Why Do Trees Grow in Spirals?
Washington is full of beauty— summits, mountain lakes, shrubsteppe, the Salish Sea, the Pacific Ocean and forests—that beckons us outdoors. Along with this pronounced beauty comes a plethora of natural oddities.
By Kim Brown
Washington is full of beauty— summits, mountain lakes, shrubsteppe, the Salish Sea, the Pacific Ocean and forests—that beckons us outdoors. Along with this pronounced beauty comes a plethora of natural oddities. I found one such oddity when I tripped over it. Once I was on the ground, I noticed that the log that had tripped me up had a beautiful corkscrew pattern.
I wanted to know why. I contacted Kevin James, ecologist and botany program manager with the Mt. Baker-Snoqualmie National Forest. James was happy to share a peer-reviewed article about spiral grain in trees. Though dated, this article is cited in many newer publications and websites.
Here’s what I learned:
This spiral pattern is a clever adaptation for survival. Because the bark and wood of trees do not grow together, the spiral pattern is not usually evident until bark drops off the tree.
The wood cells in trees growing in a windy area or on an unusually uneven substrate—such as shore pines that grow in both windy and sandy areas—can begin to grow in a spiral pattern to give the tree and branches more strength. A spiral pattern can also develop to strengthen tree trunks tasked with supporting an unusually heavy or uneven canopy.
A spiral grain also efficiently delivers sap and food throughout the tree when a straight grain isn’t sufficient. In a model tree (straight grain, living in ideal conditions), sap and food travel up and down a tree as if on a highway, delivering sustenance to branches and roots located in their straight line of travel.
However, conditions rarely match the ideal, and so the tree must adapt. Perhaps a root is located in poorly drained soil. The tree’s wood cells then form a spiral pattern that allows sap and food to be distributed to all roots and branches of the tree.
Next time you see a spiral-grained snag, think about why it grew that way. Was it challenging conditions, the necessity for more strength, or both? Either way, you will know that spiral grain is not a tortuous freak of nature. Rather, it is a wonderful adaptation.