The edge is photosensitive. I have mine planted so that it will get some morning shade from a Japanese maple tree, once it matures. (This is the third such tree we've had in the same spot now, the original much larger tree (which did shade the clump), and a successor, having died - probably due to inadvertent over-watering.) When I picked the last two blooms late yesterday morning, one still had a hint of an edge, the other did not.
My big problem with this plant (apart from the disappearing edges) is that there are almost always one or two tepals that are cupped, and have to be prodded back into place. A lesser problem is that the blooms don't always open as well as I like, and here they don't reach 6", but that could be a combined result of drought (we are on watering restrictions) and overcrowding in the humongous clump (well, 3 clumps jammed together, since Warp helpfully divided the original one).
The one big boon of this plant is that it is rust resistant.
Right now, I am actually weighing whether to keep the plant (I am tired of poking and prodding the blooms every morning, and I want larger flowers) or to pitch it (but it's such a large clump! and it's rust resistant! and you know you'll regret it!).
