Hi Judy, Can you add a pile of fresh soil or compost on top of the stumpy ground? That would be the best solution for the area that you want for a flower garden. As for the area you want to add a tree just dig a hole twice as wide as the root ball of the new tree but don't worry about going any deeper than the pot the new tree came in. Remove the old roots and any large rocks from the planting hole using a saw if necessary to get rid of the old tree roots. The new tree roots will spread out ward more than they spread downward and if you add a mulch and keep the tree watered the first summer it should be fine.