200-year-old tree explodes because of Oregon heat wave, expert says

PORTLAND, Ore. (KPTV/Gray News) - During the seven-day heat wave in Portland, a huge branch of an oak tree broke and fell in the Eastmoreland neighborhood, taking down power lines with it. It looks like the heat may have caused the tree to explode.

The tree, estimated to be more than 200 years old, looked perfectly healthy, but seven days of temperatures at 95 degrees or above may have been the cause of the branch falling. The branch was estimated to weigh roughly 30,000 pounds.

No one was hurt and the property damage was minimal. But it was a healthy and regularly maintained tree.

The old oak had just gone through the longest heat wave on record in the Portland area.

That kind of heat is not healthy for people, but it’s also not healthy for even the oldest and most resilient trees.

Arborist Michael Jolliff told KPTV how intense heat can cause a tree to explode.

“That [heat] tends to cause thermal changes inside the tree in the wood tissues and also the buildup of gases inside the tree,” he said. “That can be explosive and sudden.”

Jolliff said these explosions happen in the big old trees, especially oaks, the kind loved for the shade they bring in the summer’s heat. He said the weight of these trees is also a factor.

“We have seen it in a sense explode because, under that amount of weight, you hear it. It’s very dynamic,” he said.

The aftermath looks like an explosion, too, as the tree spontaneously pulled itself apart.

In Powell Park last week, another huge branch came down. Jolliff said there was some rot there, but he also thinks heat and the massive tree’s weight played a part.

A warming climate could mean people will see more explosions in trees, he said.

“We’re going to continue to see it because of the way the heat is trending,” said Jolliff. “There isn’t any real precursor or warnings, and that’s the problem. No tree is perfectly safe.”

Jolliff said sometimes they can brace a tree’s possible failure points, but that is not foolproof.

The heritage tree survived more than 200 years and a slew of ice storms. But Portland’s heat may have been too much for one of Eastmoreland’s favorite old oaks.

The tree will have to be completely removed.