Phlox Growing Guide: How to Plant and Care for Phlox

Phlox is a group of perennial and annual plants in the Polemoniaceae family that grow panicles, or branching flower clusters. Found across North America, these fragrant flowers grow in star-shaped blooms. Phlox’s vibrant flowers attract hummingbirds and butterflies, making the plant fit for pollinator gardens.

With more than 67 species, phlox come in a variety of sizes and colors. Common phlox flower colors include lavender, pink, orange, white, and red. Phlox also have bicolor blooms, which have an “eye” in the center of each flower, or a color shade distinct from the outer petals.

Phlox is a hardy plant with a long flowering season. The bloom time varies depending on the type of phlox. For example, creeping phlox blooms from early spring through early summer, while garden phlox blooms from late summer through early fall.

Phlox belong to two main categories: low-growing phlox and tall-growing phlox. Low-growing phlox grow in short, thick mounds and often resemble a carpet of color spreading across the ground. Tall-growing phlox grow upward instead of outward, reaching as high as three to four feet.

1. 1. Woodland phlox (Phlox divaricata): This phlox blooms lavender, dark purple, white, or blue flowers in early spring. This variety of phlox prefers partial shade and moist soil.
2. 2. Creeping phlox (Phlox subulata): Also known as moss phlox or moss pink phlox, this low-growing phlox is often used as ground cover for rock gardens with thick colorful blooms. ‘Candy Stripe’ is a creeping phlox cultivar with white-and-pink flowers. Creeping phlox prefer full sun exposure and well-drained soil.
3. 3. Garden phlox (Phlox paniculata): Also known as summer phlox, this deer-resistant variety of phlox produces tight bundles of flowers that grow between three and five feet tall. While garden phlox is susceptible to powdery mildew, cultivars ‘David’ and ‘Jeana’ are mildew-resistant.
4. 4. ‘Laura’ (Phlox paniculata ‘Laura’): This tall garden phlox has magenta petals dotted with a white center. With partial-full sun, ‘Laura’ can grow between three and four feet tall.
5. 5. ‘Violetta Gloriosa’ (Phlox paniculata ‘Violetta Gloriossa’): A tall-growing phlox with a lilac color. For these purple flowers to bloom, this type of phlox needs full sun and moist soil.

Though generally hardy, you should review your phlox type to learn about its planting preferences.

• Choose a planting site: Most phlox grow best in partial or full sun and moist soil. Find a spot that receives sun for most of the day and has good drainage to prevent water from building up at the roots and causing mildew.
• Prepare the site: Loosen the soil, removing any weeds or rocks in the process, before mixing in a two-inch layer of compost to provide nutrients to the soil. Dig holes about twice as wide as your phlox. The spacing of your phlox depends on the type of phlox you’re planting. For example, creeping phlox only need two feet of distance, while garden phlox require about 18 inches of space. Separating your plants provides phlox with air circulation, which prevents mildew.
• Plant your phlox: Before placing your phlox plant in the ground, gently pull the roots outward to loosen them. This helps the roots branch out in the soil. Using two hands, place your phlox in the hole. Once planted, cover the bare roots with soil, so they’re no longer visible.

While phlox are hardy, long-blooming flowers that require minimal maintenance once planted, they still need attention. Below are some tips you can follow to keep your vibrant phlox growing strong throughout the bloom season:

• Water the base: Water the root zone, or base of the plant, which allows the water to drain evenly and prevents the leaves from getting wet. Wet leaves can grow mildew, so be sure to aim your watering can or hose low. Watering your phlox in the morning is another way to prevent mildew, as this helps your plants dry in the sun.
• Keep the soil fertile and moist: Phlox grows best in slightly alkaline and moist soil. You can add a few drops of lime juice to lower the soil’s acidity level. To keep your soil moist, add a two-inch layer of mulch. This also helps prevent weeds from growing. Finally, add a thin layer of compost to the soil, which provides nutrients that stimulate growth.
• Deadhead flowers and leaves: During the bloom season, deadheading your phlox helps the plant rebloom. Cut dead flowers and leaves. After your phlox naturally dies at the end of the bloom season, cut back the stems to prepare the phlox for winter.

Protecting your phlox from different pests and ailments can keep your phlox blooming from late spring to early fall. Common pests and diseases include:

• Powdery mildew: This common fungal disease results from a lack of sunlight and poor air circulation. The first sign of powdery mildew is white spots on the top of leaves. As the mildew continues to spread, infected leaves can turn yellow and twist. Good air circulation and sunlight prevent powdery mildew. To treat powdery mildew, spray a fungicide containing sulfur on your phlox. This also works as a preventive measure against powdery mildew.
• Nutrient deficiencies: Lack of water, sunlight, or soil nutrients can cause nutrient deficiencies in your phlox. Yellow leaves commonly signify nutrient deficiency. Watering your phlox during drier months and adding compost to the soil can help prevent nutrient deficiencies in phlox.
• Spider mites: These tiny animals feed on the underside of phlox leaves, coating them with small webs. Over time, leaves infested with spider mites turn yellow and develop brown spots. Spraying water on your phlox leaves removes spider mites; however, let the leaves dry to avoid mildew growth.
• Phlox bugs: Phlox bugs (Lopidea davisi), a red-and-black insect, feeds on phlox leaves, stems, and flowers. Signs of phlox bugs include yellow or light green spots on leaves and curling brown leaves. Routinely check your phlox leaves for these bugs. If you spot phlox bugs or signs of phlox bugs, apply insecticidal soap to both sides of the leaf.
  

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