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.
- Shelf Life: Plant in the garden when night temperatures stay above 45°F.
- Plant Preparation: Cut away any yellow or brown leaves or broken stems. This grooming is completely normal and will continue to take place as the plant grows.
- Potted Plants: Rather than moving lavender to the garden, you can re-pot into large containers. Re-pot the plants separately into 8" pots, or together inside one larger container.
- Soil: If your soil is clayish, amend it with a standard garden soil for adequate drainage.
- Garden Location: Pick a sunny location. Borders, perimeters, and walkways are a great location.
- Planting Depth & Spacing: Plant separately, spacing about 20"-24". Dig holes twice the width of the root ball and about 5"-6" deep. Place them in their holes. Cover with an inch or two of soil and pack soil firmly around root.
- Plant Height: Most will grow about 24"- 28" tall.
- Sprouting Time: Phlox sprouts in May. It will take a little longer if the temperatures are still cool.
- Watering: Water thoroughly upon planting and keep moist thereafter.
- Fertilizer: This helps maintain flower size and count from year to year. For best results, use plant booster once a month all summer long.
- Lighting: Full to partial sun is preferred. Dappled sun is fine too.
- Blooming: These plants will bloom mid-summer through autumn yearly.
- Temperature Zones 4-9: These are hardy down to a -30°F.
- Winter Dormancy: After the first heavy frost, cut all shoots back to about 3" above the soil. Plants rest from November to May.
- Propagating: These plants will re-bloom and spread every year. They can be subdivided in early spring or autumn after 2-3 years.
- Cut Flowers: These make wonderful flowers for your cut flower garden.
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!