To use the twig lichen identification guide, follow the step-by-step questions and try to answer as many as possible. If you don't know the answer to a particular question, just leave that question blank. Once you have submitted your answers the guide will search the database and suggest one or more lichen species for you to choose from. By looking at the photos and information for each lichen you should then be able to make a firm identification.
The most useful features in lichen identification are colour, surface texture, and how the lichen reproduces. Some of these features are difficult to see with the naked eye so you'll need to use a x10 magnifying glass or hand lens (indicated by in the guide).
Colour in lichens often varies, particularly with the amount of sun or rain. For example, orange or yellow lichens that grow in shade may appear green, while grey lichens can appear green when wet. If you're not sure wet the surface of the lichen and recheck the colour.
Reproduction provides the most reliable characters for identifying lichens. This can either be sexual reproduction with fruiting bodies (apothecia), or asexual reproduction, where finger-like outgrowths or sugar-like granules (isidia and soredia) break off to start new lichens.
The identification of some lichen species can be confirmed in the field by a spot test with bleach. This is indicated in the guide by the symbol + red or orange. For the bleach test, simply scrape away the upper surface of the lichen, add a small drop of household bleach (eyedropper bottles are ideal) and watch the reaction. Organic compounds in some fungal partners will turn the bleach red or orange, while others have no reaction at all.