Does a Philadelphia tree or shrub need pruning?
We are assuming that you are referring to Philadelphus, or mock orange. According to the Missouri Botanical Gardens, flowers appear on prior year’s growth, so prune as needed immediately after flowering. They may be cut to the ground (also just after flowering) if shrub becomes scraggly, unkempt or otherwise in need of rejuvenation.
For further information on this plant, please see https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspxtaxonid=268920&isprofile=0&