end about the tree failure question! Many of you zoned in on an important point visible in the two photos I shared. The tree’s base was obviously quite narrow where the trunk broke, and with the tree’s vase-like architecture this led to breakage. But why was the base so narrow?
Again, several of you thought about root issues, such as a restricted root zone, or possible damage to the lower trunk. Actually, it’s a combination of root and trunk issues, as this last photo shows:
What we have is a large circling root (you can see it at the soil surface to the left and right of the trunk) that has girdled the trunk completely and prevented it from growing in diameter. The trunk above this point continued to grow, eventually creating the instability that eventually led to failure.
This tree used to be the focal point of a small urban landscape. It was planted about 15-20 years prior to failure and obviously had poor roots. It irks me that the industry cannot figure out a way to (a) produce trees with decent roots and (b) plant them correctly. No wonder so many ISA-certified arborists are now recommending that people only purchase bare-root trees, so that these heart-breaking scenarios are avoided.
Congratulations to Jimbo in Australia for being the first to identify this particular problem, and honorable mentions to those of you who had logical and realistic diagnoses for tree failure.
(I hate to take pleasure out of the fact that girdling roots are a significant source of tree failure in Australia, but Jeff and Bert give me so much grief about root washing that I was starting to wonder if it was only the Pacific NW that was cursed with this problem. Guess not!)