I have a 3 ft stump of a green ash tree that I pulled out of the ground. I cut 3 root stubs with a chain saw. It's coming from a triple trunk that was rotting out. Is there any way I can regrow the roots where I made the cuts? I'm trying to bonsai the tree. How can I get the roots to grow? The root stumps are 3 inches thick. Thank you.
If you're expecting a piece of cut trunk from an ash tree to develop roots, I'm sorry to tell you it's not going to. Now it's been cut, it's in the process of drying out, so effectively, its already dead. Which is probably just as well, because if its an ordinary ash, they have large composite leaves, and are not ideal subjects for bonsai.
You can grow your own bonsai from seed - you just need to think about what plant you want in relation to where you are going to keep it. Indoor bonsai plants are different from those that need to be outdoors for most of the year. Some information in the link below