I don't live in your zone, but zone 7. I prune, or trim mine back to almost the ground in fall, sometimes the spring. In summer it gets to 5 ft. tall. I suppose that yours has roots that are well rooted, and will sprout new shoots then. The pruning stems I take, and put them in a pot with deep soil, and thus, get new plants. I have sent them all over the US, as they root quite well. The one I have is Mrs. Popple.
Darlene

It depends on the species or specific hybrid - some grow to be very tall. I had a F. magellanica 'Molinae' that was about 12' tall with a massive 6" trunk. I pruned it back each season to about 6', sometimes shorter depending on the severity of the winter and the amount of dieback. It did sometimes produce new growth from the base, but it was often spindly and I generally removed it.