Leaves (needles) are flattened, dark-green with a medial groove on the upper side and two broad silvery-white bands on the lower surface. These bands consist of several rows of stomata (pores). Leaves are 1/2 to one inch long, have a broad circular base, and are usually dark green on the upper surface and lighter on the lower surface. On lower branches, leaves are two-ranked (occurring in two opposite rows). On upper twigs, leaves tend to curl upward forming a more "U-shaped" appearance. Bark is usually gray or gray-brown, thin, smooth with numerous resin blisters on young trees. As trees become older, the bark tends to develop into thin, papery scales. The combination of form, needle retention, dark blue-green color, pleasant scent and excellent shipping characteristics has led to Fraser fir being a most popular Christmas tree species. It requires from 7 to 10 years in the field to produce a 6-7 feet tree.