Common Name Garden phlox, tall phlox
Botanical Name Phlox paniculata
Family Polemoniaceae
Plant Type Herbaceous, perennial
Mature Size 2-4 ft. tall, 2-3 ft. wide
Sun Exposure Full sun to partial sun
Soil Type  Moist but well-drained
Soil pH Neutral
Bloom Time Summer
Flower Color Lavender, lilac, pink, purple, salmon, white
Hardiness Zones 4-8 (USDA)
Native Area North America

Garden Phlox Care

Garden phlox is a low-maintenance plant. Here are the main care requirements for growing garden phlox:

  • Choose a location with lots of sun, ideally around six hours or more.
  • Prepare well-draining soil that holds some moisture.
  • Provide garden phlox moderate water, especially in times of drought.
  • In hotter zones, mulch around the plant to keep the roots cool.
  • Fertilize garden phlox lightly each spring.

Planting

Plant garden phlox in moist but well-draining soil in a spot with full sun exposure. Consider tilling the soil and adding compost if necessary.

Dig a hole slightly larger than the root ball, place the plant in the hole, backfill it with soil, then thoroughly water. The best times to plant garden phlox are the spring after the last frost or the early fall.

Light

Grow garden phlox in full sun in northern regions and in partial sun in southern regions.

Soil

Garden phlox does best in fertile, moist soil, with the biggest requirement being good drainage. Well-draining loamy and clay soils work if they include some organic matter. Neutral, acidic, and alkaline soils are all acceptable,

Water

After planting, water thoroughly every few days for about a week or two. Once established, keep the soil evenly moist, but do not overwater.

Avoid overhead watering by pointing the nozzle of your garden hose at an angle to direct the spray to ground level. Keeping the foliage dry will minimize fungal problems.

Temperature and Humidity

Garden phlox does not like hot, humid summers, so it is not a good choice for gardeners in the Deep South. You can mitigate heat and humidity problems by adding mulch to keep the root zone cool.

Fertilizer

This plant wants a soil with moderate fertility. Fertilize garden phlox with compost each year in spring.

Propagating Garden Phlox

Cuttings

Garden phlox can be propagated by taking cuttings. Here are the basic steps:

  1. Use sharp pruning shears to cut a few cuttings about 5 to 6 inches long.
  2. Remove leaves from the lower half of the cuttings.
  3. Plant the cuttings in pots with a well-draining growing medium.
  4. Water the cuttings, and move the pots to a warm location.
  5. Keep the soil moist but not wet until the cuttings root.
  6. Wait until the cuttings are fairly established (about six weeks) before transplanting.

Division

You can also propagate phlox plants by dividing them in the early spring. The process is quite easy:

  1. Dig your phlox plant out of the ground.
  2. Split it into smaller clumps, using a sharp knife.
  3. Replant these clumps, watering them in.

How to Grow Garden Phlox from Seed

You can also direct sow seeds in spring as soon as the ground can be worked. Here’s how:

  1. Sow seeds directly where you want the plants to grow.
  2. Cover them with about 18 inch of soil.
  3. Keep the soil moist until germination, which should occur in five to 10 days.
  4. Thin seedlings so that there is about a foot between each plant.

Potting and Repotting Garden Phlox

If you plan to grow garden phlox in a container, pot it properly to provide the plant with optimal growing conditions. A potting mix is the best soil for a container since it drains well.

Avoid garden soil which compacts in a container, causes poor drainage, and leads to root rot. Garden phlox grown in pots may need staking or some other form of support for its height.

Types of Garden Phlox

Many cultivars of garden phlox have varying flower colors. Some have solid-colored flowers while others are bi-color with a different color in the center.

  • P. paniculata ‘Amethyst Pearl’ has pinkish purple flowers.
  • P. paniculata ‘Bright Eyes’ has pink flowers with magenta centers.
  • P. paniculata ‘David’ has white flowers.
  • P. paniculata ‘David’s Lavender’ has lavender flowers.
  • P. paniculata ‘Delta Snow’ has white flowers with pink centers.
  • P. paniculata ‘Little Boy’ is a dwarf cultivar with purple flowers and white centers.
  • P. paniculata ‘Lord Clayton’ has dark pink, almost red flowers.

How to Get Garden Phlox to Bloom

Bloom Months

Garden phlox blooms in summer, typically in July and August.

What Do Garden Phlox Flowers Look and Smell Like

The flowers bear a mild fragrance and come in a wide range of colors appearing in panicles at the tops of 3- to 4-foot tall stems. They have a slight vanilla scent.

How to Encourage More Blooms

In proper conditions, garden phlox should bloom readily. Make sure your plant is getting enough sunlight to maximize blooms. Deadhead the spent flowers on garden phlox, and regularly weed around your plant so that weeds won’t steal water or nutrients.

Common Pests and Diseases

Garden phlox is susceptible to powdery mildew, a fungal disease that thrives under hot, humid conditions. Some cultivars of garden phlox, such as ‘David,’ are relatively mildew-resistant so look for these cultivars whenever possible.

This perennial may also have issues with aphids, spider mites, thrips, leafhoppers, and phlox plant bugs. You can manage infestations with horticultural oil and insecticidal soap.

FAQ

    • Garden phlox is not an aggressive spreader, but it clumps over time, growing wider, and sometimes spreading via seed.

    • Yes, garden phlox returns annually if it’s in good health in its hardiness zone.

    • Deadhead the spent flowers to encourage the plant to produce new flowers.