is it in a green house? I expect not right? anyways yeah ya can't just put a blanket over them... plants need to photosynthesis in order to produce energy to survive. marijuana plants are an "annual plant" . thats how mother nature created them ... as sensi said they are a bitch to keep alive over winter. I would recomend taking some clones if possible and trying to keep them alive rather then the whole plant.. where do you live?