Trees in the subalpine zone often become crooked, stunted and twisted in form. At treeline, tree seedlings may germinate on the lee (sheltered) side of rocks and grow only as high as the rock shelters them from wind. Further growth is more horizontal than vertical, and additional rooting may occur where branches touch the soil. Snow cover may protect trees during the winter, but branches higher than wind-shelters or snow cover are usually destroyed. Well-established trees may be several hundred to a thousand years old.