Inner ring MUST have a layer of large river stones for air +water to get to trunk, otherwise it will suffocate + kill the tree. The soil will support small shallow rooted plants like Allyssum or Primrose.
A raised bed for the garden is a nice way to plant vegetables and herbs. You have an easy access to the plants in the raised gardening bed and save your back while working in the garden. You don't hav(Diy Step For Bed)