For his book The Man Who Made Things Out of Trees, Robert Penn set off across Britain and beyond in search of craftsmen to help him fashion an extraordinary variety of artifacts—including a toboggan, a hurling stick, and a Louisville Slugger baseball bat—out of a single mature ash tree. He spoke to National Geographic about the importance of these imperiled trees from his home near Abergavenny, Wales.

I grew up under an ash tree. It has been my favorite tree all my life and, in many ways, it’s been a lodestar that has guided me on my journeys around the planet. It led me to live here in South Wales, in a landscape that is heavily accented with