In the 1980’s, almost all of the Eastern Hemlocks in Westwoods died from the Woolley Adelgid disease, leaving what appear to be medieval weapons strewn about on the forest floor. These bludgeons are Hemlock branches with tapering concentric rings on the insertion end. When the branches are still attached to the mother bole, they remind me of sculptures.
Why do they taper like this? I asked my go-to tree person, David Zuckerman, who is a Horticulture Manager at the Washington Park Arboretum in Seattle and also my brother-in-law (read David’s blog about Hobbit Trees). This extra wood, called a collar, is laid down by the trunk to give the branches more support. David sent me a research paper by Alex Shigo, who is known in some circles as the “father of modern arboriculture.” Shigo’s diagrams indicate that Hemlock branches have thicker collars than most other species due to having a core of hard resin.