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Branch unions dissected

branch unions dissectedUnions on branches that remain small compared to the trunk develop overlapping wood collars (collars do not form on codominant stems). The result is a strong connection between the branch and the trunk. The photo on the right shows a union where trunk wood was entirely decayed away. The ridges of wood are the annual branch collars that formed around last year's trunk wood. There are about 11 collars clearly visible with several older collars decayed away and missing. I often use the analagy of a lag screw inserted into a piece of wood to illustrate branch connections. In this analagy the branch is the lag, the collars are the threads of the lag, and the trunk is the piece of wood. Just as it is difficult to pull a lag out of a piece of wood without unscrewing it, it is difficult to pull a branch from a trunk that is small compared to the trunk. Note that there are no collars present in the union below; that is the reason it pulled out of the trunk. Unions with bark inclusions fail in this pattern.

fallen tree