usnea lichen can only grow in ecologically clean places on planet. spruce tree that died from pests is covered with usnea

usnea forest lichen barbata beard trees environment botanical branches flora exotic moss hang light green lichens texture nature wilderness fungus branch twig hanging wild tree landscape mountains wildlife trail laurel native bush filipendula life ecology pine fir barbate ascomycota covered lightgreen soft harvest farming agricultural horticulture dry bark pines plant