I trimmed mine back after bloom last year, and this year is the best I've seen them. I shaped them into smaller oval or circles by just giving them an all over haircut. I can't remember if I waited until all the bloom dropped off or not. I do credit the mild winter we had too, for how well they've done this year. I usually have to cut off more winter kill than I had to this year. I would think right after bloom is the best time to divide any early spring blooming plant. I'd be interested in what everyone else does too.

Also interested. I didn't trim one of my phlox last year and its huge this year, almost cascading over a stone wall and blooming just as well as the ones that were trimmed.

I think the trimming is sometimes about space available. I don't have a stone
wall for it to cascade over. Just a short edging, so if I let it get too large, it looks pretty messy. But I have seen great looking specimens coming down over walls and they look great that way.

Thanks for your input..There are some that were so full that they had grown over the scalloped brick pavers and onto the sidewalk so those really need to be cut back, maybe dug up and divided..I'm thinking of starting some over on the hydrangea flowerbed..I will need to study the sun's exposure before I move them. Plant them along the edge in between the hydrangea that have a wide spread factor. After that hard freeze last month that hit the hydrangeas bad, don't know what they will look like this summer. Hopefully they will bounce back.

Maybe I can sheer them back today and maybe dig a few up and divide them, potting the divided sections into potting mix to take to the upcoming plant swap..

I have a fair bit of success rooting soft cuttings, taken just after flowering.

I am curious if shearing and dividing right after flowering works well with these; that is also what I am thinking of doing :).

I also started some cuttings in a soiless mix a few days ago, with a bit of root hormone (which might have been overkill with phlox since bits of it seem to root all over anyway).

I love that it grows down over my stone wall, but I need to keep it at the front of the garden-- not strangling the echinacea three feet back! :)

Plus I am looking to divide so I can use the same species in other areas of my garden to increase continuity, which is a focus in this my third year of gardening at this house. Repeating colors (silver and lime foliage, purple and blue blooms, spots of apricot and orange color), and now looking to propagate and divide so things are more repeated and uniform. [Rather paradoxically, I'm trying a lot of new species from seed at the same time, haha.]

Whoops way off topic now -- anyway, I'll be dividing mine as soon as they fade! Good luck.