Jewels of the Northwoods

By guest contributor and collections volunteer, Jan Sharp.

Have you ever walked down a trail in the woods and wondered, “What’s that white spot on the tree trunk?” or “What’s that gray-green stuff covering that dead tree limb?” 

Most likely, what you’re seeing is a lichen – a symbiosis between a sac a fungus (an ascomycete), and a photosynthesizing algae or cyanobacteria. The fungus provides shelter and nutrients for the algae or cyanobacteria, which, in return, shares its sugars with the fungus. Lichens grow on rocks, tree bark and limbs, the ground, among mosses, and can even be found on rooftops. 

This tree exhibits a healthy growth of Common Greenshield, among other
lichens colonizing the bark's surface. Photo by Jan Sharp.

Lichens have both beauty and function. They can form a thin crust on the bark of a tree or on a rock (crustose), often looking like a bird dropping. Lichens can also appear like a leafy mass (foliose) on a tree trunk or twig, or an alien-looking cluster of stalked cups or spears (fruticose) rising into the air. They provide food for reindeer and any number of invertebrates and vertebrates. They become camouflage for the Red-eyed Vireo nest. 

Lichens are the hidden jewels of the woods. Upon close view with a hand lens or macro lens camera, they reveal an almost otherworldly beauty. They thrive in cold, wet conditions, and can even survive under the snow, making them available for collection year-round. They are easy to collect, prepare, and store, taking up little space and remaining unchanged for many years – some in our collection have lasted over 50 years. 

Lichen samples may be easy to collect, as their connection to tree,
rock, or ground substrate can be disturbed by strong winds. Photo by Jan Sharp. 

In conjunction with the new Museum exhibit, Becoming the Northwoods, we are preparing a hallway display of some of the lichens commonly found in our Northwoods. I have collected some lichens from different tree limbs and trunks, and from the ground and other surfaces to be displayed as representation of our Northwoods diversity.  Some lichens are found on nearly all trees – such as Common Greenshield, which grows on many different tree barks, or Poplar Sunburst Lichen, primarily found on Aspen or Basswood limbs. Others, like Reindeer Lichen, are found on sandy, moist soil.  Boreal Oakmoss is not a moss but looks like one from a distance and can cover most of the limbs of some trees. 

The gorgeous shapes and pop of color afforded to us by
Poplar Sunburst brighten the forest on the most wintry days. Photo by Jan Sharp.

So, the next time you see a spot on a tree, take a closer look. You will be in awe of these Northwoods jewels.