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For masses of color in your flower beds, long-blooming phlox is hard to match. Many varieties are pleasantly fragrant, make terrific cut flowers, and attract butterflies.
But the beauty often comes with a price. In many gardens, phlox is blemished by powdery mildew, a grayish—white powdery growth that begins on lower leaves. By late summer, these leaves are often dying, and many of the top leaves are covered with powdery mildew as well.
You can reduce mildew by spraying with an organic horticultural oil; however, the best long-term solution is to plant mildew-resistant phlox cultivars. Resistant plants are not totally immune to disease, but they do possess characteristics that will keep the mildew from taking complete control.
In my own North Carolina garden, Phlox paniculata 'David' and 'Robert Poore' have the most resistance to powdery mildew. 'David' has sparkling white flowers; 'Robert Poore' has magenta flowers. Both perform spectacularly and have had hardly a spot of mildew on their leaves.
Researchers in a variety of locations—at the Chicago Botanic Garden, at the University of Vermont, and on Long Island, New York (in conjunction with Cornell University)—have screened dozens of available phlox cultivars and identified those that resist powdery mildew in diverse conditions.
You can count on these sturdy varieties to anchor your garden for many years to come. Just be sure to plant them in full sun in rich, well-drained soil. Keep them watered during dry periods, and cut back spent flower heads to promote a second flush of blooms.
