Question
I had three large trees removed and the stumps ground out two years ago.  The area keeps sinking and it mostly mulch up to a foot down....what can I plant there?

Answer
What happens when a tree stump is ground is the stump is ground down to about 18-24 inches below the soil surface and "hole" is filed with the chips. As the wood chips decay the area sinks. You can fill the sunken area with good top soil and then plant about anything you want. I would plant a tree a little to the side of the old stump , that way you will not hit the old stump as you dig down. The one draw back is the decaying wood chip will use a great deal of Nitrogen from the soil and you will need to fertilize the new plant with a nitrogen fertilizer to off set the amount lost. But you can plant any species of plant you want.