"They are the biggest I have ever had and I have been growing them on and off for years."
His wife Patricia was also dumbfounded and wondered if the weather played its part in the huge haul.
"We have eaten quite a few and given away quite a few. I think it's something to do with this season - the feijoas, everything's big."
Mr Flanders believes it's imperative to start with good stock - a keen gardner around the corner provided some "fine" specimens, which he planted in the traditional way, each one set atop a mound.
The idea is to have firmer soil below - his was a little soft but the red kumara didn't seem to mind. There was no growth boosting formula or preferential treatment - just some water and a watchful eye - yet for some reason they thrived.
"You just have to make sure the runners don't root again, I lift them up about once a month - they are easier to grow than potatoes."
One of the biggest weighed in at more than 3kg and had been quite a talking point among friends and family, including the woman who gave Mr Flanders the plants.
"I took some round there and she lit up like diamonds, she said she's had some big ones before - but not quite this big."
His youngest grandson Cooper is more likely to be seen ploughing down the rugby field, than a vege patch but was more than happy to pose with his ball and the largest of his poppa's crop.
There was speculation as to whether they would taste as good as they look, but it turns out the larger root vegetables are just as sweet.
What exactly does one do with a behemoth kumara?: "chips, a big pot of chips - they make good soup too."
It wasn't just a bumper season for kumara - his tomatoes too were particularly large and lettuces were epic.
