[Baz]

I'd have a talk with the kid...tell him to remove the plants from your property and never ever do something like that again.

Or you could dispose of them......and still have the talk. He needs to know asap that you found his stash.

You can have a talk with his dad (optional) depending on how remorseful the kid is and depending on how close your relationship with the dad is.

Those are my thoughts.