How To Grow and Care For The Hardy Phlox Garden Perennial

Phlox paniculata (FLOKS pan-ik-yoo-LAY-tah) is a perennial flowering member of the Polemoniaceae (po-le-moh-nee-AY-see-ee) family of plants. 

Its native territory is the Eastern United States, which grows naturally throughout New York state, Iowa, Mississippi, Georgia, and Arkansas. It has also naturalized in many other conducive locations.


The plant is commonly referred to by the following common names:

  • Cross-Leaved Phlox
  • Summer Phlox
  • Perennial Phlox
  • Autumn Phlox
  • Garden Phlox
  • Fall Phlox
  • Tall Phlox

The plant’s genus name, Phlox, is Greek for “flame.” The specific epithet, paniculata, refers to the panicles of beautiful flowers this plant produces. 

Hardy Phlox Care

Size and Growth

This herbaceous perennial plant has an erect growth habit, reaching 2′ to 4′ feet in height and 2′ to 3′ feet wide.

Cross-Leaved Phlox aromatic leaves have been used in folk medicine as a treatment for boils and as a laxative. The plants’ deep green leaves may be up to six inches long. They are deeply veined and may be oval, elliptical, or lance-shaped.

Flowering and Fragrance

Summer Phlox produces panicles of fragrant, showy, colorful blooms throughout the late summer and into the autumn months in shades of:

  • Variegated
  • Lavender
  • Burgundy
  • Purple
  • White
  • Blue
  • Pink
  • Red 

The flower colors may vary depending on the varieties of phlox.

Light and Temperature

Autumn Phlox can grow in partial shade but does better in full sun. However, it doesn’t like hot, humid summers.

It can also tolerate light shade, but too much shade may hinder flower production.

This native plant is winter hardy in USDA hardiness zones 4a-8b.

Watering and Feeding

Keep Phlox well-watered throughout the summer months to ensure moist soil. Ideally, provide an inch of water per week during the growing season.

In addition, provide a layer of organic mulch to help retain moisture and keep the plant’s roots cool.

Moreover, provide your Phlox with plenty of compost mixed into the garden soil and as a mulch for ample beautiful blooms. If you wish, you can provide feeding of a balanced (10-10-10) fertilizer early in the springtime and again after the first flush of flowers has faded.

Soil and Transplanting

Summer Phlox will thrive in light, well-drained soil. However, this plant will also do well in fertile loamy soil well-amended with organic matter. The plant prefers neutral soil (6.0 – 8.0) but may tolerate slightly acidic soil.

It’s best to plant phlox in autumn or spring while the soil is moist and warm and after the danger of frost has passed.

Moreover, ensure adequate space between plants (1′ to 3′ feet) because good air circulation is essential in keeping these plants free of fungal infections.

Grooming and Maintenance

Deadhead flowers regularly to help extend the blooming season. Pinching the stems back in late spring also helps increase branching.

If you want bushier plants and more flower heads, cut the stems or pinch back the growing tips in early summer.

Very tall plants may need to be staked. And just before wintertime, cut or mow your Phlox to the ground. Rake away and dispose of the felled plants. This will help control the development of powdery mildew.

In addition, add a layer of mulch to keep the roots moist and conserve soil moisture in colder regions. Cutting the foliage right after the first frost spells is also recommended.

How To Propagate Hardy Phlox

If you are planting purchased Phlox seeds, follow the packaging directions carefully.

In a conducive environment, Phlox self-seeds easily; however, the resulting plants will not be like their parents if you have planted a specifically developed cultivar.

If you want more of your existing Phlox plants, use stem or root cuttings or divisions from the parent plant.

Phlox – Propagate From Cuttings

Hardy Phlox Pest or Diseases

Perennial Phlox tends to harbor pests and also has a significant number of problems with fungal diseases. Powdery mildew is the biggest offender, especially in wet, humid weather.

The best solution is to remove and destroy diseased plants.

In addition, ensure not to overwater your plants, avoid overhead watering and provide ample air circulation to help prevent this problem.

Pests, such as spider mites, phlox thrips, and thrips, can be problematic. Good care, regular inspection, and insecticidal soap or organic Neem oil pesticide treatment should keep them at bay.

Is the plant considered toxic or poisonous to people, kids, and pets?

This pretty native plant is non-toxic and safe to grow around kids, pets, and livestock.

Is the plant considered invasive?

Although Phlox is easy to naturalize in a conducive setting, it does not tend to take over or push out native plants. Even so, it’s a good idea to keep an eye on its spread and curtail it as needed in areas where the plant is not native.

Suggested Hardy Phlox Uses

Birds, hummingbirds, butterflies, bees, and other variety of pollinators are very attracted to Garden Phlox flowers, so the plant is a good choice for a pollinator, butterfly, bird, wildlife, or rock garden.

The tall, attractive plants make a pretty backdrop for lower-growing and shorter plants. They are also useful for bordering flower beds, herb gardens, flower gardens, or lining paths and walkways due to their masses of flowers.

In addition, Garden phlox are versatile plants that make a great ground cover with their fragrant flowers. Garden phlox’s pink, purple, or white flowers and sturdy stems also make excellent cut flowers.

Moreover, their flower clusters also make a great addition to summer bouquets.

Phlox naturalizes easily and makes a beautiful addition to a woodland setting. Woodland phlox grow happily under black walnut trees.

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