Scientists Film Blue Glow on Trees During Thunderstorms

Scientists just proved that trees literally glow during thunderstorms, and it happens everywhere.

For nearly 100 years, researchers suspected that weak electrical discharges called coronae formed on leaf tips during storms, but nobody had ever seen them in nature until now. A team led by meteorologist Patrick McFarland from Penn State finally caught these elusive blue sparkles on camera during summer 2024, watching them dance across branches up and down the East Coast.

The glows are too faint for human eyes to see under stormy skies, but they're definitely there. McFarland's team observed 41 separate coronae on a single sweetgum tree in just 90 minutes, with each glow lasting up to 3 seconds and sometimes hopping from leaf to leaf like tiny lightning bugs.

Here's how it works: The electrical charge from a thunderstorm overhead creates an opposite charge in the ground below. That ground charge climbs up through tree trunks to reach the highest points it can find, the tips of leaves and needles, where it releases as a subtle blue glow.

To catch these ghostly lights, the team transformed a 2013 Toyota Sienna into a storm-chasing laboratory. They cut a twelve-inch hole in the roof, mounted a periscope connected to an ultraviolet camera, and added weather stations and electric field detectors. McFarland jokes that they totally killed the minivan's resale value, but science was worth it.

The team hunched around a video feed during raging thunderstorms, straining to spot the faintest signals. "You're looking for the faintest signals on a video feed of nothing," McFarland explained. Only later, analyzing the footage, did they confirm what they'd captured.

Lab experiments revealed something fascinating about these coronae. They actually burn the very tips of leaves and break down cell membranes that trees use for photosynthesis. Since this likely happens across entire forest canopies during storms, McFarland speculates that trees may have evolved specific features to limit this damage over millions of years.

Why This Inspires

This discovery transforms how we understand the relationship between trees and weather. Every thunderstorm that rolls through a forest creates an invisible light show across millions of leaves, a natural phenomenon that's been happening since trees first evolved but remained hidden from human observation until now.

The finding also opens new doors for research. The team discovered that coronae's ultraviolet radiation scales directly with electrical current in trees, potentially giving scientists a new tool to measure how storms affect forests and how trees protect themselves.

Sometimes the most magical discoveries aren't about finding something new, but finally seeing what's been there all along.