Bonsai Empire has a video featuring International Bonsai Master Peter Warren titled “Selecting yamadori material for Bonsai, Peter Warren“. Peter gives some excellant advice on buying or collecting yamadori trees. I bought a yamadori from a local nursery when I first started Bonsai in 2009. It was a cute Ponderosa Pine tree, I discovered latter after it died despite my efforts to save it that it had no roots on it. In fact it was no tree at all just a branch stuck down in some clay soil and then balled and burlapped. My mistake was buying it at the local nursery and should have bought a tree from an experienced collector. Peter talks about this and what actually makes a good yamadori as most trees are not collectible. I have added the video to the Collecting Trees For Bonsai under Bonsai Basics page.