Britons looking to add some fear factor to their homes this Halloween with large pumpkins could be left disappointed after the Royal Horticultural Society warned that pumpkins are likely to be smaller than normal this year.

Experts at the RHS say that an unusually dry spring and a cool, damp weather conditions in late summer have prevented pumpkins from developing properly.

UK gardeners growing the fruit have also been affected by thriving mildew, while a lack of high temperatures for long periods of sunshine through the summer has stopped the plants from growing well.

Leigh Hunt, principal horticultural adviser for the RHS, said: “It’s been a strange year. To start with, a dry start to the summer meant plants struggled to get roots into the ground and establish properly.”

“By August, we were getting cooler temperatures into the night, and it slows down the plant and the way the fruit develops.”

“People were finding the flowers rotting off; other people were finding the fruits were coming but it was very slow, and where it got really soggy, they were getting some of the fruits rotting off.”

He said that in the south-west and south-east regions of England growers struggled in the face of damp conditions, while in the Midlands, people had experienced dry but not sunny weather.

However, Mr Hunt insisted the news was not all bad for people wanting to carve Halloween pumpkins, as smaller fruit would be more suitable for children to have a go at turning into lanterns. And with orchards turning in a bumper year, he also said there will be plenty of English fruit for the traditional game of apple bobbing .