One of the oldest trees in Logan has been officially dated and named ahead of National Tree Day on Sunday.
The blue gum (Eucalyptus tereticornis) on a North Maclean property is estimated by an expert arborist to be 378 years old.
Its trunk is 2.38m thick and is estimated to be 34m high although the top has been snapped off, probably in a storm.
Landowner John Howes said he was surprised to learn the tree's age when tested under a program funded by Logan City Council.
"I'm just a boy compared to the age of this tree," said the 74-year-old retired blacksmith and boilermaker.
"We knew it was old just by looking at it but thought at best it might date back to around the time Captain Cook discovered Australia (1770)."
Testing by the arborist, which confirmed the tree dates to the 1640s, involved using an extremely thin drill probe which measures the resistance as it goes through the hard and soft wood of each year.
The data identifies a yearly growth pattern which enables the age of the tree to be estimated.
The arborist, Adam Tom, suggested giving the tree a name and chose Gandalf after the aged wizard in Lord of the Rings.
"We thought it was an appropriate name as the tree has a lot of character," Mr Howes said.
The tree is located on the bank of a picturesque upper reach of the Logan River.
Like many old eucalypts, Gandalf contains a number of hollows that provide shelter and habitat for native animals including possums, gliders, owls, parrots, ducks, rosellas, kingfishers, frogs and native bees.
"If the tree is still there when I go, that's where I wanted my ashes scattered," Mr Howes said.
This is the first year Council has undertaken a tree age testing program. It is hoped to expand the program with the help of other landowners and map historic old trees across the city.
City of Logan residents can help green the city and improve the environment by participating in a free community planting event to celebrate National Tree Day on Sunday (July 28).
Logan City Council will host the planting at Kingston's Eridani Park, in Eridani Avenue, from 8am to 10am.
The event is the biggest annual community planting in Logan with thousands of young trees and shrubs to be planted in the park.
Those wishing to participate are advised to bring drinking water, sun protection and wear enclosed shoes.
