This year's entry took three months to grow. When it was weighed in Marton he was rapt - it had been estimated at 450kg.
His mum, Jant Akkerman, has a large vegetable garden which the family helps out with. His dad Steffen has helped with rigging some of the watering.
To grow such large pumpkins you need a lot of water.
"I grew a few rock melons, but in the end the water went on the pumpkins" said Aaron.
"I've got a soaker feed throughout the patch. Dad put up a big arc sprinkler in the middle of the patch, which is turned on now and again to get them watered evenly. They need about 70 litres of water every couple of days to keep the soil moisture level consistent. It's the balance that matters, too much water and they will split."
The pumpkin's not really good for eating, given the fungicide used. Aaron only used a bit this year after a stem split early in the growing season.
He uses heaps of manure, mainly from sheep from a neighbour's shearing shed, and cow manure.
"I also use seaweed and an old bottle of Bio-Gold I found in the shed. I also add TM Best, which farmers put on paddocks. It really works. I've ordered a whole pile more.
"I also use Agrisol and an American product, Lithovit, which you put on leaves to enhance the chlorophyll."
Another trick is an extension to the watering can which means Aaron can water with his sheep manure-infused concoction - which he brews in a big barrel - without compacting the soil and damaging the plant's roots.
He's aiming for the New Zealand record, which is 721kg. The biggest pumpkin-growing competition in the country is in Hamilton at the Pumpkin Harvest Festival later in the year.
Aaron won't be going.
"It's a long way to haul a pumpkin."
He may just blow it up instead.
"I blew up my 200kg one. It went sky high." He won't explain how. "Top secret."