you can get around the floppiness of many tall plants like aster and frost weed by cutting it in half mid season. Cut the debris in pieces and leave it there and you take care of mulching as well. Nothing is better than blooming aster with a pumpkin sitting by it and a scarecrow sticking out of it with all the monarchs flying around in the fall.
Every source I read talks about how aggressive conoclinium coelestinum is in a small space. I wonder if the info is just circulated around from source to source.
That's just a general observation. It depends on the site -- soil, light, plant competition. Put CC in a rich loam marooned from other plants and yeah, aggressive. Put CC in sun, other aggressive species around it, in dry shade or part shade (again with actually plant competition / plant community), it acts as a lovely filler and shoulder season bloom (late August). Also may depend on your ecroregion. Lots of variables! Gotta do your research.
