A lot of people get nervous when they see tons of flowers on their pumpkin vines and no fruit, but rest assured you are right on schedule. Right around mid-summer, pumpkins will usually start to flower in large numbers. But this is only half of the pumpkin-making process. These early bloomers are just the pollen-producing male flowers. Male flowers tend to have smaller stems and grow farther away from the main stem of the pumpkin. (see below)
Several weeks after the male flowers bloom, the female flowers will start to form. These can be identified by little bump just behind the flower. This is actually the ovary from which a new pumpkin will grow. (also see below)
Like all members of the cucurbit family, including squash, cucumbers and zucchini, pumpkins are bee-pollinated. As they forage for food, bees transfer the pollen from the male flowers to the female ones. Once the female flowers are fertilized, the pumpkins will start to grow.
To encourage bees to visit your pumpkin patch, try planting some bright flowers nearby to attract them. Lavender, cosmos, bee balm, black-eyed susan, salvia and blanket flower all make great companions for pumpkins.