Curious Pumpkin Mating Habits
Pumpkins produce both male and female flowers on the same plant. It’s interesting to note that the first flowers you see on your pumpkin are male, and bloom and die within a very short period of time. The male flowers serve to attract pollinators such as bees.
When the male flowers have died off, they are replaced by the female flowers. By the time the female flowers appear, pollinators know where to look for the blossoms and return with the male pollen to the female blossoms. To identify the male flowers, look at the base of the stems. If there is no bulging present at the flower base, they are the male blossoms.
Members of the genus Cucurbita can indeed cross-pollinate, but generally within the same species. For example, a Butternut and a Turban Squash could cross-pollinate as they are both from the species Cucurbita maxima. If you have several varieties of pumpkins from the same species, this cross-pollination will not produce unusual varieties during the same growing season. However, if you keep the seeds for planting next year, you might see some strange colors and shapes the next growing season.