Fabulous phlox

Their telltale magenta flowers enliven native landscapes for many weeks from summer to fall, while a myriad of cultivars in a rainbow of colors grace gardens everywhere. They owe their prodigious nature as much to the oversized flower trusses that crown tall stems as to the vivid pinks, purples, reds, and oranges of the flowers.

Phlox paniculata, garden or summer phlox, is one of 60 or so species of phlox native to North America. P. paniculata is native to the eastern United States, from New York to Georgia, and west to Illinois and Arkansas. It has been in cultivation in Europe since the 1800s and many of the early cultivars originated in England and Germany.

Phlox maculata, early or meadow phlox, is a native of the eastern United States, too. While similar in habit to garden phlox, its flowers are borne in elongated cylindrical clusters earlier in the summer. The species name reflects its purple-maculated or spotted stems. Phlox × arendsii, a hybrid between P. divaricata (blue phlox) and P. paniculata, boasts greater mildew resistance than garden phlox. P. paniculata, P. maculata and P. × arendsii are collectively referred to as border phlox.

Flowers are without a doubt the main ornamental attribute of the border phlox. A pavonine palette of flower colors is available including shades of pink, salmon, orange, red, purple, lavender, blue and white. While the magenta-pink flowers of wild P. paniculata are unmistakable, modern cultivars offer a variety of distinctive colors such as voluptuous cherry red (‘Miss Mary’), whimsical pink and white (‘Peppermint Twist’) and delicate pink and yellow (‘Sherbet Cocktail’). Flower size varies from ½-inch to almost 2 inches wide, whereas the panicles typically range from 4-6-inches tall and 6-8-inches wide. Flowers are fragrant, although the degree of fragrance is variable among cultivars.

Evaluations
From 2001 through 2009, the Chicago Botanic Garden (USDA Hardiness Zone 5b) evaluated 78 Phlox taxa in full-sun trials. The study concentrated on cultivars of P. paniculata but included P. × arendsii cultivars and unspecified hybrid cultivars.

Plants were regularly observed for descriptive traits such as flower color, bloom period, foliage color and plant habit. Data also was collected on disease and pest problems, winter injury and habit quality and plant health issues related to and/or affected by cultural and environmental conditions.

While 27 phlox received high ratings for outstanding flower production, good health, and strong habits, only P. paniculata ‘Shortwood’ received a five-star excellent rating for its exceptional overall performance and superior resistance to powdery mildew and spider mites. Rosy-pink ‘Shortwood’ is a chance seedling of white-flowered ‘David,’ discovered by Sinclair Adam in Pennsylvania and named for the garden of Stephanie Cohen, perennial plant expert and garden writer. At 50 inches tall, ‘Shortwood’ is anything but short. In fact, with its large size and vivid flower color, somewhat of a throwback to the species, ‘Shortwood’ defies the recent trend in phlox introductions. But its noteworthy resistance to powdery mildew sets ‘Shortwood’ apart. 

Other border phlox that fared well were P. maculata ‘Flower Power,’ P. paniculata ‘Bartwelve,’ P. paniculata ‘Frosted Elegance,’ P. paniculata ‘Lichtspel’ and P. paniculata ‘Peppermint Twist.’

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 Photo courtesy of www.northscaping.com