How to Grow Phlox
From the Greek phlego, to burn, or phlox, a flame, referring to the bright colours of the flowers (Polemoniaceae). A genus of nearly 70 species of hardy, half-hardy, annual and perennial herbaceous plants all, with one exception, natives of North America and Mexico. Almost all the most important species are from the eastern United States, though the popular annual, P. drummondii, is from Texas and New Mexico. The fine herbaceous plants derived originally from P. paniculata, the garden forms of which may sometimes be listed as P. x decussata, have a most important part to play in the garden as they give colour at a time—July and August—when it very much needs their bright colors. They are extremely easy to grow and all have fragrant flowers. Our rock gardens would be much poorer if they lacked the various forms of either P’ douglasii or P. subulata or their hybrids.
Herbaceous perennial species cultivated
P. carolina, 2 feet, phlox-purple to pink and white, ‘May and June, eastern United States. P. glaberrima, 2 feet, red, May and June, eastern North America in swamps. P. maculata, wild sweet william, 3 feet, violet and purple, summer, eastern North America. These three species are the parents of the early flowering taller phlox. P. paniculata (syn. P. x decussata), 1-4 feet, violet purple, summer, eastern North America.
Alpine species cultivated P. amoena, 6-9 inches, rose, May to June, southeastern United States; var. variegata, leaves variegated with white. P. bifida, sand phlox, prostrate, tufted habit, spiny leaves, flowers pale violet to white, spring, eastern North America. P. divaricata (syn. P. canadensis), 6-15 inches, blue-lavender, May, eastern North America. P. douglasii 4 inches, lilac, May to August, western North America. P. x frondosa, pink, spring, hybrid. P. kelyseyi,6 inches, flowers lilac, spring, eastern North America. P. ovata, 1 foot, rose, summer, eastern North America. P. pilosa, 10-20 inches, purplish-rose, summer, eastern North America. P. x procumbens, 6 inches, lilac-blue, June, a hybrid. P. stellaria, 6 inches, pale blue, April to May, hybrid. P. stolonifera (syn. P. reptans), 6-12 inches, stoloniferous habit, flowers violet to lavender, 1 inch across, April to May, eastern North America. P. subulata, moss phlox, 6 inches, purple or white, eastern United States.
Border cultivars P. paniculata is the border perennial phlox which has given rise to many good plants, flowering from July to October, sweet smelling, and very colourful. ‘Antoine Mercie’, deep mauve with white centre; ‘Border Gem’, deep violet; `Brigadier’, orange-red; ‘Europe’, white with red centre; ‘Frau Antonin Buchner’, white; ‘Jules Sandeau’, pure pink; ‘Le Mandi’, rich purple; ‘Leo Schlageter’, dark red; `Lofna’, rose-pink; `Mrs A. Jeans’, silvery-pink; `Rijnstroon’, rose-pink; `Starfine’, red; ‘Thor’, salmon-red, Many more will be found in nurserymen’s lists.
Alpine cultivars P. douglasii, ‘Boothman’s Variety’, clear mauve; ‘Eva’, pink with deeper centres; ‘May Snow’, white; `Rose Queen’, silvery pink; ‘Snow Queen’, white; ‘Supreme’, lavender-blue. P. kelseyi, ‘Rosette’, stemless pink flowers. P. stolonifera ‘Blue Ridge’, soft blue. P. subulata `Appleblossom’, pink; `Benita’, lavender-blue; ‘Brilliant’, bright rose; `Camla.:, clear pink; ‘Fairy’, mauve; ‘G. F. Wilson’, mid-blue; ‘Model’, rose; ‘Pink Chintz’, pink; ‘Sensation’, rose-red; `Temiseaming’, magenta-red; ‘The Bride’, white.
Cultivation The tall herbaceous phloxes need a moist loam, preferably on the heavy side. They do perfectly well on chalky soils, provided these are enriched. Though in the past shady positions have been given to phloxes and this does not actually kill them, they do better in sunny positions. Plant from October to March, and feed generously thereafter with manure or compost and inorganic fertilizers, as they are greedy feeders. Lift, divide and replant every three years. They are readily raised from root cuttings and this has the advantage of providing plants free from the stem eelworm, by which the herbaceous phlox are all too often attacked.
Alpine phlox species also like a rich soil, and a sunny ledge on the rock garden or on top of a wall. Many of them may be easily increased by layering, or they may be divided into separate plants each possessing roots, and this is best done in March. A few of the more dwarf or less vigorous kinds may be given alpine house treatment. Winter wet is their bane.
Eelworm attack on phlox, by the eel-worm species Ditylenchus dipsaci, causes bloated and wrinkled foliage, stunted, swollen and split stems and whiptail shoots. The same strain of eelworm will attack gypsophila, oenothera, gladiolus, potato, aubrieta, as well as a number of weeds such as mayweed and shepherd’s purse. Hot water treatment of the dormant stools for one hour at a temperature of 110°F (43°C) controls the pest. The plants must be put back in the uncontaminated soil and infected areas should be kept free of susceptible plants and weeds for at least three years. It is possible to propagate infested phlox without transmitting eelworm by means of seed or by true root cuttings.