Lichens are a complex symbiosis between algae and fungi, with the fungal hyphae providing structure and the algae’s photosynthesis providing nutrition. Lichens have no roots but are attached to the surface of rocks, cliffs, trees, or directly on the ground. They grow slowly and can be several metres long and very old. Many species are sensitive to air pollution and are, therefore, indicators of clean air or changes in air quality. There are about 2,100 different species of lichens in Sweden and at least 18,000 species worldwide.
Lichens are sometimes mistaken for mosses. A classic example is reindeer lichen, or “star-tipped reindeer” lichen as we call it, which we commonly refer to in the trade as white moss. However, it is not moss but lichen and is used in Christmas decorations, among other indoor and outdoor decorations. True white moss is green or reddish and grows in damp woodland. Star-tipped reindeer lichen grows on dry ground in coniferous forests and is also an essential part of the reindeer’s diet.
Sources
Britannica – Lichen 
Visaskogen – Lichen – a symbiosis between fungus and algae
Arizona State University – Biodiversity Knowledge Integration Center – Lichens
April 2023, TÄNKOM | Revised February 2024 RETHINK
