I know someone who was caught... but he had gotten mixed up in the nasty shit... nose candy... keep on with your small garden, keep your mouth shut, don't deal where you grow, and stay the FUCK away from hard drugs, that Leo is oh so interested in.
As for penalties, it's up to you to find out how your local laws are written. 3 plants is often a very simple plea. Personal use, experiment, blah blahblah...