Successful pumpkin fruit set is cause for celebration. It means the female flower at the bottom end of the tiny pumpkin has been successfully pollinated with pollen from a male flower. Specifically, proper fruit set is confirmed by observing growth of the baby pumpkin.
Don’t break out the champagne just yet. There’s a long period of growing and ripening before you harvest these bright orange orbs.
The definition of “pumpkin fruit set” means a female flower was successfully pollinated, and the fruit is successfully growing on the vine (“Set on the vine”). You can be sure that fruit set has occurred several days after it was pollinated, when the baby fruit begins to noticeably grow on the vine.
If pollination does not occur successfully, or if anything goes wrong in the early stages of fruit growth, the plant will abort the fruit. The tiny fruit will shrivel, darken and perhaps turn black, and finally fall off the vine.
Inevitably this happens from time to time. When it does, do not panic. The season is long. More fruit will appear and be pollinated, ultimately leading to successful fruit set.
Also see these great resources:
How to pollinate pumpkins – pumpkin growers can hand pollinate female flowers, to increase the chances of successful pollination and fruit set.
Poor Pollination. – There are many reasons for poor pollination and failure of fruit to set on the vine. Find the causes and cures.
Plant Pollination – From the experts at The Gardener’s Network.