The aliases of the balsam fir include blister fir, white fir, balm of Gilead, church steeple and silver pine. The resin from balsam firs is used in Canada balsam, a paste that is used for attaching specimens to microscope slides. The resin and the bark can be used for food, but they should only be used in emergencies, because they often have an unpleasant taste. The balsam fir usually reaches heights of 40 to 62 feet. Its long, flat, shiny needles are dark green with whitish undersides, and do not grow all around the branch but only on the sides. Its light bark has resin bubbles in it, which helps to distinguish the balsam fir from other evergreens. The balsam fir is often used for Christmas trees because it keeps its needles even after being cut.