What are lichens?

Lichens are not mosses. Lichens are classified as fungi.

A lichen is a symbiotic relationship between a fungus and a cyanotic bacteria and an algae.

They work together in symbiosis, the fungus supplies the protection from uv rays and can store water, the bacteria and algae produce their own food through photosynthesis with the sun and provide the fungus with sugar for growth.

There are 3 kinds of lichens, fruticose,Foliose and Crustose


More than 15.000 species have been documented up to date.

Fossil records date back to 400 million years!

Most Lichen’s growth habit isvery slow and they stick closely to solid sufaces like rocks, stone walls, grave stones, sidewalks, even leather and plastic.  Others prefer, tree trunks, branches, leaves and soil.

They tolerate extreem conditions,they are  found growing in the frozen North, at high altitudes and in hot desserts.

The very first lichens were thought to have grown on rocks near water where after a long period of time they decayed and would break down to form soil

and provided sustenance for other plants to grow on. Their metabolism can go into suspension for a period of time and can be revived when conditions improve.

Lichens are epiphytes, they need support to thrive, there can be many different varieties on one tree or even one leaf depending on the environment.


As lichens mature small pieces (filaments)and some spores may be blown  away by wind or insects and produce new lichen provided they land on a suitable algae or bacteria.



Scientists are using lichens which are sensitive to changes in the environment to test for pollution(sulphur dioxide) ozone depletion and metal contamination (mines) ,some lichens absorb radio active cesium.

Lichen are indicators of air quality! Most thrive in only pure clean air! Other species only grow near roadsides and absorb pollutants.

Very few lichens are toxic ( Letharia , wolf lichen and Vulpicida) it was used to kill wolves, it was stuffed into cavities of bait

Compounds in species like Usnea, were used by early humans as  natural antibiotics.

Lichens are a winter survival food for herds of Caribou.

Birds use lichens to camouflage their nests.


There are some fantastic samples growing right here on our trails and in our gardens. I hope you are “lichen” this article and you will find some on your next walk!