Someone asked what is frost cloth. The product sold here in Arizona is a white, non-woven paper that seems to have a slight plastic coating, just enough to make it waterproof. It transmits 70% of the light so it may be left on plants for a number of weeks if necessary. It can usually be purchased at hardware stores, nurseries and agricultural supply stores. It is unavailable now from most outlets due to demand. It can be bought either pre-cut or like fabric in pieces from bolts 12 feet / 3.8m wide. It provides 2-4 degrees F of protection alone; much more if lights be placed underneath. It blows off easily if there be wind. It must be supported above the plant or portions of the plant touching the frost cloth will freeze. Some people use burlap, which is coarsely-woven jute. I think it permits too much cold air to enter and frost cloth is much better. Here in metro Phoenix we will wind up with 6 consecutive nights below freezing. Monday morning the temperature in my driveway was 20 F /-7C. My winter-growing bulbs and bulb seedlings really don't seem to mind even though unprotected. I have all the tender summer-growing stuff inside. Leo Martin Phoenix Arizona USA