Apple gourds look like a giant apple when they are mature. They are a type of Cucurbita gourd. You can carve out apple gourds to use as a birdhouse, or use them for purely decorative purposes. Like all gourds, apple gourds are slow growing, warm-season vegetables that take about 90 to 100 days to fully mature. Start the seeds indoors about four weeks before the set-out date to give them a head start.