Building A Mini Green House :: Protecting Plants During Winter

We have had a weird winter here in Northern California this year.  One day it is freezing, the next day I am sweating.  After a long summer of working in the yard and taking care of plants, when it finally got cold this year I became very depressed to see my plants start wilting.  My florist mother tried to reassure me that it was normal and okay but I still was very upset.  So much hard work…only to see it all slip slowly away…So my sweet and resourceful husband built me a mini green house.  We built a temporary covering over a grapefruit and avocado plant we recently planted.   We wrapped the structure with thin plastic protective covering used for catching paint spills (found in the Walmart paint section) so that the sunlight could get in but still protect it from frost.  We stuffed all our porch and backyard plants in as well.  I have tried checking on them a few times but it is too painful for me to look at…I don’t even want to deal with it.  Praying they will make it to the Spring.  All this to say…I was a happy girl.  It is all a learning process and I am just happy I don’t have to look at sad plants anymore!
How do you protect your plants in the winter?