In 2014, the Arboretum volunteers teamed up with iTree and Treeconomics to carry out a survey of the valley’s trees.

Ten years on, we will be repeating the survey during 2024, this page will develop as the process moves forward.  Please contact us if you are interested in helping.

Using a computer generated sample of 200 circular plots, volunteers collected data on all the trees within the 7m circles, including which tree species were present and how big the trees were, girth and height.  The sample data was then sent off to the US Forestry Department for analysis.

The Survey Plots

It turned out that our valley was home to just over 400,000 trees in 2014, with nearly a quarter of the valley under tree canopy.  The three main species were the commercial plantations of Douglas Fir and Larch with Ash as the most common native broadleaf tree.  It was noted that, even in 2014, the Larch and Ash trees were under threat from two new diseases, Phytophthora and Ash Dieback.  In 2023, most of the Larch plantations have been removed and significant numbers of the Ash trees have been felled.

We plan to repeat the survey in 2024.  If you would like to be involved, please get in touch via

A summary report on the survey can be seen if you click tree_survey_report_v6.