A couple weeks ago I was hiking with a group of people, including my sister, and I was talking about lichen, the green stuff that grows on rocks and trees, and she thought I was talking about werewolves. I was SO confused, but it turns out that there is a popular show with a species of werewolf characters called lichen. I don’t know why they would name wild ferocious mythical man dogs after the lovely peaceful fresh air loving lichen! Sometimes I just can’t keep up! So for all of you out there with adolescents or pop culture lovers in your life, who may also be thinking that lichen is a type of werewolf, today’s post is for you!
I have been wanting to write a post on lichen for seriously a year, but I also wanted to get some pretty photographs of really healthy lichen, so finally, as I say goodbye to my Blue Ridge Mountains and head back to Florida, I celebrate the not hairy or scary organism known as lichen. At the risk of revealing my plant nerdiness, I have liked lichen since I was a child. One summer at camp I won the prize for knowing the most about lichen in the end of camp nature trivia contest! I wish I could remember everything I knew when I was 8, but I can say wonder fueled natural history knowledge which in turn kept my wonder for lichen alive into adulthood. Success.
Lichen grows when certain algae and fungi join in a symbiotic relationship. In certain species the fungi and the algae can live independently of each other (not joining to form lichen), but in other species the fungi cannot survive without its lichen partner. They grow slowly and spread when bits of their “bodies” break off and land in a new place.
There are 20,000 types of lichen with more being discovered and the species has been around 400 million years! The lichen that I am most familiar with are the temperate epiphyte variety that cling to rocks and trees. They can feel velvety or scratchy, come in a variety of colors from green and gray to reds, browns, and yellows. I think are so sensorially interesting.
Lichen will absorb some minerals from the surface, but are generally self sufficient and do not hurt the host.
Lichen can be found in many climates from the arctic tundra to temperate (as the lichen in these pictures) to the tropics and desert. Lichen do not like to be in soaking standing water for any period of time, but they can completely dry out or be covered in snow as you see in my pics.
Here’s the biology and lichen anatomy for you science teachers: “Lichens occur in one of four basic growth forms:
- crustose – crustlike, growing tight against the substrate.
- squamulose – tightly clustered and slightly flattened pebble-like units.
- foliose – leaflike, with flat sheets of tissue not tightly bound.
- fruticose – free-standing branching tubes.
The bulk of the lichen’s body is formed from filaments of the fungal partner, and the relative density of these filaments defines the layers within the lichen.
At its outer surface, where it comes in contact with the environment, the filaments are packed tightly together to form the cortex. The dense cortex serves to keep out other organisms, and helps to reduce the intensity of light which may damage the alga cells.
The algal partner cells are distributed just below the cortex in a layer where the fungal filaments are not so dense. This is very similar to the arangement in a plant leaf, where the photosynthetic cells are loosely packed to allow air circulation.
Below the algal layer is the medulla, a loosely woven layer of fungal filaments. In foliose lichens, there is a second cortex below the medulla, but in crustose and squamulose lichens, the medulla is in direct contact with the underlying substrate, to which the lichen is attached.” UC Berkeley
Lichen have had many uses throughout history including as a food source for foraging animals, a source for some medicines, natural dyes, perfume and soap scents, in decoration and hobbies (reindeer moss), and are used to dye litmus paper. They also do the important work of making soil. The lichen on rocks help break the rock down into tiny pieces over time which contribute to new soil. Environmentally, lichen are important watch dogs of pollution. In polluted areas you will not find lichen or it will die if the air becomes too polluted. So where you find lots of lichen, breathe deep and relax! The air is great! (and there are no werewolves!)
Now get outside and go explore some lichen for yourself!! It will be more interesting than you expected!
What overlooked or misunderstood part of nature is your favorite?
Share in the comments below!
Seeds to Sprout:
Learn more about and see pictures of the Lichen of North America
Check out this Awesome Eat the Weeds post on edible lichen (not so appetizing) and its other historical uses.
An academic look at the ways indigenous people of Canada ate and used lichen, when food was scarce. (scroll down until you see the subheading for lichen)