What’s causing 'exploding trees' in the Chicago area?

What’s causing 'exploding trees' in the Chicago area?

There’s a phenomenon sweeping social media that you may have seen — or even searched for — called “exploding trees."

CHICAGO - There’s a phenomenon sweeping social media that you may have seen — or even searched for — called "exploding trees."

What we know:

It’s reportedly caused by extreme and rapid drops in temperature. While it is a real occurrence, arborists say it’s not nearly as dramatic as it sounds.

The official term is "frost crack." It happens when moisture and sap inside a tree freeze during rapidly plunging temperatures. As the contents expand, pressure builds inside the trunk, causing it to split.

Certain trees are more susceptible than others, especially those with smooth bark. Sycamores are a common example.

If you look closely, you may even spot frost cracks in your own neighborhood.

What they're saying:

At the Chicago Botanic Garden, several sycamore trees have shown cracks for years. Tom Tiddens, supervisor of the Plant Health Care Department at the Chicago Botanic Garden, said the cracks can expand and contract as temperatures change.

"I expect by morning this frost crack will be opened up two-plus inches," Tiddens said. "If a tree has never experienced a frost crack before, the first time it happens, when it hits that certain point, the crack all of the sudden is like a split in your car windshield. It will kind of just kind of happen, and then that kind of fracture will be in the tree for the rest of its life. The first time it happens on a tree that hasn’t had it before, I’ve heard it sounds like a gun going off."

What you can do:

Tiddens said wrapping younger trees can sometimes help protect them during extreme cold, but it’s most effective when done in the fall.

If you have questions about tree care or frost cracks, the Lenhardt Library and Plant Information Service at the Chicago Botanic Garden can help.