As plants go, phlox is a truly American plant. To begin with, all the 50+ or so accredited species hail from this continent. The lone dissenter is from Siberia.
Phlox belongs in the Polemoniaccae family, which means “flame.” The flowers are generally borne in panicles, cymoses, clusters, trusses, or heads, with rounded individual blooms, sometimes garnished with “eyes.”
Subtle fragrances are found in some species, and there is a sparkling race of annual kinds. Since the blossom time of phlox extends from early spring to numbing frosts, let us follow the seasons.
Blue Phlox With Daffodils
The blue heads of the spring phlox or wild sweet William (Phlox divaricata) usher in the spring along with daffodils, primroses, and other favorites. Woodlanders prefer partial shade and summer moisture and will colonize as a ground cover under good conditions. Yet this habit need not rule out its use in rock garden borders since the basal shoots are not unduly aggressive. An elusive aroma reminds one faintly of the gold-band lily. Cut the flowering stems back after flowering. Plants grow 12″ to 15″ inches tall.
Forms of this showy species are worth growing. Phlox divaricata canadensis, a compact grower, has notched blue petals. Phlox divaricata laphami, a western native (sadly jumbled in the trade), is a lovely periwinkle blue with neatly rounded petals. Finally, Phlox divaricata alba is a delightful white.
Mentioned mainly for the record is Phlox arendsi, a hybrid between Phlox divaricata and the showy summer phlox (Phlox paniculata). Generally impure colorings and a propensity toward powdery mildew outweigh its commendable habit of a long blooming season.
Phlox stolonifera resembles the spring phlox at a cursory glance, but this species, native of Ohio and Pennsylvania to Georgia, is a spectacular ground cover when in flower. Showy little trusses, usually purple or violet, are held only six inches above the creeping basal shoots. Let it roam naturally as a matting plant in light shade.
The moss or ground phlox (Phlox subulata) is a real spring tonic to all if not used too lavishly, especially the undesirable magenta form. Native from New York to Michigan and extending to North Carolina, it approaches gypsy status in Pennsylvania. Everyone knows its prickly, narrow-needled leaves, often evergreen, on broad cushions, perhaps two feet across.
It is an unforgettable sight in May when it blooms abundantly in rock gardens on walls or as edgings, doing best in sunny, porous soil. An early summer shearing, a light top dressing with compost, and occasional division of large mats will keep it thriving. Fall reblooming sometimes occurs, a habit found in many introductions by the hybridizer, J. Herbert Alexander.
Trailing and Moss Phlox
Many gardeners confuse the trailing phlox (Phlox nivalis) and the moss phlox, but several differences present themselves.
Trailing phlox has a looser habit of growth, blooms later, and has longer leaves. The habit of sporadic fall bloom occurs in hybrids crossed with moss phlox, and its gold-tipped stamens are hidden well down in the petals. Indigenous to the south, it is often tender in open northern winters, regrettably so because of its large huge blossoms. If possible, grow it in poor, sandy soil in the fall sun to harden it for winter.
NOTE: The sand phlox (Phlox bifida) is considered a poor imitation of the moss phlox by some plantsmen.
Phlox For Dry Places
Yet the more restrained tufts of leaves are less prickly, and shadings confine themselves largely to light purple, bluish, or white. Nothing is more durable in dry spots, and a cobwebby effect replaces the dense habit of the moss pink. First named in Indiana in 1826, it is found in light soil reaching Arkansas and Tennessee and is an obvious possibility for extensive breeding.
The result of crossing trailing and sand phlox gave us Phlox henryae, which blooms effectively in hot, arid areas. The sizable pale phlox pink blooms, but blue and lavender forms have also been cultivated.
A prostrate, sprawling species of the Pacific Coast mountains is Phlox diffusa, completely at home in poor soil or sunny rock ridges. The lavender, pink or white flowers may appear again in late summer. Also alpine, but worthy of trial in eastern settings, are Phlox hoodi and Phlox scleranthifolia. Spotless white blossoms cap both.
Phlox amoena furnishes vivid splashes of rosy pink well into summer on neat, slender-leaved piles of green foliage, less than 12″ inches tall. However, this doughty Spartan from dry southland wastes invariably succumbs under richer diets. Moreover, we find Phlox procumbens offered as Phlox amoena.
Phlox procumbens is derived from moss phlox Phlox stolonifera and will even flourish in partial shade. In May and June, the trim mounds of slimly ovate foliage erupt in bright rosy-purple clusters.
Phlox douglasi from Washington is extremely popular in England but is less accommodating here. Very sharp drainage is essential, and the flower color variations, from pale mauve to magenta and white, may not always please. Yet, the rounded blossoms congregate generously on stiff branches under 10″ inches of stature. Phlox caespitosa is not markedly different but ordinarily bears blooms of lilac tints only.
