Question WHEN IS THE BEST TIME TO PLANT CREEPING PHLOX? Answer Creeping phlox is a tough plant! You can plant it either spring or fall. If you plant it now, you will be able to enjoy it early spring when it flowers. Tags: CareDesignFAQProjects Related Questions Do next years blossoms come on new or old growth? My hydrangea plants appear healthy each year however, they do not produce flowers. What to do? What are the dark spots on the leaves of my hydrangea? My roses aren’t thriving. What can I do?