Although certainly not a requirement for any evergreen varieties, they can be cut back hard. And in fact, it is recommended to do so before dividing........which looks like it may be of benefit to your plants. They look overly crowded and congested......are they still blooming well? It sure wouldn't hurt to thin things out a bit and maybe do some soil improvement before replanting.

Here is what I have done so far. Next year I will do the dividing. You can still see some of the roots that are growing within the plant. I still have more to cut down.

Hi Nick, how did this work out for you? It’s time for us to do some hard cutting and dividing over here.