Flower spikes are used for dried flower arrangements. The fragrant, pale purple flowers and flower buds are used in potpourris. Lavender is also used extensively as herbal filler inside sachets used to freshen linens. Dried and sealed in pouches, lavender flowers are placed among stored items of clothing to give a fresh fragrance and to deter moths. Dried lavender flowers have become recently popular for wedding confetti. Lavender is also popular in scented waters and sachets.

Cultivation

Lavenders flourish best in dry, well-drained, sandy or gravelly soils in full sun.^[25] All types need little or no fertilizer and good air circulation. In areas of high humidity, root rot due to fungus infection can be a problem. Organic mulches can trap moisture around the plants' bases, encouraging root rot. Gravelly materials such as crushed rocks give better results. ^[26]

In history and culture

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.^[27] The species originally grown was L. stoechas. ^[28]

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 (4,14)

nard and saffron,^[29]
calamus and cinnamon,
with every kind of incense tree,
with myrrh and aloes,
and all the finest spices.^[30]

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 lavandārius, from lavanda (things to be washed), from the verb lavāre (to wash).^[31] The Greeks discovered early on that lavender if crushed and treated correctly would release a relaxing fume when burned.^{[citation needed]}

In medieval times powdered lavender was used as a condiment. ^[32]

Taxonomic table

This is based on the classification of Upson and Andrews, 2004.

See also

• Lavender oil
• Lavender (color)

Gallery

• 

  Lavender flower

• 

  Flower of cultivated lavender; Lavandula stoechas

• 

  Hardy and disease resistant; Lavandula Intermedia or Silver Edge lavender.

• 

  A field of lavender in France

• 

  A field of lavender in England

• 

  Female of unidentified species feeding. Note the long labrum

References

Sources

• Chaytor D A. A taxonomic study of the genus Lavandula. 1937
• Lis-Balchin M (ed.). Lavender: The genus Lavandula. Taylor and Francis 2002
• Upson T, Andrews S. The Genus Lavandula. Royal Botanic Gardens, Kew 2004
• United States Department of Agriculture GRIN: Lavandula
• Joan Head: The Lavenders
• Everything Lavender

External links

Wikisource has the text of the 1911 Encyclopædia Britannica article Lavender.

Wikispecies has information related to: Lavandula

Media related to Lavandula at Wikimedia Commons

• Medicinal use from University of Maryland Medical Center