Trees Are Aware of Their Neighbors and Give Them Room

In "crown shyness," some tree species respect those nearby and keep their leaves to themselves.

Sky through a conopy of trees

Dag Peak / Flickr

I could write about trees until I was green in the gills, and I do. And it's probable that every time I write about them, I slip into anthropomorphizing them. Maybe they don't walk around and fly to the moon, but they are truly remarkable organisms with gifts and talents all their own. They are some of the planet's most noble workhorses – we'd be nothing without them – and they deserve all the respect they can get.

So is it any wonder that my heart skipped a beat when I read Robert Macfarlane's ‏word(s) of the day on Twitter? (Macfarlane writes about nature and language, and his Twitter feed is a profound and poetic thing.)

And many are the photos that flaunt this beautiful behavior.

Crown shyness
 Mikenorton / Wikimedia Commons / CC BY 2.0

The phenomenon has been studied since the 1920s and is also known as canopy disengagement, canopy shyness, or intercrown spacing. It doesn't happen in all tree species; some species that do it only do it with trees from the same species – some species do it with their own as well as other species. There is not one proven theory behind the reticence; it's believed that there actually may be several mechanisms across different species for this adaptive behavior. A case of convergent evolution.

tree shyness
 Patrice75800 / Wikimedia Commons / CC BY 2.0

One explanation is that it is a matter of self-pruning, of sorts; as trees rub against each other in the wind, they become stand-offish in order to stop the abrasion. Another theory suggests that it has to do with light and shade avoidance responses. One study showed plants arranged their leaves differently when growing amongst kin or unrelated specimens, shading neighbors of different species, but allowing important light to reach their kin. Finally, it could quite possibly be a way to protect neighbors from traveling pests.

Whatever the reason, there is obviously some smarts at play. And the ensuing result for us admirers – rivulets of sky peeking down like a ceiling map of rivers – provides the perfect excuse to ponder our clever arboreal allies and remember this: They may not be concerned with keeping up with the Joneses, but they're clearly aware of their neighbors.