First - do you deadhead the flowers? Second - next spring when they come up, can I cut the tops off to make them branch out. Mine are one flower on one stalk. Thank you.
Tall Garden Phlox
Certified GKH Gardening Expert
You can go ahead and cut them back anytime after flowering has stopped. Deadheading them may even promote additional flowering. Here is more information: https://www.gardeningknowhow.com/ornamental/flowers/fgen/deadheading-flowers.htm