Mr Winterburn said the fruit trees grew naturally with no special care or attention, no addition of any secret formula or genetic modifying.
"I've never seen one this big before," he said. "It looks more like a big avocado than a feijoa."
He said they had heard of a big feijoa harvested in Hawke's Bay, but the Gonville one weighed in heavier by about 50g.
The feijoa, Acca sellowiana, is a flowering plant in the myrtle family and is native to much of South America but now grows globally.
While the Gonville giant might be the biggest grown this season, it's a lightweight compared to the 385g one grown by a Havelock North orchardist last year.