The largest at the Sydney Royal Easter Show this year was 230 kilograms, grown by the team in the southern districts division.

Large pumpkin-growing is an involved process, and many growers treat their pumpkins "like babies" in the lead-up to a competition.

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And they aren't just any regular pumpkins, either - people harvest seeds from award-wining pumpkins in the hopes they'll have another biggun on their hands.

Barry Unger, pavilion steward at the upcoming Dubbo Show, has grown many big pumpkins, for both the local Dubbo Show and the Sydney Royal.

He said pumpkin vines were "a bit like humans" - they required feeding, shelter and water, and they also had "hormone stages" a bit like ours.

"In humans, you have conception, birth, infants, adolescence, normal growth and reproduction. In pumpkins, [there is] germination, growth, adolescence, full growth stage, then reproductive stage," Mr Unger told the Daily Liberal.

You wouldn't want to eat the big pumpkins they enter in agricultural shows. They are a type of 'stock pumpkin' or a 'gourd' - a mix between a stock pumpkin and another variety, favoured for their ability to grow very large.

"They're a cattle pumpkin - not an edible one," Mr Unger said.

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"Cattle pumpkins probably came from Europe years ago and they've been crossed with something else - a pacific breed for large pumpkins.

"They used to feed the flesh to cattle when they were locked up in winter, in Europe."

Mr Unger has left the big pumpkin-growing game and he works selling liquid fertiliser - but he is keen to get back into growing large pumpkins this spring.

He said the trick was good soil and feeding the plant well. Growers were well-advised to pinch off subsequent growing points so they had only one pumpkin per vine, into which the plant could put all its energy. Some growers turned the water off to 'stress' the plant which could make it grow a bigger pumpkin.

"You also need a good supply of bees because they're open-pollinated," Mr Unger said.

Pumpkins could be sunburnt so growers needed to give them shade, and elevate them up off the ground so they didn't rot underneath - wood then carpet was a good option.

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The weather could also play a role in pumpkin-growing.

"[Seeds are sown around] spring, September onwards, and harvest is around January - depending on the growing season, whether it's hot, or how rapidly they grow and how you feed them," Mr Unger said.

The largest pumpkin Mr Unger has grown is 35 kilograms, a lot of which is water weight. Serious big pumpkin-growers keep the seeds to themselves, because they are "like gold".

"They'll become like babies, they'll watch them and monitor them. A lot of it is genetic - you'll get the seeds out of that big pumpkin and whether the genetics are right," he said.

"It's good fun. It's like winning the best cow, isn't it?"

Disaster struck years ago when he was growing a show entry pumpkin, only for a rodent to pay an unwanted visit.

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"I had one I was growing a couple years back for Dubbo show. I thought, that's the pumpkin that's going to the show. A bloody mouse came in and ate all the gizzards, he ate all the seeds, he cleaned it from inside out," Mr Unger said.

Mr Unger will be stewarding the grain section at this year's Dubbo Show. He also organises grain for the western districts division at the Sydney Royal: "I do farm produce, grain, sorghum, hay."

The Dubbo Show celebrates 150 years in 2023, and will take place from Friday, May 19 until Sunday, May 21. Find out more at www.dubboshow.org/annual-show