To get a pumpkin to grow on the vine, you need two pumpkin flowers present and open, in your pumpkin patch at the same time. Not surprisingly, that would be a male flower, and a female flower. The males will arrive in your pumpkin patch first, and in big numbers. Then, 10-14 days (or so) later, a female will show up. Then, another female will bloom, and so on. The male flowers will usually far out-number the female flowers. That’s normal.
Learn about male and female flowers and see pumpkin flower pictures.
Normally, flowers begin to appear on a pumpkin vine several weeks after it has sprouted, and when the plant is several feet long. If you planted your pumpkin sometime in May, they will begin to bloom mid-June to early July. Once flowers begin to appear, a healthy plant produces flowers all the way up to frost. To get an orange pumpkin by September – October, you want your pumpkins to be growing on the vine by the mid to late August.
Once a male and a female arrive at the same time, Mother Nature can go about the business of pollination. See more on Pumpkin Pollination.
While awaiting the arrival of flowers and the first fruit, pumpkin growers get anxious. We wonder if something is wrong. Most often, it’s just our anxiety and impatience. After all, we haven’t seen a pumpkin since last year! Normally, our anxiety will be relieved in short order. In the meantime, we recommend a dose of Phosphorous fertilizer. This promotes blooming and fruit set. See more in the Role of Phosphorous. We also recommend that you cut back on Nitrogen fertilizers during the blooms stage, as this can delay blooming.
It is perfectly normal for the males to arrive first. And, they do so in big numbers. A week or so goes by without any ladies appearing, and you are beginning to think there’s a problem. The female flowers usually arrive 10-14 days after you spot the first male. (Sometimes it takes a little longer than this). Once the ladies appear, there will only be a few at a time. The male flowers greatly out-number the female flowers.
It is quite uncommon for female flowers to arrive first. On occasion this happens, and there are on pollen-laden male flowers. This situation should be short-lived, and the males will certainly arrive. More female and male flowers will continue to arrive all season long, offering plenty of opportunities for successful pollination. There are theories about why females occasionally arrive first. Some have to do with soil fertility levels. Others, suggest early season cold snaps may pre-dispose the plant to this condition. Check your soil fertility. Phosphorous levels should be good to high. Nitrogen levels should be slightly low to good, but not high.
If male flowers are lacking or sparse, there are two things you can do. First, pick ripe male flowers and put them in a glass with water in it. Place them in the refrigerator. Use them to hand pollinate, as necessary. They last in the refrigerator for up to a week. You can also ask a pumpkin growing friend for a few male flowers.
Almost always, a pumpkin grower that believes the flowers are not opening, has missed the event. Female flowers open for just one morning, sometimes closing up before noon. Cloudy and rainy weather can cause a flower not to open.