I established a black walnut Juglans nigra improvement programme while I worked with the Northmoor Trust in the mid 2000s. I was lucky to visit the USA on a couple of occasions as part of this work, where black walnut is an indigenous species and a significant timber tree.
I took part in two symposia of the Walnut Council where I presented papers. On my first visit, some of their leading researchers and growers laid on a fantastic tour across Wisconsin and Indiana. I visited the Hardwood Tree Improvement and Regeneration Center of Purdue University. I met over one hundred passionate walnut growers, including Senator Dick Lugar in Indiana, saw so many wonderful woodlands and was throughly looked after by fantastic hosts.
These visits laid the foundations for a black walnut tree improvement programme for the UK. Black walnut is economically one of the more productive broadleaved timber species in Britain. However, it is also one of the least-planted species. There was insufficient knowledge about the species among foresters and very little, if any, improved material was available.
I arranged a range-wide collection of seeds from plus trees and populations in the USA (Alabama, Illinois, Indiana, Iowa, Kentucky, Maryland, Minnesota, Missouri, North Carolina, Ohio, Pennsylvania, Tennessee, Wisconsin) and Europe (Austria, Czech Republic, France, Great Britain, Italy, Serbia and Montenegro, Slovak Republic). I planted two field trials in Britain during 2003/4: at Paradise Wood in Oxfordshire, and at the National Forest in Derbyshire.
Clark, J., Hemery, G.E., Russell, K. & Williams, H. The future of black walnut in Britain. Quarterly Journal of Forestry 99, 207-212 (2005).