I was cleaning out my storeroom the other day and came across another recycled solar device that I was fooling with a few years ago. A one liter clear plastic bottle makes a good hot cap or cloche when you cut the bottom off it. Plant a seedling, pop the bottomless clear cap over it, and you protect the seedling from the cold. It probably adds between 5 and 10 degrees F over the outside temperature by protecting the seedling from the wind and by capturing sunlight in a small, closed space. My twist on this idea was to find different sizes of clear plastic bottles which could nest one inside the other making a double-glazed hot cap cloche. A double-glazed hot cap cloche might be able to protect the seedlings even better, keeping that small, closed space even warmer than the outside air.
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