How should an indoor window box be built?
Make indoor window boxes 6 inches deep; the width and length to fit a windowsill. Provide one 3/4-inch drainage hole for every 100 square inches of bottom surface, if you can make some arrangement for catching and disposing of the runoff water. Otherwise, put 2 to 3 inches of gravel in the bottom. Construct the box of redwood or cypress to prevent decay.
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