New Plymouth's Peter Dove got a bloomin' surprise to find the cactus he had been nurturing for more than a decade had suddenly grown flowers bigger than saucers.

"They're the biggest flowers I've ever seen on a cactus," the green-thumbed succulent buff said.

"And I've got a lot of cactuses."

CHARLOTTE CURD/Fairfax NZ Peter Dove's huge flowering cactus has been 12 years in the making.

Measuring about two metres in height and believed to be from the Cereus or the Trichocereus family, the plant has been the pride of Dove's extensive and varied cacti collection for 12 years.

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He originally had the pencil straight cactus growing in his conservatory but as it began to tower in height the Moturoa resident had to move it outside.

"It's probably grown through the bottom of the pot and into the ground by now," he reckoned.

"It's been through a lot - after I moved it, it was blown over and it snapped."

Dove quickly tended to the spiky plant, tying it to the fence where he left it to mend and continued to monitor its growth.

While many of his other cacti randomly bloomed flowers of strange, yet beautiful descriptions, it was the first time this plant had developed a flower, let alone two.

Dove didn't believe it could happen and was taken aback when he was greeted with the exotic looking blossoms, which measured about 15 centimetres in width, at the weekend.

"I was pretty stoked when I saw them, it's pretty rare," Dove, who only has a small garden but packs it out with edible greenery such as lemongrass, tomatoes, taro and pumpkins, said.

"They won't last long though."

Longtime collector of cacti, New Plymouth man Neil Foster believed Dove's cactus was from the Cereus or the Trichocereus family, both native to South America.

Of those two families he said there were many similar looking cacti and it was often hard to distinguish between the breeds.

The flowers were also very similar in appearance and some were scented while others were not.

Foster said the blooms on the Cereus or the Trichocereus cacti would usually develop once a year and they generally lasted for about two days before they dropped off and died.

The flowers would begin to grow once the plant began to mature, which depended on whether the cactus was grown from seed or a cutting, which sped up the cycle.

The stem's break in earlier years may have been why Dove's cactus had not produced any flowers until now, Foster said.

"That would have knocked it back a bit."