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 Can I mix lime in the dirt when I plant my hydrangeas to keep them pink and red? My Summer Crush is totally brown in the original pot I purchase it in. Please help. I thought it would come back this year and I would plant in a flower bed. What type of fertilizer is the best or is blueberry fertilizer just as good? If I add more soil acidifier to Endless Summer blue, will it make them darkest blue or purple? They are a medium blue now. I’d like purple! Love my endless summer, thank you.