You can trim them back now but don't wait much longer as pruning will encourage new growth which will not be winter hardy.  Depending on the look you want, you can either cut the thickest stems to the ground, allowing for new growth from soil level.  If you are trying for a tree, then cut back the newer thinner branches.  The recommended time to prune is immediately after they bloom as they will be setting next spring's blossoms at that time.  If you prune later, you will be losing the fruit.  https://extension.umn.edu/planting-and-growing-guides/pruning-trees-and-shrubs

You do not need to cut them to the ground.  You can cut some of the larger stems to the ground but just trim back the rest by 1/3 or so or at least to a more manageable size.

Thanks for the info.