07/15/2026
https://www.facebook.com/photo.php?fbid=1009911765128074&set=a.832057576246828&type=3
For three years you've been Googling tree diseases, convinced that gray-green crust on your oak is slowly killing it. Put the phone down. That's a lichen, and your tree isn't dying — it's passing an inspection you didn't know it was taking.
A lichen isn't one thing. It's two organisms living as a single body: a fungus holding the structure and an alga making the food. Apart, neither survives this way. It's not a moss, not a fungus alone, not a disease.
And it doesn't touch the wood. It clings to the bark surface the way a sticker clings to a bumper — no roots drilling in, no nutrients stolen, no decay. If your tree really is struggling, look underground at drought or compacted soil. The lichen just happened to be watching when you noticed.
Best part: it can't survive dirty air. Its presence certifies yours is clean.
Don't scrape it. It's the proof.