Most Phlox are American natives so they are easy to grow in average soil. They all have a show of flowers that lasts for weeks.
Tall, perennial, garden phlox, blooms in the heat of the summer and into the fall. Creeping and native phlox bloom in the spring.
Early varieties were susceptible to powdery mildew, a fungal disease (Erysiphe cichoracearum), that turns the leaves a grey-green color, but new hybrids have eliminated that problem.
Some of the new varieties are Phlox paniculata Little Boy, Phlox paniculata Laura and Phlox paniculata Purple Flame.
Little Boy is short and has lilac blue flowers with a white center. Grows 20-inches tall and wide. Laura is lavender with a white eye in the center. Long blooming, grows 30-inches tall and two feet wide. Purple Flame is a 12-inch tall dwarf that blooms into September. Spreads to two-feet wide.
What is commonly called Thrift or Moss pink is the groundcover Phlox subulata. This variety grows in well-draining soil so it is perfect for spring color in rock gardens and other hot, dry spots. About 4-inches tall and 2-feet wide. Colors: White, pink, rose, lavender and blue.
The annual, seed grown, Texas native Phlox Drummondii, blooms in white, cream, pinks, lilac, rose, purple, reds, and almost black. Some have a contrasting eye color. The tall varieties include Finest and Fordhook Finest. Dwarfs include Beauty, Globe, Petticoat and Twinkle. Flowers last until frost.
Oklahoma native phlox include Woodland Phlox, Phlox divaricata, or Sweet William Phlox. It grows to about one-and-one-half feet tall under deciduous trees in the shade. The fragrant, blue flowers bloom in the spring, with a bloom time that lasts over a month. Plant on and around spring blooming bulbs, in rock gardens. Shop for these varieties: Arrowhead, Dirigo Ice, Fuller’s White and London Grove.
Prairie Phlox, Phlox pilosa, forms a low growing clump. Prairie is a mildew-free variety with blue to pink, long lasting flowers. Look for Chattahoochee, Mood Blue, Eco Happy Traveler and Ozarkana.
The best way to prevent powdery mildew is by removing and destroying the stalks and leaves of your plants in the fall. That measure will help slow the arrival of the disease next summer.
In one study of phlox, the least disease prone were: David, Windsor, Alpha, Blue Boy, Prime Minister, Orange Perfection, Starfire, H.B. May, Fairest One, Bright Eyes, Dorffrendl, Dodo Hanbury Forbes, Eva Cullum, Franz Schubert and Fairy's Petticoat.
The most disease prone were: Sternhimmel, Adonis, Mt. Fuji, White Admiral, Mrs. R. P. Struthers, Pinafore, New Bird, Dresden China and Anja.
If you grow heirloom phlox, check the bottom leaves and at the first sign of mildew, spray with a fungicide. Another precaution is to divide them every two or three years so air can circulate throughout the clump.
To divide a tall garden phlox, dig up the entire plant in the fall or spring. Discard the center roots and stems and cut the outer shoots into new, small plants and re-plant them in prepared soil at least a foot apart.
Garden centers have summer phlox in stock now so you can see the colors. Perennial Pleasures Nursery in Connecticut offers 128 varieties (perennialpleasures.net) and native phlox is available from Wild Things at wildthingsnursery.com.
Park Seed and Thompson Morgan have annual Phlox drummondii seeds. They germinate in a week at 62-degrees. HPS Seed offers a mix of perennial Phlox paniculata for fall planting. Prairie Moon (prairiemoon.com) has seeds for P. paniculata, P. maculate and P. pilosa.
All the perennial varieties can be propagated from fall stem cuttings and root division.
Phlox has scented flowers that attract hummingbirds, skippers, moths and butterflies. There are varieties for every garden.