I don't see anything wrong with growing on other people's land, especially if they don't use MJ ('cause that would look suspicious). If they find the patch, they have several options. They can destroy it themselves, and that's the end of it. They can report it to the cops who will come out and destroy it, maybe question the land owner a bit, then that's the end of it. Or they can leave it alone because they used to be a hippie back in the 70's or something like that, and that's the end of it.

The police cannot convict anyone of a crime without evidence, and if someone doesn't know ganja is being grown on their property, there's a pretty damn good chance there won't be any evidence to convict them of a crime.

I'm growing on someone elses land, and if the worst should happen and they get arrested for it (I would probably hear about it in the newspaper or through the grapevine or something) i would probably go turn myself in and free them of any penalty. The chances of this happening are so remote that i'm not even worried.

Bottom line, i don't think there's any solid ethical principle that decides this issue. Growing is illegal whichever way you look at it, and thus unethical. Determining how unethical something is almost seems like a waste of effort. You have to determine for yourself whether you're willing to break to law and grow pot, like a yes/no question, then determining where is simply multiple choice.

My humble opinion...