Tall garden phlox (Phlox paniculata hybrids) provide one of the best summer flower displays in the perennial garden. Often a favorite in cottage gardens, tall garden phlox can bloom as much as six weeks, come in a variety of colors, and many have a sweet fragrance. Some cultivars begin their flower display in mid-summer, others not until August. These plants are hardy and vigorous when grown in the right conditions.

Site and soil

You can buy tall garden phlox as bare roots, but potted plants are easy to find. Be sure to buy Phlox paniculata. There are other phlox species that will have different growth habits and growing requirements. Grow tall garden phlox in full sun. Avoid placing plants too close to fences and walls where air circulation will be poor; this can be an issue with these plants and invite disease problems. Space plants at least 18 inches apart. Soil needs to be well drained, yet retain adequate moisture. Consider adding organic matter such as compost to the soil before planting.

Plant care tips

Water regularly but be sure to water the soil rather than the foliage. Add a general-purpose fertilizer when planting or when new growth emerges in spring for existing plants. Regular deadheading will prevent seed production (seedlings rarely resemble the parent plant). Deadheading will also encourage more blooms.

Most phlox will need to be divided every two to four years. The best time to divide is spring, after the plants emerge and are about two to four inches tall; however, you can also divide in the fall. Remember to space divisions at least 18 inches apart; or share them with friends and neighbors.

Problems

The most common problem with these plants is a fungal disease called powdery mildew. It can be destructive to phlox, appearing as disfiguring, powdery white spots on the foliage, sometimes moving to the flowers. Maintaining good air circulation around the plants is critical to preventing this disease. Consider resistant cultivars.

Avoid overhead watering; water in the morning so the plants will have the day to dry out. Be sure the plants are getting as much sun as possible; plants grown in part-shade will be more prone to this problem. If necessary, there are fungicides that can be used.

However, products will not work well once the disease has spread. Consider spraying fungicides as a preventative, before the disease starts or at the earliest sign of infection. Be sure to read any fungicide label completely; ensure phlox and powdery mildew are listed on the label.

Each year the National Garden Bureau selects one perennial as their “Year of” plant; plants are chosen because they’re popular, easy to grow, and adaptable. This year, it’s “The Year of the Phlox,” incorporating many different species of phlox, including the tall garden phlox.

Some of my own favorites include varieties “David” (white), “Bright Eyes” (pink with red centers), “Franz Schubert” (lilac) and “Coral Creme Drop” (deep coral). You can even find varieties with variegated foliage; these can hide a minimal attack of powdery mildew. Visit the National Garden Bureau’s website at ngb.org to get a list of more varieties.

Phlox is a classic American perennial, one of the earliest North American natives to enter cultivation. With the colors and long-lasting blooms, it’s easy to understand what has caught the eye of so many gardeners through the years. Add Phlox to your garden this year!

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