Expert says Ardeth’s tree can be saved
Despite damage in wind storm, ‘Ardeth’s tree’ remains strong, expert says
There’s good news for Ottawa’s tree huggers, although soon they may not get close enough to hug the majestic Bebb’s oak known as “Ardeth’s tree.”
An international expert in tree hazard assessment says the oak, which was severely damaged in a storm last week, has decades of life left.
“I know this tree will survive,” said Mississauga-based Philip van Wassenaer, who lectures around the world on conserving old and ancient trees. “This (the damage) is not fantastic for the tree, but it’s just a stage of life for this tree.”
The massive oak, on the east side of Prince of Wales Drive in the Dominion Arboretum, is known for its horizontal branches, which make it perfect for climbing. The trunk bears a plaque to commemorate Ardeth Wood, the 27-yearold graduate student whose disappearance in 2003 galvanized hundreds of volunteers to help in the search for her. Wood was found slain five days later.
On Sept. 27, violent storm winds sheared away about a third of the oak’s trunk, taking two large branches with it and raising questions about whether the tree could survive. In recent days, Ottawaarea experts consulted by Agriculture and Agri-Food Canada have all concluded the oak is still sound.
On Tuesday, van Wassenaer climbed the tree, took measurements and performed a number of tests, including checking its density using tomography, the same imaging technology used to detect tumours in humans.
“In Great Britain, there are thousands of old and ancient trees. They say a tree will grow for 300 years, rest for 300 years and it will expire gracefully. This tree will have a long life in front of it,” he said.
A Bebb’s oak is a natural hybrid of white oak and bur oak. According to van Wassenaer’s measurements, the tree is 21 metres (about 70 feet) tall, has a girth of 5.75 metres (almost 19 feet) and a diameter of 1.735 metres (about five-and-ahalf feet). Despite the apparent antiquity of the tree, it is actually only about 120 years old. Van Wassenaer first saw the Bebb’s oak in June when he was in Ottawa for a conference. He heard about the damage from a colleague in New Zealand, who sent him a photo of the harm inflected by the storm.
This tree has a “co-dominant stem,” which means it has stems of about the same size emerging from the trunk. It’s a structural weakness in any tree, although many trees with a co-dominant stem never fail. The problem here was a sudden burst of wind. Strong winds “determine where the weaknesses are,” said van Wassenaer. However, the surviving side remains very strong, and there is little evidence of decay.
Trees in an arboretum grow differently from those in a forest, van Wassenaer said. In a forest, trees grow tall to form a canopy in a competition to access sunlight. In an arboretum, branches spread outward in an attempt to access light from the sides.
If a branch is no longer able to perform this role, the tree will shut it down and the branch will eventually die.
“We can describe trees as longlived shedding organisms,” van Wassenaer said. “What happened here is a survival response.”
The damage will still be a shock to the tree’s system. Other branches on the tree have similar characteristics, so it will be necessary to take precautions, he said. One surviving branch already has a brace, and it may be necessary to add others, as well as a fence around the tree to keep people away. It also appears the oak’s days as a magnet for tree climbers are over.
The tree will try to grow bark to cover the damage, but the injury is too large for that to happen. Over time, the colour of the wood will change. In 40 or 50 years, decay might set in, but that’s unlikely as long as the wood is dry, van Wassenaer said.
The news is a relief to JeanPascal Gratton, supervisor of the Dominion Arboretum. He still has to present the findings of all the experts to senior managers at Agriculture Canada, who will make a final decision on the tree’s future.
“We will do everything in our power to help this tree,” Gratton said.
Mike Rosen, president of Tree Canada, was present Tuesday while van Wassenaer completed his assessment. He got to know the oak more than 30 years ago when he was a student treating elms for Dutch elm disease.
Trees have environmental, economic and social benefits, Rosen said. In the case of this tree, it’s the social element that is significant.
Research has shown that people feel better around trees and the effects are exponentially more significant around large trees.
“People want to be awed by this tree,” Rosen said.