>>519278The best are small-leaf trees. Those respond well to making their leaves even smaller as you make it into a bonsai. That is why juniper is a good one. But, most any tree can be used regardless of style.
Most yamadori are many years old and already semi-bonsai from the harsh surroundings or their species traits. You will need to wait until the next Spring before the buds have sprouted. Dig it up then. In the mean time you can tag the tree and start planning how to care for the tops as well as research.
In case you don't already know, it normally takes at least a few years of open-ground growing and healing before putting a tree into a bonsai pot. Especially, if it was grown from a seed or young cutting. Which is why yamadori is quite popular. The trunk and bark are usually already aged quite a bit and look aesthetic. You shave off many years of time to get a final product.
Take this future bonsai of mine, in this image. It is around 8 years old. I started it from a cutting in 2007. It needs to grow in the ground for a long time to get nice girth and bark texture. I am supposed to dig it up every single year to trim and shape the roots. I'll be trimming the branches soon, leaving only the ones that will take shape for the limbs. It may be in the ground for another 10 years just to develop good-looking bark on the currently absent limbs. A yamadori can help you skip much of this phase of development.
