Mockorange (Philadelphus coronarius) is a favorite blooming shrub. Who wouldn't be attracted to the lovely white flowers and their heavenly fragrance? Some gardeners can get mockorange to grow and bloom with no effort, but other gardeners coddle it endlessly with no luck. Here are some reasons why the shrub may not bloom. Improper pruning. Prune mockorange right after it blooms. If you prune it after midsummer or before it blooms in spring, you could be cutting off the flower buds. Freezing temperatures. Mockorange produces flower buds the year before it blooms; the buds could freeze over the winter if is is a variety not suited for your climate. Likewise, late-spring frosts could nip off the buds. Too much shade. Although mockorange can tolerate some shade, it won't bloom well if it gets too much. Remember that a sunny spot can gradually become shady as trees grow larger.