A Fruticose lichen is a form of lichen fungi that is characterized by a shrubby or bushy growth structure. It is composed of a thallus and a holdfast. The lichen is formed from a symbiotic relationship of a photobiont such as cyanobacteria and a mycobiont such as fungus. Fruticose lichen is characterized by an ascending, bushy or pendulous appearance, and composed of a complex vegetation structure. While lichen communities are mainly controlled by water and light, vegetative dispersal and filamentous growth in fruticose lichen is often associated with areas of low elevation. Fruticose lichens can endure high degrees of desiccation. They grow very slowly and will often occur in extreme habitats such as on tree barks, rock surfaces and on soils in the Arctic and mountain regions.