This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Dwarf compact branching shrubs. Leaves opposite, entire or toothed. Flowers small, on long-stalked spikes. Calyx ovate, ribbed, unequally toothed. Corolla with a 2-lobed upper, and 3-lobed lower lip. Stamens and style concealed in the corolla. A small genus of plants from the Mediterranean region. The name is derived from lavare, to wash, in allusion to the use of the plant by the ancients to perfume their baths.
1. L. vera. Common Lavender. - A variable undershrub with narrow lanceolate entire hoary or nearly glabrous leaves and terminal verticillate spikes of small blue flowers on a very long peduncle. L. Spica closely resembles L. vera, and is perhaps a form of the same species. It differs, according to Decandolle, in its dwarfer habit, whiter tomentum, leaves crowded towards the base of the branches, and shorter denser flower-spikes.
L. lanata belongs to the same group, but the leaves are broader, and clothed on both sides with a thick velvety white tomentum. L. Staochas and L. dentata are handsome species belonging to a group distinguished by the dense spikes being surmounted with a crown of coloured foliaceous bracts. The former has narrow entire, and the latter finely-toothed leaves.
The genus Mentha, distinguished by the axillary or spiked verticillasters of small nearly regular flowers with four almost equal spreading stamens, offers little that is ornamental, though the fragrance of some of the species might entitle them to a place in the flower-garden. M. piperita, Peppermint, is a sub-erect plant with glabrous oblong-lanceolate serrate petiolate leaves, and spicate inflorescence. M. Pulegium, Pennyroyal, is prostrate, creeping, with small ovate-oblong serrate leaves and clusters of flowers in the axils of the lower leaves. M. rotundifolia is an erect plant with roundish crenate wrinkled sessile woolly leaves and dense terminal spikes of white or pink flowers, of which there is a good variety with variegated foliage.