Asked August 26, 2016, 1:07 PM EDT
Washington County Oregon
Sorry to hear about the disappointing results to date. It’s difficult to provide an answer because too many details are missing, among them the pot size, what the pots are filled with (soil or potting mix?), the number of plants in each pot, water and fertilizer practices, hours of sunlight, and how the recent temperatures affected the activity levels of pollinator insects. In addition, images of the plants and their surroundings could provide additional details.
I suspect attempting to grow pumpkins in pots puts them at a disadvantage. “As a guideline for jack-o-lantern sizes (15-25 lbs), semi-vining varieties need 15-30 square feet per plant, full vining types 20-35 square feet per plant.” (https://agdev.anr.udel.edu/weeklycropupdate/?p=1583)
This webpage has some theories why male flowers might be missing, including inadequate nitrogen and phosphorus. It’s very likely both those are in short supply in pots unless fertilizer was added on a regular basis. http://pumpkinnook.com/howto/pumpkinflower.htm
“Growing squash in home gardens” may be useful: http://cru.cahe.wsu.edu/CEPublications/FS087E/FS087E.pdf