Lichens can be divided into three types. Crustose lichens lie flat on the substrate and are the most tolerant of pollution. Look at any young maple or beech tree and you will see this lichen. Foliose lichens have a flat but leaf-like structure. Fruticose lichens are free-standing like Usnea or ‘wrinkled lettuce’ (my name) lichen. The latter two are most sensitive to air pollution and are often found at the tops of trees, the limbs falling to the ground in high winds. Lichens can be seen in various colors -yellow, orange, red, purple, brown, etc. These colors are due to the presence of a special pigment-containing usnic acid. Most lichen species grow best where there is sufficient light and moisture within a moderate temperature zone. However, some lichen species are very adaptable and hardy.

When left undisturbed, lichens live in many varying climates and altitudes throughout the world. Some species can survive the most unfavorable climatic extremes of the arctic, alpine, and desert regions by reducing metabolic activity for extended periods of time. Yet individual species may only exist within a restricted habitat or geographic range. Most lichens are sensitive to air pollution in varying degrees, and like canaries in coal mines, may serve as indicators of air quality.

Most fungi that form lichens produce microscopic spores in sacs. A fungus can produce millions of spores sexually. A new lichen association can be created only when fungal spores come in contact with the appropriate algae or cyanobacteria in the right habitat.

Lichen reproductive parts containing both algal and fungal cells may also occur asexually for dispersal. In vegetative reproduction, any fragment or shred of lichen containing both the algal and fungal components that break off the original can form a new lichen body.

This winter, though just beginning, has been hard on trees because all have been weakened by logging, insect damage, extreme temperature changes, and other effects of global warming. With so many broken and severed limbs on the ground, it is easy to see that many are covered with lichens. I have already collected enough Usnea for this year’s medicinal tincture, something I normally don’t do until spring. My balsam wreaths are festooned with two species of Usnea and Fringed (‘wrinkled lettuce’) lichen. Every few days I soak these in warm water, so they don’t dry out (I love the shades when they are wet). In the spring I return them to the wild. My terrarium has a few Fringed lichens, tangles of Usnea, and a bit of Lungwort I found on the ground in my favorite forest after an animal had eaten most of what had been a large, rounded lichen.

As a fruticose lichen, Usnea appears as a shrub-like growth on host trees. Unlike other similar-looking fruticose lichens, species in this genus have an elastic chord or axis running through the middle of the thallus that can be revealed by gently pulling a filament apart from either end. In a healthy forest, this lichen often cascades in clumps from bare branches, a beautiful sight. Based on a fossil found in amber, Usnea was present about 34 million years ago. Many animals love to eat this lichen (as well as others), so it is an important food source for wildlife.

The only place I have found Lungwort (Lobaria pulmonaria) is in my favorite forest; one that has been left to rewild itself. Lungwort likes humid forested areas with both maturing or old conifers and hardwood trees. It used to be quite common in its ideal habitat, a shady environment, quite literally ‘flowering’ from trees and rocks. Finding this lichen indicates rich, healthy ecosystems with very clean air. Lungwort is large, bright green, and leaf-like. The green algae give it its startling, almost emerald appearance… attached pockets of cyanobacteria (blue-green algae) are darker in color – a drab gray – and appear in sharp contrast to the green. In this forest, I have found a number of healthy specimens, some quite large and round, but sadly, in general, this lichen is becoming scarce, an indication of too much air pollution in Maine.

Green Shield, a foliose lichen is easy to spot on trees, especially on a cloudy day. This lichen is more tolerant of air pollution. Just this morning I was looking out my window towards the brook and could barely see any lichen because the sun was shining. A few days ago, it was cloudy, and lichens were visible everywhere I looked. I took a photo of Green Shield lichen on a healthy maple tree about 20 feet up and was amazed to discover that in addition to the one I photographed, there were about 8-9 other lichens I hadn’t seen previously! Some I have not yet identified. All were growing in a roughly 12 by 12 area. When I counted all the lichens and the sheet moss growing together a new question popped into my head: Why do different species of lichens grow together and why include mosses? Lichens apparently choose community living. And because lichens and mosses were the first organisms/plants to inhabit dry land, maybe they like growing together. Pure speculation. I have no idea, but I want an answer to this question! Of course, needing a
similar habitat would be one reason for clustering, but I have a sense that there is more to it than that.

The last lichen I will mention is one that grows on top of a rounded stone that looks like a mountain top. It could be Peppered Rock Shield because this cluster likes the sun. What I love about this lichen is the way it is slowly spreading over the ‘mountain’. Until the summer heat strikes it, is a beautiful luminous sage green with nubbly skin. This lack of certainty on my part brings up an important point. Lichen hunting takes discernment, time, patience, and a willingness to revisit lichens frequently, and at different times of the year, always with a critical eye. I think it’s fitting that I should end this lichen saga with one I am unsure of because, with lichen, one is always a beginner! I will be watching this one more critically this spring and summer when I am once again roaming through my favorite forest…

Before closing, I am listing some other benefits of these ancient and complex organisms:

• Lichens that contain cyanobacteria can fix nitrogen
• Lichens cover eight percent of the earth’s terrestrial surface
• Lichens provide food for mule deer, whitetails, mountain goats, pronghorn antelope, northern flying squirrels and other squirrels, voles, wild turkeys, slugs, snails, mites, springtails, and certain caterpillars, to mention just a few
  animals.
• Lichens provide nesting material for 50 species of birds, especially hummingbirds
• Lichens provide protection and background camouflage for lizards, certain moths, and tree frogs. Lacewing larvae cover their wings with lichens
• Lichens are sand and soil stabilizers (especially in deserts – I witnessed this with a dark brown crustose lichen in NM)

I hope I have captivated a few peoples’ imaginations and encouraged them to meander through our winter forests…
Happy Lichen Hunting to those who do!

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