Philadelphus Mock Orange is a genus of deciduous, summer flowering shrubs belonging to the Hydrangea family. Hardy down to USDA Zone 4, Mock Orange has a multi-stemmed growth form that requires occasional pruning to remain full at the centre and bottom of the plant. It should be pruned in the late summer or early fall after flowering has finished for the year.
Prune away broken, dead, abrading, diseased or otherwise problem woody tissue or foliage throughout the year. Cut back to a point of healthy plant tissue, down to the parent branch or soil line as needed.
Rejuvenate the interior and lower level of the shrub every few years or as needed. Prune out roughly 1/3 of the oldest, barest branches at the crown of the plant, at the soil line. Pull the full branches free from the shrub as you work. Distribute the cuts throughout the base of the plant so that new bushy growth fills in evenly.
Reduce the perimeter height spread of the shrub by trimming back the terminal branch tips as desired to better suit the planting site. Work around the shrub evenly, following the natural form. Take up to, but no more than, 1/3 of the shrub tissue in any one pruning session.