reindeer lichen, (Cladonia rangiferina), a fruticose (bushy, branched) lichen found in great abundance in Arctic lands. The lichen covers immense areas in northern tundra and taiga ecosystems and serves as pasture for reindeer, moose, caribou, and musk oxen. In Scandinavia it has been used in the manufacture of alcohol, but difficulties in obtaining reindeer lichen arise because of its slow growth rate (3 to 5 mm [0.12 to 0.2 inch] per year). The name is also applied to the related lichen Cladonia portentosa. See also Cladonia.
It is an erect many-branched lichen that grows up to 8 cm (inches) high. Each branch is usually subdivided into three or four smaller branches. The colour ranges from pale green to various shades of brown-gray or whitish. Its periods of most rapid growth are spring and fall when high humidity and cool temperatures prevail. As a lichen, its body is formed from the symbiosis of one or two fungi and a photosynthetic alga or cyanobacteria; the photobiont (photosynthetic member) of reindeer lichen is a species of single-celled green algae (Trebouxia).