In certain types of trees such as – but not limited to – eucalyptus, Sitka spruce, and Japanese larch, a unique phenomenon where the uppermost branches of trees don’t touch can be observed. It’s called “crown shyness”, where the crowns of trees are separated by a gap clearly visible when viewed from the ground level.
Even though it first appeared in scientific literature in the 1920s, a consensus has not yet been reached regarding its real cause. Most of the time, it is manifested by trees of the same species, but there have also been accounts of it occurring among those of a different species.
While there is no united answer from researchers regarding why this unique behavior happens, numerous scientists have presented their own theories.
Australian forester M.R. Jacobs wrote in his 1955 book, “Growth Habits of the Eucalypts”, that the growing tips of trees are sensitive to abrasion, therefore causing the gaps between the branches. In 1986, this theory was backed by Dr. Miguel Franco, who observed that the branches of Picea sitchensis (Sitka spruce) and Larix kaempferi trees were damaged from abrasion, which caused the complete destruction of the branches.
Some experiments have also proven that when trees exhibiting crown shyness were artificially prevented from touching each other, they eventually fill in the gaps between them.
The above theories definitely seem valid, but the most prominent of them all says that crown shyness is a form of defense mechanism by trees to prevent invasive insects from thriving. These pests have the ability to build structures that can go as long as 10 centimeters off of tree branches in order to reach other plants. The gaps between are the trees’ way of stopping these bugs.
One Malaysian scholar, however, had a different stance. He studied the Dryobalanops aromatica trees and found no signs of abrasion despite their apparent crown shyness. He believes that the uppermost branches of the trees were sensitive to light levels and that their growth halts when they get too close to other trees.
But while the real cause of crown shyness is still shrouded in mystery, it can’t be denied that it is a picture perfect phenomenon. Just look at all these gorgeous patterns created by those gaps!
Have you ever been to a forest where trees exhibited crown shyness? Let us know in the comments and share those beautiful pictures!