I have attached a picture of the area I have. I have decided on three dwarf Bonanza sasanqua for this spot. The area get mixed shade in the center and mixed sun on the edge. I am going to put the sasanqua in almost the identical spots as the hydrangeas.

My question is.. whst do I do with the remaining 3-4ft of edge line before the grass starts!? I can let the grass grow but it's going to take a while. I have hosta on the inside of this bed.. so what would work in front of these sasanqua, maybe some summer interest that can handle slightly mixed sun but definitely not full sun.

The distance between the two large trees is approx 14ft so if you walk the distance of the outside edge it would be apprx 16ft curved.