You may have already done this, but if not, now is the time. In order to encourage many more flowering shoots from perennial Chrysanthemums, pinch back stems to 4-6″ at the beginning of July. This encourages more stems to shoot resulting in many more blossoms, and perhaps tidier plants. (Of course, if you prefer the blousy look of tall stems that billow forth, by all means leave your plants be.)
You can also cut back the taller fall Asters and their relatives, such as Boltonia, to keep them neater and in proportion to their surrounding neighbors. For example, Aster ‘Vasterival’ reached 5′ last September, and it was just too much Aster for the nearby Caryopteris and perennial mums.