@ge1836
okay--I get it now!
or at least I think I see what you mean.
In addition to redesigned fortification, my suggestion would be to increase the area a little--if you can --so that it's not right on the edge and the irises have room to expand-- that way also if you don't succeed right away in 'stabilizing the edge' it is not quite as critical.
But I don't have any idea of the 'lay of the land' there...maybe level it out and plant it deeper?
Merry Christmas