Phlox Ovata Pulchra
Lovely indeed is the periwinkle phlox (Phlox adsurgens) if given the acid soil and partial shade it relishes. This may also be true of other so-called malcontents from western mountains. Shining leaves, perhaps bronzed in winter, form attractive mats studded with six-inch heads of inch-wide pale pink or salmon flowers. Demure white centers add a pleasing contrast.
Roaming as far north as Connecticut, Phlox pilosa is a distinctly eastern species, which naturalizes itself in dry, sandy stretches. Purplish-rose trusses frequently top the 12″ to 18″ inch stems but curious variations also appear. Incidentally, hybrids in nature with spring phlox are not unknown, despite the latter’s preference for a higher range.
The mountain phlox (Phlox ovata), with glistening, oval leaves, thrives in fairly heavy soils in sunny or somewhat shaded exposures. In June, the tightly packed clusters on nine to 18″ inch stems appear in purple, deep pink, or light red hues. It needs dividing occasionally in late summer and usually holds up in bouquets.
Phlox ovata pulchra, a 1929 discovery from Alabama, is justifiably dubbed pastel mountain phlox. Large, shapely heads of heavenly pink simply defy adequate description. However, we have found that light shade, peaty moist, well-drained soil, and dividing every two years are needed for optimum results.
Smooth phlox (Phlox glaberrima) is so-called by dint of its natty, deep green foliage, yellowish in the young stages. The narrowly ovate leaves are adequately spaced on glossy red stems, carrying dome-like clusters of purplish rose or white in early summer. It roams widely over our mid-west and upper southlands in moist meadows or open woods, reaching 18″ to 24″ inches tall.
Unorthodox stems, spotted as if dusted with paprika, identify the mountain phlox (Phlox maculata). Narrow leaves, closely tiered, and tight pyramidal panicles, mainly in a gaudy carmine hue, arc its characteristics. Happy only when the sunny, moist conditions of its extensive range arc duplicated, it dislikes drought and impoverished soils. It can tower to a lanky five feet, but half that height is more customary.
The species Phlox suffruticosa, native from Ohio south, became popular in France and England last century when it was hybridized widely. European catalogs listed up to 20 different varieties. Yet, nearly all are in the magenta range, devoid of clear color, save Miss Lingard, a superb white.
Miss Lingard is still unsurpassed with its long, classically tapering cones of starchy white, sometimes flushed with pink. It often flowers in Connecticut about Memorial Day. After weeks of bloom, the gleaming leaves catch the eye, and blooms often re-appear in late summer. Of considerable value as a cut flower, the reddish stems may stretch to three feet. Divide clumps about every three to four years. Given a tidy moist soil, in light shade or full sunlight, it will endure for years.
Annual or drummond phlox (Phlox drummondi), a perky annual, was first sent to Glasgow from Texas in about 1835. Today its blooms have been glamorized into a perpetual rainbow of color for summer gardens. Herein lies the only yellow of the genus, a timid primrose shade. The form Phlox drummondi nana compacta produces its blooms on six-inch plants.
The Tall Garden Phlox The Best of Them All
The early flowering phlox can hardly compare with the lavish color of the tall garden phlox (Phlox paniculata). Their vigor, the huge tresses of striking hues, and the late June to September pyrotechnics of this group can highlight an entire border. Each waving stalk, to three feet or more in height, is a virtual bouquet in itself. European breeders have featured the subtle fragrance. Summer phlox in nature grows from New York to Georgia and Arkansas, shabbily arrayed in color alongside the modern hybrids of this notable species.
Sad to relate, misguided amateurs more poorly treat few flowers. From sheer neglect, gaunt beanstalks, nearly empty of clean foliage, are customarily found capped by runty florets. Why should such a tattered appearance symbolize problem patches “where once the garden grew?”
The rich soil of liberal organic content is desired, as is frequent watering in prolonged droughts and occasional spraying or dusting. Overcrowding leads only to diseased foliage caused by poor air circulation. Two feet of “elbow” room is essential for each clump. Division about each fourth year prevents deterioration of flower size and general health.
Snip old floral heads as they fade, to encourage branching and later bloom display, and there will be no volunteer seedlings of disturbing magenta. Sunlight is favored, but light shade during the day’s most scorching hours does no harm.
In general, varieties of the moment seem preferable to older favorites, with their increased blossom size, subtle tintings, and more compact habit.
Here, then, is a hasty resume of the latent promise in the animated phlox for gardens. It should be stressed, too, that practically all may be safely transplanted in bloom with a ball of soil.
HC-0856 by C Roderick