The Q&A Archives: Phlox Dying

Question: I have tried several different varities of garden phlox (David, and others) in my perennial bed in several different locations with the same results. The plants begin the early spring healthy and with strong growth. Then into later spring the leaves begin to turn yellow with dark spots starting at the bottom of the plant. The wilting and discoloration of the leaves spreads up the plant. The leaves drop off and finally the plant dies. I am an organic gardener. I certainly hope you can help me. I appreciate phlox's bloom time in later summer and have a neighbor who grows them successfully. I have tried every method (organic) to try and save them, to no avail.

Answer: The tall garden phlox are wonderful in the border, and "David" in particular is known to be one of the healthiest and most resistant types. But as you know, these plants in general are prone to problems. I have several suggestions and observations. First off, phlox grow best in a rich soil which is both moist and well drained. Adequate moisture is very important to keeping the plants healthy. However, you should avoid getting moisture on the leaves when you water. Second, it helps to divide the plants often, perhaps even every other year, and to thin them ruthlessly to only a few stems each spring. This helps keep the plant vigorous and allows air to circulate through the plant. Try to place the plant in the garden in such a way that air can circulate around it from all sides. This may require that you plant only shorter plants nearby. Be sure to provide plenty of space for the phlox to grow into and fill during the course of the season. Finally, maintain an adequate layer of mulch around the plant and be meticulous about cleaning away all of the phlox debris after the killing frosts in fall. Lastly, do not replant phlox into the same spot where it grew and failed to thrive previously and be sure you are starting out with clean healthy plants. I wish you great success with phlox this summer!

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