The area above about 800 meters belongs to the Japanese beech tree zone, and near the top of Mt. Obako-dake, there grow deciduous broadleaf trees including Japanese beech tree, mizunara (quercus mongoloca var. grosseseratta), Japanese hornbeam, yashabushi (alnus firma) and okamenoki (viburnum furcatum), and the trees on the top are stunted by wind and snow.
800メートルあたりからはブナ林帯に入り、伯母子岳山頂周辺では、ブナ、ミズナラ、クマシデ、ヤシャブシ、オオカメノキなどの落葉広葉樹があり、山頂部の樹木には風雪の影響による矮化が見られる。