They are hungry monsters that will devour everything in their path - and there are only two reasons they haven't wiped entire cities off the map.
First, their path is very predictable: up.
And second... they move very, very slowly.
As a result, trees only devour stuff left on or against them for years at a time - like this bicycle-eating tree on Vashon Island, Washington.
The tree grew around the bike, eventually lifting it off the ground completely.
These days, the bike is six feet up - and getting a little higher each day, earning it a spot in the new edition of the Ripley's Believe It or Not! book, Dare to Look.
Lesson: Don't leave your bicycle leaning against a tree. Probably shouldn't live kids or pets there either.
And if you really want to be safe, chop 'em all down.
For more stuff eaten by trees, check out this photo collection on Flickr.