Purple martins are swallows that live in North America. Dried gourds are commonly used as birdhouses for Purple martins, and are fairly simple to make. Large gourds provide the best housing for Purple martins because they allow for deep nests and are difficult for predators to get into. The easiest way to dry your gourds is to leave them on the vine. Any gourd that has a diameter of at least 9 inches can be dried and made into a Purple martin birdhouse.
Leave your gourds to ripen on the vine, watering them regularly until the plants are mature. Leaving gourds on the vine prevents them from softening or rotting, which is a common problem if gourds are harvested before maturity and dried indoors.
The vine and surrounding plants will die and turn brown before the gourds are dry. Leave the gourds outdoors through rain, frost and even snow; the weather will not affect the drying process.
Check the gourds for dryness after three or four weeks. Dried gourds will feel light and the inner seeds will rattle when you shake the gourd. Some gourds will take up to three months to dry, so leave partially dried gourds outdoors and check them for dryness every few weeks.
Cut the gourd's stem to remove it from the vine once it has fully dried. Use scissors or gardening shears to remove the stem a few inches from the gourd.
Clean the outside of your gourd with warm soapy water. The outside surface will probably be covered with mold after weeks of sitting on damp ground. This mold will not hurt the gourd or affect the drying process, but should be wiped away before you make your birdhouse.