A great variety of shrubs grow on these slopes of the western Caucasus, chiefly the following species, several of which are indigenous - Rhododendron ponticum, Azalea pontica, Aristotelia maqui, Agave between 1864 and 1878, and the country where they had lived remained for the most part unoccupied until after the beginning of the 10th century.
Growing under the shade of these are several varieties of rose, honeysuckle, currant, gooseberry, hawthorn, rhododendron and a luxuriant herbage, among which the ranunculus family is important for frequency and number of genera.
The peach, horse-chestnut, lilac, morello cherry, black currant, rhododendron and many other trees and shrubs develop flower-buds for the next season speedily after blossoming, and these may be stimulated into premature growth.
Professor Macoun gives us a few notable species - Calluna vulgaris, Salisb., Alchemilla vulgaris, L., Rhododendron maximum, L., Ilex glabia, Gray, Hudsonia ericoides, L., Gaylussacia dumosa, F.
Sogdiana), and a copious undergrowth of shrubs familiar in European gardens, such as Rhododendron chrysanthum, Sorbus aucuparia (rowan), Berberis heteropoda (berberry), Lonicera Tatarica (honeysuckle) and Crataegus (hawthorn).
The forest extends, with great luxuriance, to an elevation of 12,000 ft., above which the sub-alpine region may be said to begin, in which rhododendron scrub often covers the ground up to 13,000 or 14,000 ft.
Three species of rhododendron vie with each other in the brilliancy of their masses of red or pink flowers; the common juniper rises higher still, along with three species of bilberry; and several dwarf willows attain nearly to the utmost limit of vegetation.
During the milder interglacial period some southern types, such as Rhododendron ponticum, still held their own, but ultimately succumbed.
Many flowering and fruit-bearing shrubs of the heath family add to the beauty of the mountainous districts, rhododendron and kalmia often forming impenetrable thickets.
In the eastern forests the prevalence of Magnoliaceae and of Clethra and Rhododendron continues the alliance with eastern Asia.