Risk, damage, and the cycles of the Moon

This current issue of the Arboricultural Journal gives me a mix of excitement with respect to three excellent and very different but insightful papers, but also of sadness as we pay tribute to the late Rodney Helliwell, who passed away after a long illness earlier this year.

We have three papers taking contrasting views of very different topics. So for example, Helen Read and colleagues (2018) have been researching the supposed influence of moon phase on the cutting of lapsed pollards in Spain. This is something which the charcoal makers in Navarra put great importance on when deciding to prune their trees; the correct moon phase is considered to be vital. Apparently, beech trees should be cut in a waxing or growing moon. To test the theory, a small group of lapsed beech pollards were cut back close to the bolling in either a waxing (con luna) or waning (sin luna) moon. The researchers then assessed the growth responses after four and six growing seasons. As so often the case, the work answers some questions but raises others.

A very different piece of research is presented in the paper by Jeffery Van Treese and co-authors (2018), when looking at the importance of highway trees and their potential influences on car-driver responses. This is fascinating and indeed important work. It is suggested that roadside trees help calm traffic, define roadways, and reduce driver stress. Nevertheless, as will be appreciated by many urban arboriculturalists in particular, roadside trees were also common components of urban infrastructure that are involved in single-vehicle crashes. The researchers used conjoint analysis to assess driver perceptions of risk associated with roadside trees, road geometry, vehicle speed, and lighting conditions. The research took place in Florida where drivers were shown videos of street scenes with randomised variations of the four key attributes. They were then asked to rate their perceived risk. From the study, it appears that drivers perceived trees in close proximity to the highways as increasing risk. Additionally though, night-time conditions with supplemental lighting slightly reduced perceived risk. Again, there is much here that could be followed up.

Harry Thacker, Jaime Martin, and Duncan Slater (2018) provide a good insight into damage to trees in their process of establishment. In this paper, they report on a London-based case study into damage inflicted on establishing trees by a range of tree support and protection systems. Overall, they found around 345 of planted trees were damaged and in many cases this was because of a failure to follow-up and remove the kit used to provide initial support. This comes as no surprise, but it is very useful to have real data to backup a supposition.

We also include in this issue a substantial review of Mark Johnston’s important and timely, recent book Street Trees in Britain which follows on well from his excellent, Trees in Towns and Cities. There is also an obituary for the late Rodney Helliwell.