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What does this Old Man's Beard have to do with the forest?

What is that grey, stringy stuff on the sides of the trees in the forest? It looks almost like light green hair. Also known as Old Man’s Beard or Tree Moss, this lichen is named Usnea. It grows on the sides of trees, on rocks and even directly on soil, almost all over the world. There may be one exception. Apparently, Australia doesn’t have much, if any.

Although lichens like usnea may appear to be a single plant, they actually consist of both algae and fungi. The alga and fungus grow together in a symbiotic, mutually beneficial relationship. The fungus provides the structure, mass and protection from the elements and the alga produces nutrients for both itself and the fungus.


The way to distinguish Usnea from other lichens that need similar environments is to hold a strand in your fingers and gently tug on either end. The outer green sheath will split, revealing a white inner pith that will stretch before snapping. Usnea is elastic; other lichens aren’t.


It has long been used in traditional medicine. The ancient Greek physician Hippocrates is believed to have used it to treat urinary ailments, and it’s regarded as a treatment for wounds and inflammation of the mouth and throat in South African folk medicine. Usnic Acid and polyphenols, the main active ingredients in usnea, are believed to provide most of the alleged benefits of this lichen. Pure Usnic acid can destroy your liver, so great care must be taken when using usnea as a long-term treatment for an ailment. Also, heavy metals are likely to accumulate in Usnea, another reason to be hesitant to use it long term. Although usnea is purported to have all sorts of positive medicinal value, few of the claims have been supported by modern day science. The usnic acid in usnea may promote wound healing. Some research has shown that usnic acid has antibacterial properties and may reduce inflammation and promote wound closure. More human studies are needed to determine how much usnea is effective and how it should be prepared.

Many gardeners ask if the usnea is to blame for killing a tree. Usnea often will grow on a sick or dying tree because that tree has lost leaves, allowing more sun to reach the lichen’s algae. The lichen is benefiting by the tree’s loss of canopy, but is not a cause of the loss of leaves and sickness.


Interestingly, another use of usnea is as an environmental indicator. Usnea is extremely sensitive to air pollution. In areas with extreme air pollution the lichen may be very tiny or not be present. When usnea is healthy it can be a foot or more long. It will only grow this well where the air is clean and of high quality. It is very sensitive to acid rain and sulfur dioxide, both the result of burning fossil fuels. Usnea tends to only grow in those regions where the air is clean, and of high quality.

Many years ago, I was taught that if you get wounded in the wilderness and you are losing blood, you should pack the wound with usnea. It would help the blood clot and delay infection until you could get to a medical facility. Carrying some basic first aid supplies when you hike is probably a much better idea. Antibiotic cream and band-aids come in very handy on a long hike.


As you hike along the double loop trail in the Joyce Kilmer Memorial Forest, you should see lots of usnea growing on the trunks and branches of trees. It will be growing during all the seasons of the year. It is a wonderful indicator of the improvement that has been made to the air quality of this area.

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