You don’t want to be in front of the Chinese witch hazel when its fruit bursts open. The plant—long known for its anti-inflammatory properties—can fire seeds at more than 12 meters per second, and with the force of a bullet fired from a 19th century gun. Now, for the first time, researchers have revealed how the remarkable behavior works.
Chinese witch hazel (Hamamelis mollis) grows a hard, fuzzy fruit that ripens about a year after the plant is pollinated. Using MRI scans, researchers discovered that when the plant is ready to release its seeds, the outer layer of the fruit shrinks, while the fleshy inner portion both shrinks and expands. This constricts the middle section of the fruit, forcing the seeds to pop out with an audible crack, the team reports today in the Journal of the Royal Society Interface.
The seeds feature a ridge that pushes against the inner fruit chamber as they’re fired, causing them to spin nearly 26,000 times per minute. The spin stabilizes the seeds as they become projectiles, much like bullets in rifles.
In ideal conditions, the plant can send seeds up to 18 meters away, the researchers calculate. That’s about the length of a bowling lane and three times the largest recorded distance traveled by seeds in the witch hazel family.
The Chinese witch hazel may have evolved this spectacular shooting style because it’s tucked away beneath the canopy of taller plants and trees in forests. Firing seeds out so far may have allowed it to spread to new environments faster and avoid overcrowded areas.