Fuzzy Trees – what is a lichen?

Throughout the year the oak and pine branches here in the northeast (of the USA) explode with a greenish fuzzy growth in times of rain or extended dampness. This actually happens pretty much all around the world in some form or another. There are epiphytes, mosses, orchids, ferns, and lichens that grow in and on trees. They are not connected to the ground and most of them are not parasitic. They just live in treehouses; gathering moisture and stuff from the air around them.

This fuzzy plant-like growth that I am writing about is a lichen – a Usnea to be exact and probably Usnea strigosa. This is a very common “plant” in most parts of the east and northeast of North America. It attaches to the bark of trees, or sometimes to dead wood, where it simply hangs out month after month and year after year. It belongs to a group of lichens called fruticose lichens and is related to a vast array of similar lichens found world-wide. Many of this group (the Genus Usnea) are called “old mans beard” or “bushy beard” or some other phrasing that would remind you of a shaggy beard. (“Spanish moss” is another common name for a plant that hangs from trees; but Spanish moss is a Tilandsia – a cousin of the pineapple and is a flowering plant not a moss or a lichen.) The group apparently can be used medicinally to control weight, pain relief, wound healing, and as an anti-bacterial agent – though I have no idea how it is prepared, used, or collected.

Lichens are not a real thing! There are at least 14,000 organisms that are called lichens that have been identified worldwide – and they still aren’t a real thing! They look like a moss or like a fungus or maybe just a scaly thing on a rock. What they are, and how they are named, is based on the sort of fungi (usually an Ascomycota – a group of about 30,000 similar fungi) and not so much on its photosynthetic partner. The usual cohort is an algae but there are lichens that use Cyanobacteria (blue-green algae) as well. The relationship has been called symbiotic but the actual relationship is much more complex; growth and reproduction of the photosynthetic part of the lichen has to be somewhat unlimited – so the fungi aspect of the relationship takes the fruits of photosynthesis but allows the green portion to grow and reproduce.

But the more you know about plants the more you realize that fungi are integral to the lives and growth of many many plants – from the lichens through the giants of the forest. Fungi provide the mechanism for transfer of minerals and moisture from the soil to the plant. They seem to be the IV tubes that allow plants to gather goodies from the ground (and maybe from the air).

Perhaps everything is a lichen to one degree or another.

Here is a small dish of Usnea strigosa that fell during some recent wind and rain. As the lichen often grows on dead branches (it isn’t a parasite and can grow on anything) it is common to find small branches and bits of “beard” on the ground.
There are few common names for the various parts of mosses, fungi, and lichens. We don’t talk about them enough as a culture to have developed nice little botanical terms like leaf, branch, trunk, or bark. Part of it is that these organisms are different – the thallus is a stem sort of but it also does much of what leaves do and it connects to a “holdfast” as there are no roots in these Usnea growths. The rounded, hairy-edged thing in this picture is a fruiting body called the apothecium and it looks sort of like a leaf (but so does all of the plant); its most important role its to house/hold/display the fruiting bodies of the Usnea called asci. It has no more of a leaf-function than does any other part of the lichen.
This group, and most fungi, are in a very special linguistic arena.
This is a small clump of Usnea strigosa on a branch in the rain, on a gray and gloomy day. The outside temperature is about 40 degrees Fahrenheit and the woods is a hazy gray-green as almost all the trees are hosting a blush of Usnea. The fungi/lichens will dry out and pretty much disappear in arid times and expand and grow in times of wet weather – even in cold wet weather.

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