Dear "Bama Boy":
For my dioramas I go to the local model rail road hobby store to get artificial dirt, grass & trees. If by chance you are trying to show a Sudan War, etc diorama(s) you should get a 25 pound of "PlayBox" sand that will cost only about $3.00 or so at a local Garden store. In at least one case where I had sand on the display table, but then I later wanted to convert over to have a diorama calling for grass I just left the sand there and placed the "grass" over the sand. The advantage being that I did not bother with removing all that sand and also the sand acts as a nice medium to "seat" the figures into place. Also, do not forget that you can use small stones & twigs from your yard outside your home for your dioramas as well.
"iron Brigade"