Lavandula

The genus includes annual or short-lived herbaceous perennial plants, and shrub-like perennials, subshrubs or small shrubs.[4]

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.[4]

Flowers are contained in whorls, held on spikes rising above the foliage, 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 calyx is tubular. The corolla is also tubular, usually with five lobes (the upper lip often cleft, and the lower lip has two clefts).[4][5]

Lavandula stoechas, L. pedunculata, and L. dentata were known in Roman times.[6] 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 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.[6]

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).[7]

Lavandula has three subgenera:[8]

• 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.[4]

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.

Thus 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.

The English word lavender is generally thought to be derived from Old French lavandre, ultimately from the Latin lavare (to wash), referring to the use of infusions of the plants.[9] The botanic name Lavandula as 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 be derived from Latin livere, "blueish".[10]

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".[11] The name "French lavender" may refer to either L. stoechas or to L. dentata. "Spanish lavender" may refer to L. stoechas, L. lanata, or L. dentata.

A honey bee on a lavender flower

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, L. dentata, 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. Such spontaneous growth is usually harmless, 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.[12] It is regarded as a weed in parts of Spain.[13]

Lavenders flourish best in dry, well-drained, sandy or gravelly soils in full sun.[14] English lavender has a long germination process (14–28 days) and matures within 100–110 days.[15] 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.[16] It grows best in soils with a pH between 6 and 8.[17] Most lavender is hand-harvested, and harvest times vary depending on intended use.[17]

Commercially, the plant is grown mainly for the production of lavender essential oil. English lavender (Lavandula angustifolia) yields an oil with sweet overtones and can be used in balms, salves, perfumes, cosmetics, and topical applications.[18] Lavandula × intermedia, also known as lavandin or Dutch lavender, hybrids of L. angustifolia and L. latifolia.[19] 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.[20] They yield a similar essential oil, but with higher levels of terpenes including camphor, which add a sharper overtone to the fragrance, regarded by some as of lower quality than that of English lavender.

The US Food and Drug Administration considers lavender as generally recognized as safe (GRAS) for human consumption.[21] The essential oil was used in hospitals during World War I.[14]

Lavender-flavored cupcakes

Culinary lavender is usually English lavender, the most commonly used species in cooking (L. angustifolia 'Munstead'). As an aromatic, it has a sweet fragrance with lemon or citrus notes.[23] It is used as a spice or condiment in pastas, salads and dressings, and desserts.[24][25] Their buds and greens are used in teas, and their buds, processed by bees, are the essential ingredient of monofloral honey.[26]

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 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.[32] Dried lavender flowers may be used for wedding confetti. Lavender is also used in scented waters and sachets.

The ancient Greeks called the lavender herb νάρδος: nárdos, Latinized as nardus, after the Syrian city of Naarda (possibly the modern town of Duhok, Iraq). It was also commonly called nard.[33] The species originally grown was L. stoechas.[4]

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).[34]

Culinary history

Spanish nard (Old French: "spykenard de spayn le pays"), referring to L. stoechas, is listed as an ingredient in making a spiced wine, namely hippocras, in The Forme of Cury.[35]

Lavender was introduced into England in the 1600s. It is said that Queen Elizabeth prized a lavender conserve (jam) at her table, so lavender was produced as a jam at that time, as well as used in teas both medicinally and for its taste.[23]

Lavender was not used in traditional southern French cooking at the turn of the 20th century. It does not appear at all in the best-known compendium of Provençal cooking, J.-B. Reboul's Cuisinière Provençale.[36] French lambs have been allowed to graze on lavender as it is alleged to make their meat more tender and fragrant.[23] In the 1970s, a blend of herbs called herbes de Provence was invented by spice wholesalers. Culinary lavender is added to the mixture in the North American version.[37]

In the 21st century, lavender is used in many world regions to flavor tea, vinegar, jellies, baked goods, and beverages.[38]

Bunches of lavender for sale, intended to repel insects

The German scientific committee on traditional medicine, Commission E, reported uses of lavender flower in practices of herbalism, including its use for restlessness or insomnia, Roemheld syndrome, intestinal discomfort, and cardiovascular diseases, among others.[39]

The U.S. National Center for Complementary and Integrative Health (NCCIH) states that lavender is considered likely safe in food amounts, and that topical uses may cause allergic reactions.[40] NCCIH does not recommend the use of lavender while pregnant or breastfeeding because of lack of knowledge of its effects.[40] It recommends caution if young boys use lavender oil because of possible hormonal effects leading to gynecomastia.[40][41][42]

A 2007 study examined the relationship between various fragrances and photosensitivity, stating that lavender is known "to elicit cutaneous photo-toxic reactions", but does not induce photohaemolysis.[43]

Different lavender cultivars grown at Snowshill, Cotswolds.

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

Lavender field in Carshalton, London Borough of Sutton.

Field in Hitchin, England, UK

• 
  Lavender flower
• 
  Flower of cultivated lavender; Lavandula stoechas
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  Lavender garden, India
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  Lavandula fields near Drama
• 
  The flower of Lavandula angustifolia.
• 
  Lavender growing at Kula Lavender Farm located in Maui, Hawaii

• Upson T, Andrews S. The Genus Lavandula. Royal Botanic Gardens, Kew 2004
• United States Department of Agriculture GRIN: Lavandula

Wikimedia Commons has media related to Lavandula.

• Lavandula at Curlie