Usnea grows abundantly on trees at the north end of the Native Plant Garden; in the wild it's widely found on conifers and hardwoods. It is pale green and soft (and U.cornuta is bushy). Pull gently to break a main strand, and you'll see a tough white elastic central cord inside. It often has short branches perpendicular to the main branches.
Another common species of Usnea is U.longissima, which hangs from tree branches in beautiful strands up to four feet long.
With its usnic acid and antibacterial and antimacrobial properties, Usnea has long served medicinally. It's used for fever control, pain relief, and wound healing; it treats lung and urinary infections. As with other lichens, avoid picking it directly from trees, since it serves many creatures as food and nesting material. There's plenty to find on the ground.