The pollination period of a pumpkin’s life cycle is an anxious time. A lot of things can go wrong. However, successful pumpkin fruit set eliminates those concerns and is a 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. And, it is growing in a healthy manner. Specifically, proper fruit set is confirmed by observing the growth of the baby pumpkin.
However, 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”). Literally, it is the transition from a female flower into a young, vibrant fruit. We confirm that proper fruit set several days after pollination, 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. It happens for a variety of reasons. When it does, do not panic. The season is long. Without a doubt, more fruit will appear, and then successful pollination occurs. Ultimately, it leads to successful fruit set.
There are several reasons why pumpkins are not setting fruit. To correct this and have a successful gardening season, you first need to identify the cause. Then, you need to implement the cure. Here are the issues:
Cause: Too much nitrogen in the soil results in lots of healthy green foliage. However, flower production is delayed, minimized, or doesn’t occur at all.
Cure: Stop applying high nitrogen fertilizer during, and just prior to, the pollination period. Also, apply a high- phosphorous fertilizer to promote flower production.
Cause: There are several reasons for poor pollination. And, poor pollination is the number one cause for pumpkin fruit set failure.
Cure: Poor pollination is such a large topic, that we have devoted a whole article to it. See: Poor Pollination FAQs.
Cause: High temperatures cause stress on pumpkin plants. As a result, the plant produces more male flowers, and fewer females. Pumpkin pollination and fruit set usually occurs. But, it does so at a lower number of fruit.
Cure: Poor on the water during periods of drought. Remember, the plant grows best in evenly moist, but not wet soil.
Cause: High temperatures are another serious plant stressor. As a result, the plant will often drop flowers or abort the tiny baby fruit.
Cure: There’s not a ot you can do about high temperature conditions. However, providing adequate water helps. And, you may consider installing a partial shade over.
Cause: While pumpkin plants require lots of water, the goal is evenly moist soil during the entire growing cycle. Too much water and soggy soil can cause root rot and other plant problems. This stress in turn causes the plant to produce fewer male and female flowers. And, those that pollinate may fail to result in pumpkins not setting fruit.
Cure: Plant pumpkins in well-draining soil. Allow adequate drainage during periods of heavy rain. And, do not overwater the plants.
Also see these great resources:
How to pollinate pumpkins – Pumpkin growers can hand-pollinate female flowers. It increases the chances of successful pollination and fruit set.
Poor Pollination – There are many reasons for poor pollination and the failure of fruit to set on the vine. Find the causes and cures.
Plant Pollination – From the experts at The Gardener’s Network.
