Phlox paniculata, or garden phlox, is a tall perennial plant suitable for the back of a flower bed or in front of a building or fence. The large, scented blooms display from July into September. The David variety of phlox paniculata produces pure white clusters of blooms. The Perennial Plant Association named David perennial of the year for 2002. You can prune phlox paniculata to encourage more blooms, control appearance and for seasonal cleanup.
Plant phlox paniculata at least 24 inches apart. The plant can reach widths of 24 inches. By planting at a distance of at least 24 inches from any other plants, more area is provided for air circulation to help ward off mildew.
Prune or pinch back about one-third of the stems in the spring. Pinch down to the first set of leaves. This type of pinching back will result in blooms showing on the pinched stem after blooms have occurred on other stems to provide a continuing floral display.
Prune out stems in full plants in late spring to open up the plant and subsequently allow other stems to produce larger blooms. Choose one stem in every three to five stems and cut it to the ground.
Prune out blooms that have faded by snipping the bloom off just under the head of the bloom or anywhere down the stem.
Prune down to the ground after the plant blooms or in the fall.