Answer: To my knowledge these plants are always propagated by seed; I am not aware of any suggested procedures for taking cuttings. You could conceivably make root divisions in early spring, but that might risk the mother plant due to the root disturbance.
To be honest these are just plain straggly plants but they do appreciate plenty of water and seem to stand up better longer when they are in a fairly moist situation (they are swamp plants originally). They also prefer full sun along with the moist spot, so you might try one in that type of location and see if there is some improvement. You might also try interplanting them with something else that will help camouflage the lanky stems. At least the flowers are gorgeous!
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