No offense, but you sound like an easy target. Those rippers would hurt you. They take the risk of getting hurt while ripping you. It's the game, and if your not willing to use force, they will walk all over you. They will be back next year, hope your ready.
I hope I am wrong, but criminals don't care about hurting other people. They only care about themselves, and need an eye opening experience. An alarm being tripped isn't going to do anything unless you follow up with force. Also, it's not brain surgery to disable the electricity out to a greenhouse. I would advise non powered deterrents as well. Such as trip wires with 12 gauge rounds.
Hope those losers are in jail this time next year. Where they belong.