I want to plant a few hostas around a tree in my garden, but the roots are in the way of digging the holes. Will I damage the tree if I dig through some of the roots?

Most likely would not be good for the tree , but if the roots are so tight I am sure the Hosta would not do well for long. Do you have pic if area so we might be able to come up with some ideas.

The tree is a Japanese Cherry tree. The Dusty Miller is coming out soon.

If you were able to plant the Dusty Miller there you should be able to put a smaller Hosta where it was. Does not look like there is room for large ones by the pic provided.

I guess I'll try to dig some holes very carefully and see if I hit any roots. Thanks!

Hope it works for you.