What Are Lichens?

What Are Lichens?

Lichens are plants without roots, leaves, or flowers. Even though they have no leaves or flowers, they can be quite attractive and range from a pale grey or whitish color to bright green when they are moist.

There are about 16,000 species of lichens, and they are found in every conceivable kind of place. They grow in sun-baked deserts and on exposed Antarctic rocks.

They grow in waste places, on bare rocks, bare soil, dead wood, and tree bark, and can live through heat, cold, dampness, or dryness. About the only place where they do not thrive is near a city, where they are killed by smoke, dust, and coal gas! Lichens are really two plants growing together- a “fungus” and an “alga“.

The greater part of a lichen plant is greyish, thread-like fungus material. Held among the fungus fibers are bright green cells of algae. Algae, being green plants, can make their own food, but the non- green fungi cannot.

Lichen fungi use food made by the algae. The algae use water absorbed by the fungus, which also shelters and supports the algae. Such a relationship where each member benefits from the other are called “symbiosis“, from Greek words meaning “life together”.


Lichens grow very slowly but live a long time. Some colonies are thought to have lived as long as 2,000 years! In some lichens, the fungus produces spores.

But most lichens are reproduced by broken-off bits blown or carried to new places, or by special structures that break off easily and become new lichen plants.

Lichens are the first plants to grow on bare rocks. They loosen rock particles, and these particles plus decaying lichens form the first thin layer of soil on which other plants can grow.

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