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 How do I plant little devil ninebark? What do I do for fall care? My hydrangea plants appear healthy each year however, they do not produce flowers. What to do? I planted 3 Endless Summer (Summer Crush) last summer. However, during the later part of the season there were holes on most of the leaves. I think there are some pest. What should I do to save my hydrangeas and when is the best time to do it?