Tree painted turquoise
Down the hill, close to Crow Creek, someone had splashed turquoise paint against the trunk of a big Black Walnut tree. The color looked vivid and damp. Up close, it had the texture of cotton candy.
A lichen, I suspected. Many lichens look as if they have tiny leaves. Others resemble paint. Some of the paint-looking lichens are named Lepraria, so that was my first guess. John Pearson, who knows vastly more about lichens than I do, identified the species for me. This was Fluffy Dust Lichen, Lepraria finkii.
That’s perfect.
I went back and wandered in those woods with new eyes. Besides on the big walnut, now I was seeing the turquoise “paint” on other trees too.
A closer look
I murmured an apology to a River Birch, pried off a tiny chip of turquoise bark with my pocket knife, and brought it home to the microscope. Features emerged that I couldn’t see before, tiny, soft-looking bits of… turquoise-colored dusty fluff. Fluffy Dust Lichen.
On the above photo’s scale, the numbers are millimeters. The whole image is one centimeter wide, the tip of my little finger. The individual turquoise particles really are the size of dust.
Those particles are soredia, tiny bundles that can drift away and start lichens wherever they land. Many lichens produce soredia. However, in this species, soredia are not something made by the lichen but rather they are the entire lichen. Lichens are not plants, but this is as mind bending as if a plant somehow managed to have no stem, leaves, or flowers, and was made of nothing but seeds.
And even closer…
When I increased the magnification, I could start to see minute strands of lichen, bunched into bundles. Below is a close view of Fluffy Dust Lichen. Each bundle is a soredium, containing the lichen’s complete DNA.
At this scale, the lichen appears as a misty landscape of trees. It’s like seeing a forest from the view of a high-flying bird, or looking down into an alien world. A dot from a felt-tip pen would cover up everything in the photo below.
The Iowa connection
This lichen’s scientific name is Lepraria finkii (“finky-eye”). It’s named after Bruce Fink, who was arguably the most famous botanist in the United States 100 years ago. He taught at Grinnell College, in Iowa. His special interest was lichens.
The lichen battle
Fink was one of the earliest botanists to defend the idea that a lichen is not a single organism but two, a fungus and an alga, living together in one body. Most botanists thought the idea was absurd and were outraged at the concept. But Fink’s side turned out to be right.
The pleasure of acquaintance
I’d been walking along Crow Creek for 15 years before I noticed the turquoise-painted trees. Now that I recognize Fluffy Dust Lichen by sight and by name, it almost calls out to me and waves when I arrive in the oxbow. We’re neighbors. Friends, I’d say.
I love your words as much as your photos!
Oh Diane, Thank you so much. I have been seeing and photographing that turquoise colored lichen on walnut trees this year also--and now --thanks to your article, I know what it is. Very informative article. Thanks too for the microscope photos. With a fun name like Fluffy Dust-- I should be able to remember it.