I just love purple and orange
I have several clumps of Mainacht--never had any trouble with flopping, although I have squished a few by overcrowding with more aggressive and bigger plants. I don't really call that flopping when a plant has to grow under another one and over and out to find the sun. I guess I think of flopping as something that was tight and upright suddenly splaying and falling over all on its own accord like a peony or something
but maybe I don't know what flopping is?
These are a couple of 5 (on the left) and 3 (on the right) year-in-this-spot clumps this past spring--both are really quite massive. I used to have them along the sidewalk but they got too big so I moved them into this garden. They are about 30 in tall and about 40+ in wide.
I do typically cut them back after the spring peak, but they are still blooming and branching and budding and because I like to keep the bees fed
I am not very drastic with cutting and I let them get pretty ratty looking.
This year I cut one (that I have in a different garden) back to the ground after the spring bloom because it was crowding something else--I was amazed at how well it grew back and how nice it looked in August and September
I may have to try some more drastic pruning next year.
All in all, these are very resilient plants in my area and I find them to be full sun appreciative, quite drought tolerant, care-free bee feeders