The Hampton Hack.

                  

Many of these earlier flowering perennials can be happily cut back hard once they’ve finished flowering, around early July. At the very least doing this can promote fresh growth that remains tidy for the rest of the season, without distracting from the broader display. 

Sometimes, rewards are richer still with plants repeat flowering before the season is out. There are caveats: any repeat blooming will be less impressive than the first and to power all this re-growth it is particularly important to feed and water plants well after chopping them back. If you are in the middle of a drought it may be best to wait.

How and when to Hampton hack

When the last flowers have faded, take some shears and remove the top growth, usually to within a few inches of the ground. If you are hoping for more flowers, the sooner this is done, the better. Tidy up, then water the clump and fertilize lightly. A light mulching is helpful.

Have a look: https://youtu.be/a_fTqY26k7Q?si=_KjVSe1UPZ0IK2UL