Answer: As a rule these plants are very pest and disease free. In my experience, both overfed plants and mature plants in need of division will splay open much as you described. You will find that bits of the stem and foliage will in fact try to root as if to colonize the area around the original plant. Some gardeners will trim back the plant early in the season if it appears it is likely to flop, but once a plant has done it about all you can do is plan on dividing it in the fall and possibly take plenty of stem cuttings now to tidy it up a bit.
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