The Hamburg Tree Pruning System

"Trees in urban areas are pruned for many reasons. Each pruning cut causes a wound, which leads at least in the exposed wood at the wound surface to discoloration and decay. The extension of the resulting defect depends on wound diameter, tree species, time of wounding, wound treatment, and last but not least, the attachment of the branch to the stem. The effects of different pruning cuts on urban trees has been investigated in Hamburg, Germany since 1985. The study of 750 different pruning wounds on typical urban tree species led to the Hamburg Tree Pruning System (Hamburg Schnittnethode). The system is described in this paper and answers the follwoing quetions: How should branches with or without a branch collar be removed? How should dead branches be removed? How should branches with included bark or codominant stems be removed? What are the differences between tree species in wound response? What is the maximum wound size which will be effectively compartmentalized by the tree?" [Abstract]