Usnea is a generic name for a rather broad group of lichen in the parmeliaceae family. Hanging from dying or sick trees like green cotton, it is mostly called by the common names of Old Man’s Beard or Beard Lichen. Although usnea indicates the symptoms, it is not the cause of the tree’s condition. Usnea is very sensitive to air pollution, especially sulfur dioxide, which can severely impede its growth.
Usnea is believed to have antibiotic properties and was used like a sterile gauze for wounds. It is recommended to only use this plant externally. The lichen can also be used to create dyes for textiles, giving yellow, orange, green, blue, or purple hues. Click on the image for a larger view.