free green house heat!
ok this is a method they use to grow in the high altitude green houses in the mountians:
1. paint your back walls a dark color to absorb heat during the day
2.take empty 2 liter soda bottles paint them flat black and fill them with playground sand ,pack tightly! hang these any where you can that they will not shadow the plants you are growing ,they will absorb heat all day and slowly radiate it through the nite .sand works better than water!
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