With thanks to WIKIPEDIA
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. 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 actually be derived from Latin livere, “blueish.”
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 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.
Leaf shape is diverse across the genus. They are simple in some commonly cultivated species; in others they are pinnately toothed, orpinnate, 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.)