It was a sight to see. The trunk of a black locust tree (Robinia pseudoacacia) floating over the Arnold Arboretum! This rogue unaccessioned (and declining) tree planted itself in the living collections of the Arboretum some decades ago along the border with Centre Street. Yesterday, its crown was removed and the entire trunk was lifted into the air by a crane (left image). This tree, along with a couple other declining black locusts, were then moved to the old stone quarry on Bussey Street that serves as the Arboretum’s mulching and composting headquarters (upper right image). Here, the trees were milled into boards (image lower right) for a new foot bridge being constructed to provide access to the conifer collections across Spring Brook. Imagine, growing your own bridges!

black locust trunk moved by a crane at the Arnold Arboretum

Black locust is certainly a familiar tree in Massachusetts, but is not, in fact, native here (or anywhere in New England). Indeed, it is on the Massachusetts Prohibited Plant List.  Its northern-most native range was probably central Pennsylvania, but it has escaped from cultivation and become naturalized in many places (around the world). The wood is incredibly rot resistant, making it ideal for fence posts, as well as handcrafted foot bridges in the Arnold Arboretum. 

This past spring, colleagues in the Graduate School of Design at Harvard (Professor Kiel Moe and two of his students, Peter Osborne and Iain Gordon) proposed the idea of designing new foot bridges for the Arboretum—with a central tenet of sustainability and locally sourced wood. By the end of next week, you will be able to walk from the beech collection right into the juniper collection across magnificent boards that captured carbon from the atmosphere right here in Jamaica Plain and locked it into a bridge.