Gourd vines have male and female flowers. The male flowers appear first. The difference between the two is that the female flower has a small gourd shape beneath the petals. The main vine is the one that grows first, and has more male flowers than female. The main vine should be cut to about 10 feet long. This encourages more female flower growth. I hand pollinate the gourds I use for my artwork. You can do this by picking the male flower and bringing it to the female flower. Using a paintbrush is the easiest. Pollen can be transferred by brushing the stamens (pollen) on the male flower, and tapping it into the female flower. Make sure that you get enough pollen to ensure pollination. Then take a rubber band and band off the female flower so no insects can get into it and cross pollinate. Also, some gourd vines I will cut off all gourds except one. Usually on the bushels, or Giant African bottle. Doing this makes sure that all nutrition goes to that particular gourd.