Andrew Hunt, head gardener at Kingston Lacy, said pumpkins needed a long, hot growing season to do well.
He said only half of the estate’s normal crop was saved this year.
“Unfortunately, we had a cold and prolonged spring, which meant that germination took place later than normal and then the cooler and wetter conditions over the summer really haven’t helped,” he added.
Nostell, a Georgian house near Crofton, West Yorkshire, typically produces about 80 pumpkins and squash – but harvested just 25 this autumn.
Paul Dibb, the property’s garden and outdoors manager, said: “The wet spring and early summer has resulted in an army of slugs attacking the young plants we grew and planted out.
“It’s been a struggle to get any established in time to produce fruit.”