“I’d like some info on why my pumpkin seeds didn’t produce pumpkins. There were lots of leaves and flowers, but no pumpkins. I planted them plenty early enough, and there wasn’t any frost. The leaves just started dying out by mid-September.” Question from Kimberly of Vancouver, Washington
Answer: Sorry to hear your pumpkin vines did not produce pumpkins! First, make sure that all of their growing requirements are met. Pumpkins need to be planted in spring, after the threat of frost has passed, for fall harvest. Full sun, summer warmth, and space (a 12’ x 12′ to 15 x 15’ patch) are essential for vining varieties. It pays to plant them on berms (click here to read all about berming) amended with lots of organic matter. Feed them with a fertilizer formulated for vegetables, and be sure they get plenty of moisture (probably not a problem in Vancouver).
If all their growing requirements were met, there are four more possible reasons why your pumpkins did not develop.
1. Lack of pollinators
Pumpkins have two flower types, male and female, and these are bee-pollinated. The male flowers are produced first, followed by the female blooms, which have small, underdeveloped pumpkins at the base of each flower. If you see female blooms on your plants, and no bees, this could be the problem. Without pollination, the developing fruits just shrivel and drop. If you think this is the cause of your troubles, try a hand-pollination method. Simply use a small brush to move pollen from a newly opened male flower to a newly opened female flower. It’s fast, easy, and will yield pumpkins!
Lots of pumpkin varieties require good growing conditions for more than 100 days to produce. Early pumpkins are a good choice for those living further north. The varieties ‘Flatso‘ (85 days to harvest), ‘Chucky‘ (85 days to harvest), and ‘Cinnamon Girl‘ (85 days to harvest) are all early to produce.
Some fungal diseases and disorders will cause the fruit to shrivel up at various stages of development if you don’t think pollinators are your problem. (Click here to read a great article from Purdue University about pumpkin diseases and solutions.)
4. Squash Vine Borers
These pests bore into the stems of pumpkins and other squash and cause whole vines to die back because they are cut off their water. Usually, with vining pumpkins, some of the vines survive because they root along the ground and survive, so this is often less of a problem. Nonetheless, click here to read a great Q&A about squash vine borers to determine if this is your problem.
Better luck with your pumpkins next year!
Black Gold Horticulturist