Likeable Lichens

Old man's beard lichen (The fruticose lichen I found in Minnesota)

These resilient fungi/alga combos come in many shapes and almost every color. They often thrive in very stressful environmental conditions and are generally a good indicator of air quality. These delightful organisms are lichens!

I have recently come to a greater appreciation of these little known fungi relatives while taking a Botany class at MSU. This was not my first exposure to lichens. I found crustose lichens inhabiting the A`a and Pahoehoe lava at Craters of the Moon in Idaho and fruticose lichens hanging from the trees in northern Minnesota. Little did I know I could find them in my own backyard…

As I mentioned above lichens are a combination of two or even three organisms. They can be cateogorized into two parts 1) a mycobiont (fungus, which can’t make its own food) and 2) a photobiont (green algae or cyanobacteria which can make its own food). Each provides a unique benefit to the other. The fungus is provided with organic food and oxygen from the photobiont and the photobiont is provided with water, carbon dioxide, minerals and protection. This relationship where two or more organisms benefit from the other is known as mutualism.

Lichens come in many different “shapes” (or more scientifically approved terminology growth forms). There are three main forms: crustose, foliose and fruticose. Crustose lichens form a crust over a surface such as a rock, soil or tree. Their entire surface is attached or embedded to the substrate. They come in many bold, vibrant, colors such as yellow, orange, red and green. Foliose lichens are somewhat leaf-like or ruffled. Fruticose lichens are more diverse in form they can be hair-like, shrubby or cup-like.

Here are a few examples of the varying types of lichens:

Crustose lichen

foliose lichen

Fruiticose Lichen (British soldiers)

Fruticose Lichen (British soldiers)

After realizing the diversity in form and color of these unique organisms I was able to find several crustose and foliose lichens on the trees and rocks in my own backyard. What an exciting find!

To learn more visit:

US forest service site – What are lichens?

Backyard Nature – Lichens

Lichen Biology and the Environment


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