Phlox (paniculata) is commonly referred to as garden phlox. Not to be confused with annual phlox or creeping phlox, it's an herbaceous perennial plant with simple leaves on slender green stems. The flowers are white, pink, red, or purple, blooming in the summer through fall.
Height & Spread
Depending on the variety, phlox plants increase in size from 8" – 20" or more. There are dwarf varieties that grow to only 8". Some phlox grow in low mounds, whereas others spread.
Phlox blooms all summer, from June until frost. Individual 1" wide flowers are made up of five petals and have a flat star-shaped appearance. They grow in tight clusters atop erect stems. Flower colors include white, pink, salmon, yellow, purple, and mixed. Some have "eyes" of contrasting colors. Others have fringed petals. While they attract butterflies with their vivid colors, they have no fragrance.
The leaves of phlox are 1" – 3" long, smooth, and light green. They're narrowly oval to lance-shaped with pointed ends. The lower leaves on each stem grow individually at different heights on the stem, while the upper leaves near the flowers grow in pairs opposite each other on the stem.
Frequently Asked Questions
Q: What is the white powder on the leaves?
A: Powdery mildew is caused by fungi that live on the surface cells of a plant, coating infected leaves with a white or ash-gray powdery mold. Badly infected lower leaves become discolored and distorted, then drop off. It's the most common disease in phlox. The disease is encouraged by crowding and warm, humid weather. It's unsightly, but rarely kills phlox. Spray healthy plant foliage thoroughly with sulfur every two weeks, starting as soon as the whitish coating of the fungus appears to control its spread. Read and follow the instructions on the product label. Allow ample spacing between plants for good air circulation and avoid wetting foliage when watering. Collect and discard all above-ground debris in the fall.
Q: Is deadheading a good idea?
A: Deadheading is not necessary, but will encourage phlox to re-bloom quite heavily in the fall. Remove spent flowers to maintain a neater appearance and extend flowering time.
Q: Can I subdivide phlox?
A: Yes. They can be subdivided in early spring when the new growth begins to occur. Do so after 2 – 3 years as this will increase the yield considerably.
Q: Can garden phlox grow in rocky soil?
A: Garden phlox are not recommended for rock gardens. If your soil is rocky, amend it with compost or organic material.
Q: Is phlox deer-resistant?
A: Yes, but it's a favorite of butterflies!