Derek Halford shows off his Doryathes Palmeri flower, which has taken 20 years to bloom and may not bloom again for another 20 years.

It's been 20 years in the making but a giant and rare lily has chosen 2016 as the year to produce its first-ever flower.

Grown by Derek Halford in Rangiotu, the giant spear lily - a Doryathes Palmeri - is considered endangered in its native Australia and there are only about five of the plants in New Zealand.

Halford runs a tree peony garden on his 40-hectare property and was given the lily from a property in Whanganui.

David Unwin/Fairfax NZ. Derek Halford's Doryathes Palmeri flower, which has taken 20 years to bloom and won't bloom again for another 20 years.

"It's supposed to flower every 13 years. I had it out in the gardens and I got sick of waiting for it, so I shifted it. Last year I was doing a bit of fencing and 'hello' I saw this spike starting to grow. It's now five metres tall."

The flowering spear will eventually die and Halford said he will probably have to wait another 20 years to see it again.

"I'm 74 now, so who knows if I'll get to see it again in my lifetime."

The plant is endemic to north-east New South Wales and south-east Queensland and Halford said there were only 100 sites in Australia where it was growing.

"The aborigines used to pulverise the spikes to make a thing to chew out of it.

"The spike will die and then it will grow pups around the base and then you can take those off. To make the pups grow in a hurry you build a fire around them and let it burn. It's the heat and the smoke that helps them germinate."

Halford already has a list of people who want one of the pups and he will also collect the seeds. Halford said at the moment the birds were enjoying the nectar.

"The birds pollinate it and we've had hoards of tui around. The birds love it."