I trim mine back more than that but I only do mine every other year so have to make it good. This year I pruned them in early April and they're about eighteen inches tall now.

To my way of thinking the goal is to open them up for air flow and so the sun can penetrate as well as controlling size- I'm not fond of "shearing" where all one does is shape the outside of the plant while leaving great wads of tangled branches within. I like to get in there at the base and try to direct future growth with
my pruning cuts to make each year easier. But I will tell you that I have so many spirea that I often get frustrated and just hack them down- spirea
are very forgiving. But I still do it in a 'pruning mode' not a 'shearing mode.'

Every year your pruning skills will increase and bit by bit you can get them back into shape. We bought this place in '07, moved and divided all the spirea that fall, and in a couple of years they looked well established again.

just like your tree question.. where a giant stub was left ... you left a lot of dead stubs on these ... but hey.. we were all new at it.. back in the day ... good first try ...

give them a week or 3 ... to see how they rebud ... and before that growth gets to long.. trim back any dead spikes you left ... just clean it up a bit ..

ken

Ok..you almost have to prune out the suckers...gonna take a while...thanks.