Glen Shira is located at the northern end of a typical U-shaped valley, rising from sea level to above 500 m. It contains a large area of old sessile oak woodland. There are two distinct blocks of oak wood, separated by the River Shira and areas of open and grazed ground. Glen Shira is considered to be one of the richest woodland bryophyte (mosses and liverworts) sites in Scotland, with 128 species recorded within the western block alone.