Oaks, elms, firs, ashes and beeches are the principal forest trees.
On the mountains the trees are chiefly pines, firs, spruce and hemlock.
High districts covered with oaks and chestnuts succeed to this almost tropical vegetation; a little higher up and we reach the elevated regions of the Pollino and the Sila, covered with firs and pines, and affording rich pastures even in the midst of summer, when heavy dews and light frosts succeed each other in July and August, and snow begins to appear at the end of September or early in October.
Witches-brooms are the tufted bunches of twigs found on silver firs, birches and other trees, and often present resemblances to birds nests or clumps of mistletoe if only seen from a distance.
It is the common result of fires passing alongtoo rapidly to burn the trees; and thin-barked treeshornbeam, beech, firs, &c. may exhibit it as the results of sunburn, especially when exposed to the south-west after the removal of shelter.