In March 2021 a large oak tree fell from the East border across the East Walk completely blocking the path. There was not any extreme weather that night, but the tree was quite asymmetrical in its growth. The branches of the tree crushed one of the maple collection, Acer triflorum (see description in the tree archive) Examination of the tree rings showed a very reduced growth after 2011 with almost no growth in the last 2 or 3 years, so the tree was clearly under severe stress before it fell. 
The tree-ring widths for the whole tree were measured on a slice of the stump and dated by dendrochronology. The outer year that could be distinguished was 2019 and the innermost ring was dated to 1831. As the land for the Botanic Gardens was purchased in 1828, it is likely that this oak was part of the early boundary planting. 

Photos taken in Belfast Botanic Gardens in 2021. Copyright: Friends of Belfast Botanic Gardens.