Phlox paniculata is one of the mainstays of the mid-summer to early fall garden. Commonly referred to as Garden Phlox, this upright native of the eastern United States is usually magenta-pink. The species is rarely seen in gardens because the selections are so superior in floriferousness, vigor, and mildew resistance. These selections and cultivars have an extended color range with the exception of yellow and blue. Although some of the cultivar names say blue, there is yet to be a true blue.
Garden Phlox, in average soil, moisture and full sun, will grow two to four feet tall. Good air circulation is essential although not a cure-all to prevent powdery mildew; thus, spacing Phlox paniculata two feet apart is highly recommended. Additional methods of assuring good air movement are thinning a clump to only four or five strong stems and watering only at soil level in order to keep the foliage dry. If overhead watering is necessary, water early in the day to allow time for the foliage to dry before evening.
Deadheading immediately after bloom will encourage more blossoms on lateral branches. After the laterals have bloomed, pruning down to the next set of laterals will encourage further bloom. The first terminal blooms are usually quite large and dense. Later blooms become successively smaller. The linear foliage is two to five inches long with a slender point at the end.
Among older cultivars, the literature indicates that the cultivars ‘Bright Eyes’, ‘Franz Schubert’, and ‘Katherine’ are fairly mildew resistant. ‘Bright Eyes’ is pale pink with a crimson eye while the other two are lavender. Then along came ‘David’ who was the star for many years. However, even ‘David’ occasionally has mildew.
The only phlox on which I have never seen mildew is ‘Blushing Shortwood’, a pale pink cultivar that is probably a hybrid of ‘David’ and ‘Shortwood’, a sport that is rosy pink with a touch of magenta. I have also been impressed with ‘Glamour Girl’, a 32” vivid pink, that has illuminated one of my back beds for the past four years.
In the past few years, two new series have been introduced that are extremely mildew resistant. One is Candy Store®. Among its cultivars are Coral Crème Drop, Grape Lollipop (magenta with white starburst center), Bubblegum (bright pink), and Cotton Candy (soft pink with dark pink center). I’ve only grown Coral Crème Drop so far but have been delighted with the coral pink color and the lack of mildew. The phloxes in this series only grow 18-24”.
The other relatively new series is Flame™, the selections of which grow 15-18” high. They are named by color, i.e. Light Pink, Lilac, Pink, Purple, and Red. I haven’t grown any of them but the reports on them are very good.
Phlox are so easy to use in the garden. One of the taller cultivars could be used at the back of a perennial border with a medium-sized mounding ornamental grass such as Pennisetum alopecuroides (Fountain Grass) in front of it and one of the coneflowers, either Rudbeckia fulgida ‘Goldsturm’ or one of the new, shorter Echinacea purpurea cultivars beside it. A medium height Phlox paniculata cultivar could be used against a background of Miscanthus sinensis ‘Adagio’ (only 4’ high) with Aster ‘Purple Dome’ or ‘Vibrant Dome’ beside it.
The only drawback to phlox is that the deer seem to find the foliage very tasty. However, on the plus side, the plant will be shorter and bushier.
Plant the new mildew resistant cultivars of Phlox paniculata and keep an eye out for more new ones yet to come. Make yourself happy with this beautiful perennial; it’s too good a plant to evict from our gardens now that the mildew problem can be combatted with the right cultivar rather than fungicides.