Animal welfare charities are urging people not to dump pumpkins outside and in open spaces once Halloween is over
The Woodland Trust, based in Grantham, says some people believe they will provide wildlife with food, or turn to compost and help trees.
However, the charity has warned pumpkins can be fatal to hedgehogs.
Paul Bunton, from the charity, said people should instead compost them at home, or hang them from a tree to feed the birds.
Every year, hundreds of pumpkins are dumped in woodlands across the UK, according to the charity.
“I think it is because people think they are doing something positive for the wildlife – giving them a bit of an autumn boost,” Mr Bunton said.
“But, actually they are doing the reverse – it can be very negative for wildlife,” he added.
The Woodland Trust has posted a video on its social media channels detailing the impact pumpkins can have on wildlife.
In it, Trevor Weeks, founder of the East Sussex Wildlife Rescue and Ambulance Service, says Halloween coincides with the time hedgehogs are looking to fatten themselves up for hibernation.
Pumpkins give them diarrhoea – they lose weight, dehydrate and “will struggle to survive hibernation”, he said.
The Woodland Trust has suggested pumpkins should instead be used as autumnal bird feeders, composted at home, or donated to zoos or farms for animal feed.