|when and how to cut mums back
|Mums should be pinched (pinch off the individual growing tips by hand) or lightly trimmed every two weeks or so from spring until the fourth of July as a rule of thumb. This helps them grow bushy and dense and causes the plant to have more flowers as a result. It is a bit late to start but you might try cutting it back by about a third, then pinch the new growth tips a few times. Stop pinching in late August. This may cause them to bloom a bit late in the fall, but will keep them from getting so leggy and thin.