At first glance, you might think you're looking at Spanish moss. You're not. You're not even looking at a plant. It's a lichen. To be a little more specific, one of the old man's beard lichens. And the first thing to know about lichens is that they're actually two different organisms, an algae and a fungus, combining together to form something completely different. Taxonomically speaking, they are members of the fungi kingdom.
But if you thought it was Spanish moss, you weren't really that far off base.
Old Man's Beard is a member of the genus Usnea, a rather ubiquitous group of lichens found pretty much all over North America, and in fact, all over the world. The U.S. Department of Agriculture's PLANTS database lists about 120 Usnea species and subspecies living on the continent. They are all considered beard lichens, although they have a few other common names, including tree's dandruff, woman's long hair and tree moss. And while the specific fungi and algae vary per Usnea species, they are always from the same class, or division, within each type of organism. In other words, they're all related to one degree or another. To be clear, lichens aren't parasites; when they grow on a tree, they're using the host only as a place to grow, taking nothing in the way of food or nutrients. They perform photosynthesis to manufacture what they need to survive.
It's difficult to identify specific lichen species, so much so even experts can misfire.
Old man's beard is pale greenish-gray in color, and has long, hair-like strands, the source of their common names. The great Swedish botanist, Karl Linnaeus, creator of the binomial naming system that scientists use to identify species, thought Spanish moss looked so similar to Usnea lichens that he named Spanish moss Tilandsia usneoides, " meaning of usnea."
But it's not hard to separate the two. Old man's beard is more elastic than Spanish moss; pull it and it will stretch a bit. Pull Spanish moss and it will break. It's also finer in appearance, more hair-like than Spanish moss, and a little more unruly looking.
Like almost all lichens, old man's beard is edible, if prepared correctly.
The problem is lichens are high in acid, and the key to making them palatable is to soak them in several changes of water to raise the pH before eating. According to Eat the Weeds, old man's beard is less acidic than other lichens but still needs to be soaked first. It is high in both carbohydrates and vitamin C. Bon appetit!
Old man's lichen also has sat on the traditional medicine shelf for thousands of years, used to control fevers, as an expectorant and as a remedy for bunch of other conditions. It's has been used to dress wounds, and it is believed to have antibacterial and antiviral compounds. More recently, it's been touted as a weight control product, although there is evidence that it might cause liver damage. Usnic acid, sodium usniate, is both the key ingredient and the source of the problem.
Old man's beard and other usnea are members of Parmeliaceae, a large family of lichens.