Urban Tree Mortality: The Purposes and Methods for (Secretly) Killing Trees Suggested in Online How-To Videos and Their Diagnoses

Abstract Background While urban trees offer numerous environmental benefits, some people view them as nuisances due to ecosystem disservices like smelly flowers, messy fruit, leaf litter, and damage to infrastructure. Because some trees are protected under ordinances or are owned by someone else, some people resort to covert methods to eliminate them. To assist arborists in identifying these clandestine practices, we investigated YouTube videos that suggest methods for secretly killing trees. Methods Using established methodologies for YouTube reviews, we used search strings such as “poison neighbor’s tree,” reviewing the top 100 YouTube videos per search string based on relevance. After filtering, 79 videos were analyzed through deductive and inductive coding to classify tree-killing methods, the purpose of the method (e.g., wildlife habitat creation), and potential diagnostic signs and symptoms for arborists. Results Herbicides were the most frequently suggested method, with glyphosate commonly referenced, followed by girdling and salt. Some videos emphasized secrecy in framing, yet none discussed potential legal ramifications. The methods often left physical signs, such as trunk damage from girdling or residue from salt application, which may aid arborists in detection. Conclusions Our findings underscore the need for diagnostic tools that help identify subtle symptoms of poisoning or mechanical harm in urban trees. This study serves as a foundation for further research on tree-killing techniques, supporting forensic arboriculture and the remediation of intentionally damaged trees.