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Why Do Trees Grow in Spirals?

Posted by Rachel Wendling at Apr 04, 2017 03:30 PM |

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.


Spiral Pacific Yew, Circle Peak Trail. Photo by Kim Brown

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.

Fallen spiral snag
Relaxing spiral snag, Bernhardt Mine trail in the Pasayten Wilderness. Photo by Kim Brown

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.

Colorful spiral tree
Colorful spiral snag, Meeks Table in Gifford Pinchot National Forest. Photo by Jim Kuresman

This article originally appeared in the Mar+Apr 2017 issue of Washington Trails Magazine. Support trails as a member of WTA to get your one-year subscription to the magazine.

Comments

Rod Hooker on Why Do Trees Grow in Spirals?

In a March 2020 hike, two large Hemlock fir trees (snags) were like giant pillars on either side of the North Siouxan Creek Trail - Southwest Washington. One had a spiral grain pattern and one a normal linear pattern. Now, that’s curious. Same size and same ecozone and (presumably) same genetics, yet a response to something subtle to grow one way in one and normally in a brother. I was reminded of this article in the WTA magazine a few years ago on this subject and it spurred me to read more about the topic. The theories as to why this occurs somewhat irregularly and unpredictably, in my mind, are not very satisfying. Nor does it make for good lumber so fortunately, it is rare.

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Rod Hooker on Mar 21, 2020 01:49 PM