Watch: Christmas tree becomes raging inferno in alarming warning video

A US government agency has created a comparison video showing how quickly a dried out Christmas tree will burn up if ignited, compared with a well-watered one.

The video, created by the National Institute of Standards and Technology, put two identical trees side by side and sets them both alight at the same time.

The dry tree goes up very quickly, with flame engulfing the tree in under 10 seconds.

Meanwhile, at the end of the two-minute video, the fire inside the watered tree has gone out and tree is left intact.

National Risk Reduction Manager for Fire and Emergency New Zealand, Rob Saunders, told 1 NEWS about the number of call-outs they have for Christmas tree fires in NZ.

"The data we have available shows we have gone to 12 structure fires related to Christmas trees over the last six Christmas seasons, plus one so far this year.

"Anecdotally though we know the numbers of incidents we attend is higher."

He also has a warning for Kiwis over the disposal of the trees after the festive season.

"We urge people to be really careful with live Christmas trees and how they dispose of them this summer, especially with the dry weather."

A study conducted by Forest Products Laboratory in the US concluded that the best way to hydrate Christmas trees was to leave them standing in a container of plain water, and to regularly top it up.

A fully-hydrated tree will not catch alight, even when an open flame is held to the needles - but when the tree's moisture level drops below 85 per cent it can be easily ignited.

A house in Westport, New Zealand completely burned down in 2015 after the Christmas tree lights ignited the tree, with fire spreading to the ceiling.