An accused serial tree mutilator in Brooklyn is too cuckoo to stand trial, officials said yesterday.

A psychiatric report on Steven Maynard, 36, found he’s mentally unfit to defend himself on criminal-mischief charges for his bizarre rampage, officials said yesterday.

“He’s incompetent to help his defense,” a prosecutor in the case said.

The loony lumberjack allegedly went off his meds and used his bare hands to rip branches from trees on Eastern Parkway and in Prospect Park, doing some $200,000 in damage.

When he was nabbed last month, he told cops that “there are demons in the trees, and I had to cut them down” because the demons had killed someone called “Amy.”

Maynard will be held at an upstate psychiatric facility until he’s ready for trial.