Why is it growing all over my trees and what can/should I do about it?
Lichens seattle favorite: a concise orientation before we get practical.
Lichens seattle favorite: Quick notes
As mentioned, lichens do not harm trees and actually contribute a great deal to ecosystems. Resist the temptation to pick or cut them off of tree bark which can damage the bark itself.
Increased lichen growth might be simply a sign of age. Mature, but healthy, trees tend to develop more furrows or crevices on their bark (depending on species), so lichens, mosses, and other clinging organisms have more favorable surfaces on which to get a foothold. Also, individual lichens slowly grow and increase, so older trees can keep growing happy lichens.
But increased lichen growth can also hint that a tree is struggling, if that’s not apparent from other symptoms. Reduced vigor from stress, disease, pest damage, or environment can cause trees to attract more lichen due to:
Increased light penetration: If a stressed tree loses more foliage and branches, more sunlight reaches its bark surfaces, where lichen can thrive.
Slower bark growth: Many vigorous trees continuously shed and renew their outer bark, making it difficult for slow-growing lichen to establish (except on older trees or species with naturally furrowed bark). Stressed trees have slower bark turnover, providing stable surfaces for lichen.
Reduced tree defenses: A vigorous tree produces compounds and maintains bark characteristics that naturally discourage epiphytic growth (a category of plants and plant-like organisms that grow on the surface of another plant). A declining tree may lose some of these protective mechanisms.
If you suspect that lichen growth is accelerating on your tree due to loss of vigor, the best approach is to improve your tree’s base health. This might include adding compost over the root zone, fertilizing, consistent watering, and treating any pest or disease issues.
So try to foster healthy, full-leaved trees for a long life. But enjoy those weird-looking lichens and appreciate all they are doing for us behind the scenes!
Lichens seattle favorite comes up here to connect ideas for clarity.
Tiny tip — Exactly what I needed to see today, thanks. So cozy.