Yellow Castlecliff pohutukawa has its origins on Motiti Island

This large tree is in full flower. Photograph by Bevan Conley.

A tree in full yellow flower has caught the eye of Whanganui man Arthur Harris.

It's on the corner of Tainui and Cornfoot sts, near the entrance to Castlecliff Golf Course.

"I've been noticing it for years, and I was surprised to find out it was a pohutukawa," he said.

It is, and pohutukawa can flower in a lot of different shades, Whanganui plant ecologist Colin Ogle said.

"Some are much more crimson, some are more scarlet and some are almost pinkish."

Yellow-flowered pohutukawa are reasonably common. He remembers a line of them in Hawera and said others have been planted on a coastal Whanganui farm.

They may have all arisen from two chance trees, discovered on Motiti Island in the Bay of Plenty. Since then the yellow-flowered strain has been propagated and sold.

It tends to flower earlier than red-flowered pohutukawa. All pohutukawa flower a bit intermittently - and not always prolifically.

"There are good years and poorer years. I've never seen a year when pohutukawa didn't flower," Mr Ogle said.

There are two main pohutukawa species in Whanganui - the usual one and a species from the Kermadec Islands. The two tend to interbreed, and both are at risk from myrtle rust.