Sorrell gardener Shane Newitt broke his own title with a 731 kilogram whopper.

Mr Newitt named the pumpkin CJ, after his friend, Cliff John McKnight, who recently died of lung cancer.

"He'd be chuffed and proud," Mr Newitt said.

"He had the faith that I had all the skill in the world and education to grow an Australian record, possibly a world record.

"That's why I decided to grow it in honour of him... and put my best foot forward and grow a great big figure and grow the Australian record, and I've come in very close."

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The pumpkin, which was entered into the D W Kingston Memorial Challenge at the Bream Creek show, was the second heaviest ever grown in any state, with NSW holding the title.

Launceston Horticultural Society show manager Noel Button said it was an amazing effort, especially given growing conditions were less favourable than in NSW.

"Shane has got a real passion... it's an amazing accomplishment," he said.

"He's very scientific, he spends a lot of time researching, he communicates with all these growers all over the world... it's amazing what he does."