I've always left them alone and cut them back after the stalks die in the late fall/winter. The reason I did it this year is right after the peonies reached their height, they blocked the view of my front door from the street and lo and behold someone tried to break into my door while I was at home. It scared me bad and I've been itching to prune back those shrubs. So I did it. I know...they won't bloom next spring. I will move them to a new location next winter or early spring and then have to wait for flowers the next year after.

It's a shame because every time I look at those shrubs now, I equate them with the attempted break in and not my beautiful flowers. But it's time to give them a better location. Thank heavens my dog ran off the intruder. I am now making sure my garden does not block the view of my front door and making adjustments accordingly.

The foliage helps to increase the size of (and I expect number of eyes on) the rhizomes, however it doesn't necessarily impact the existing bloom potential if removed too early after bloom.