Farmer Mark Baggs has spent countless hours nurturing the giant squash after planting it in a 500ft polytunnel six months ago.
He estimates it currently weighs 1,500lbs, the same as a Smart Car, but he hopes it will break the UK record of 1,504lbs - or 107 stone.
It is so heavy it has to be lifted onto a trailer using a forklift truck.
But there is some way to go until Mr Baggs, from Wareham, Dorset, smashes the world record - a pumpkin grown in the US last year weighed in at 2,009lbs.
In 2007 Mr Baggs grew the world’s biggest marrow, which weighed in at 9st 10lbs.
The 30-year-old said: 'I think the pumpkin has done so well because it’s been grown from a good genetic seed.
'It’s been a nice summer after a very cold spring. The real test will be seeing how dense it is and whether there are any holes in the bottom which could ruin my chances.
'I won’t know exactly how much it weighs until I get it on the scales but I have a weight estimation table that indicates it’s around 1,500lbs.
'I’ve been growing these things since 2005 and you really have to know what you’re doing.
'They only grow for one season, so you only get one shot at the record each year.'
Pumpkins belong to the squash family and are thought to have originated in North America between 7,000 and 5500 BC.