Maybe a better question is“What are Lichens?”. I decided to use that most accessible information source: Wikipedia on Lichens whose definition says
“Lichens are composite organisms consisting of a symbiotic association of a fungus with a photosynthetic partner), usually either a green alga. The morphology, physiology and biochemistry of lichens are very different from those of the isolated fungus and alga in culture. Lichens occur in some of the most extreme environments on Earth—arctic tundra, hot deserts, rocky coasts and toxic slag heaps. However, they are also abundant as epiphytes on leaves and branches in rain forests and temperate woodland, on bare rock, including walls and gravestones and on exposed soil surfaces (e.g. Collema) in otherwise mesic habitats. Lichens are widespread and may be long-lived however, many species are also vulnerable to environmental disturbance, and may be useful to scientists in assessing the effects of air pollution,[ ozone depletion, and metal contamination. Lichens have also been used in making dyes and perfumes, as well as in traditional medicines.”
photo by Martin Lebar
Another good information source on lichens is Lichens of North America
Lichens are also a great photographic subject. The best work on lichens is Lichens of North America by Irwin M. Brodo, Sylvia Duran Sharnoff and Stephen Sharnoff and features identification keys and the photography of the Sharonoffs You can also see over 6300 photos of lichens and lichen-related topics on the Sharnoff”s Lichens Home Page. For close-up photographers, lichens are a great subject on breezy days as many species are not wind sensitive.
photo by Jacopo Werther
There are lichen workshops at the Regional Parks Botanic Garden, Tilden Regional Park, Berkeley, the second Saturday each month from 1-4pm. Meet at the Visitors’ Center. There will be a lichen workshop session at the Regional Parks Botanic Garden on August 14th, from 1pm to 4pm. Please RSVP to firstname.lastname@example.org if you would like to attend and please indicate if there is a special topic or aspect of lichens you would like to explore.