Hey dude, I know what your going through. I let an old friend move in to my house for a little while as well. He was a nice guy, but was always moving around and mooching. I felt bad for him, and let him take the guestroom but i layed out the rules, and also gave him CHEAP rent to pay. He was good for a month of so, and then after that one day I came home to a party of 40+ people. I kicked everyone out, and he freaked. He wasnt even coked up, he was just an idiot.
What i didnt realize, is that he had minors at the party. Sure enough, the next morning, a few of the minors told their parents about the party. At 11AM there was a knock on the door from the local PD who could tell that I was cleaning up from the night before. I let them in the foyer, talked to them a little bit, and told them what happened. I figured, i had nothing to hide - and I didnt invite the minors so they should understand.
Turns out that some of the parents decided to press charges and because it's MY house, I was completely at fault, even though i wasnt home. Of course, my roommate completely ditched, and didn't pay me the 2K+ that he owed me.
Long story short, I hired a lawyer, and over $8,000.00 in fees later the charges were dropped. Just comes to show there is only ONE person you will ever be able to trust - yourself. So not just in this situation with your plants, but with everything - don't trust people. Your a nice guy, I'm a nice guy, but nice guys get fucked over. If people know you are nice they will take advantage of you.
Look out for #1 Bro, and good luck!