The UK's National Willow Collection was set up in the aftermath of WWI when a War Office review identified there had been a shortage of willow to make containers for ammunition. 100 years on, plastic is now used to do many of the jobs willow once did. But the collection is now run by Rothamsted Research, where scientists are looking at the potential for new materials to be made from willow that could replace plastic. In this programme, Sarah Swadling visits the Collection, which has over 1500 different willows and celebrates it's 100th anniversary this year. Presented and produced for BBC Audio in Bristol by Sarah Swadling