Answer: Bottle gourds can be harvested when they're fully mature, usually after the first frost in your area. Mature gourds have hard, light brown shells. Take them indoors and allow them to cure for several months in a cool, dry place until you hear the seeds rattle inside when you shake the gourd. Then drill a 1" to 2 1/2" hole in the side of each gourd: make the smaller sized hole for birds like wrens and the larger sized hole for large birds like martins. Also drill a few small holes in the bottom of the gourd for drainage. Then drill two more holes in the top and thread nylon fishing line or light-duty wire through these holes so you can hang the birdhouse. You may want to varnish the gourd before you hang it, to keep it weatherproof. Untreated gourd birdhouses will last about two years.
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