I have several clumps of Stella that are hardy as all get-out, and several more of a non-registered red I fondly call 'Rusty Dupuis' (in memory of a co-worker). I typically just let the foliage die back on its own, but will choose two clumps to cut back hard and see what difference there might be. The red is a bit later than Stella and is still looking OK but Stella is definitely in the dulldrum stage. The others I have are not as mature so I'll just let them die back on their own.
