Trees sleep

Researchers pointed laser scanners at birch trees and scanned them all night long.

After sunset the branches started to sag. They kept sagging for hours, bottoming out about two hours before sunrise—as much as 10 centimetres on a tree only five metres tall—and then slowly lifted back to where they had been.

Nobody told the trees when sunrise was coming. They lifted anyway.

What does your body do at night that you never notice?

Sources

• Quantification of Overnight Movement of Birch Branches and Foliage with Short Interval Terrestrial Laser Scanning — 2016

Sources checked 2026-08-12.