Well, covering them at night will protect against the cold, but you'll still have to lengthen the hours of light or the plant will think its season is done & over & die during the shortest days of the year. If you can cover with say a huge trash can & put a cfl in there too, that would work & your neighbors wouldn't see it at night. But remember, you'll have to do this untill May. (Take the can off during daylight hours). Does that seem do-able for the size/ location of the plant? If the size works, but you still need to hide in the day too, Wheeze sugested cutting a window in the south side of the can & covering the hole you just cut with clear plastic wrap. (I think that was in one of the deleated posts). If you can manage to make this work, by next harvest you should have an even larger harvest than this years.