I am going to look at a some planters that have crepe myrtles in them. The manager told me they cant see any annuals from the street because the soil level is too low. I can't bury the trees so I was thinking about building a ring around the tree with maybe plastic edging, then add soil around the outside of the ring. Anyone run across this? I definetly don't want to raise the tree if I don't have to...not enough money in their budget.