The flowers emit when rubbed a delightful fragrance, and have a pleasant aromatic taste. The leaves of the plant are oblong linear, or lanceolate, revolute at the margin and very hoary when young.
For pharmaceutical use or as a perfume, lavender flowers are stripped from the stalks and dried by a gentle heat. They are but seldom kept in the shops, being grown almost entirely for the sake of their essential oil.
Production of Essential Oil—Lavender is cultivated in the parishes of Mitcham, Carshalton and Beddington and a few adjoining localities, all in Surrey, to the extent of about 300 acres. It is also grown at Market Deeping in Lincolnshire; also at Hitchin in Hertfordshire, where lavender was apparently cultivated as early as the year 1568.[1746]
At the latter place there were in 1871 about 50 acres so cropped.
The plants which are of a small size, and grown in rows in dry open fields, flower in July and August. The flowers are usually cut with the stalks of full length, tied up in mats, and carried to the distillery there to await distillation. This is performed in the same large stills that are used for peppermint. The flowers are commonly distilled with the stalks as gathered, and either fresh, or in a more or less dry state. A few cultivators distill only the flowering heads, thereby obtaining a superior product. Still more rarely, the flowers are stripped from the stalks, and the latter rejected in toto.[1747] According to the careful experiments of Bell,[1748] the oil made in this last method is of exceedingly fine quality. The produce he obtained in 1846 was 26½ ounces per 100 lb. of flowers, entirely freed from stalks; in 1847, 25½ ounces; and in 1848, 20 ounces: the quantities of flowers used in the respective years were 417, 633, and 923 lb. Oil distilled from the stalks alone was found to have a peculiar rank odour. In the distillation of lavender, it is said that the oil which comes over in the earlier part of the operation is of superior flavour.
We have no accurate data as to the produce of oil obtained in the ordinary way, but it is universally stated to vary extremely with the season. Warren[1749] gives it as 10 to 12 lb., and in an exceptional case as much as 24 lb. from the acre of ground under cultivation. At Hitchin,[1750] the yield would appear to approximate to the last named quantity. The experiments performed in Bell’s laboratory as detailed above, show that the flowers deprived of stalks afforded on an average exactly 1½ per cent. of essential oil.
Oil of Lavandula vera is distilled in Piedmont, and in the mountainous parts of the South of France, as in the villages about Mont Ventoux near Avignon, and in those some leagues west of Montpellier (St. Guilhen-le-désert, Montarnaud and St. Jean de Fos)—in all cases from the wild plant. This foreign oil is offered in commerce of several qualities, the highest of which commands scarcely one-sixth the price of the oil produced at Mitcham.[1751] The cheaper sorts at least are obtained by distilling the entire plant.
Chemical Composition—The only constituent of lavender flowers that has attracted the attention of chemists is the essential oil (Oleum Lavandulæ). It is a pale yellow, mobile liquid, varying in sp. gr. from 0·87 to 0·94 (Zeller), having a very agreeable odour of the flowers and a strong aromatic taste. The oil distilled at Mitcham (1871) we find to rotate the plane of polarization 4·2° to the left, in a column of 50 mm.
Oil of lavender seems to be a mixture in variable proportions of oxygenated oils and stearoptene, the latter being identical, according to Dumas, with common camphor. In some samples it is said to exist to the extent of one-half, and to be sometimes deposited from the oil in cold weather; we have not however been able to ascertain this fact. The oil according to Lallemand (1859) appears also to contain compound ethers.
Commerce—Dried lavender flowers are the object of some trade in the south of Europe. According to the official Tableau général du Commerce de la France, Lavender and Orange Flowers (which are not separated) were exported in 1870 to the extent of 110,958 kilo. (244,741 lb.),—chiefly to the Barbary States, Turkey and America. There are no data to show the amount of oil of lavender imported into England.