Lichens come in so many forms, how can we say “this is typical”? These lichen types or forms often intergrade, of course, but important differences in structure help sort them out. Happily, they are often grouped into basic configurations; click on the links below to learn more.

• Crustose lichens are the ones that are most often overlooked yet, sometimes, the easiest to see! Bright splashes of color on rocks often indicate crustose species. But the dull grays and browns that blend into the rock or other background, becoming all but invisible, may be lichens too!

• Foliose lichens look the most like familiar plants, and are usually larger (part of a group called macrolichens). These are often the first to come to mind when people think of lichens. They may be loosely or tightly attached to their substrates.

• Fruticose lichens may be the largest of all, and will be spotted hanging in trees or growing on bark. But not always—many of them grow on the ground as well. Fruticose means “shrubby”; you might want to think of these as more 3-dimensional forms of lichens.

• Umbilicate lichens resemble foliose lichens but have the distinction of being attached to the substrate only at one central point. They vary in size; some, like these, look like large “potato chips” attached to a rock.

• Squamulose lichens

To explore Colorado macrolichens in more detail, check out Weber’s Colorado macrolichen key, online in PDF form at AZfungi.org.

Did you know? To get very far with identifying lichens, you often need to look at their chemistry as well as their microscopic characteristics!