The kid who plays Vincent Crabbe in the "Harry Potter" movies could be heading to Azkaban wizard prison soon -- he just pled guilty to growing magical marijuana plants inside his mother's London home.

Jamie Waylett -- who plays the school bully in all six "Potter" flicks -- was popped in April after cops found eight bags of weed in the car in which Jamie was riding. Cops then searched Waylett's mom's place and found 10 pot plants.

Waylett will be sentenced on Tuesday -- he faces up to 14 years in the slammer.