When an owner of a dog takes it for a walk, bags up the dog shit and throws it into a tree where it proceeds to dangle from the branches, therefore producing shit trees. Usually found in rough estates around the UK.
To be so concerned with specifics or details that the larger problem, situation or point is missed. Alternate: can't see the woods for the trees. Often said incorrectly as "can't see the forest THROUGH the trees." (English, circa 1500's)
A: I hate the piss and crap all over the place from my wife's cats!
B: Dude, she only has the cats because she knows you hate it and is trying to drive you out. I guess you can't see the forest for the trees.