Garden phlox

Sun

Full sun to partial shade. Give it afternoon shade in hot districts, but avoid deep shade, which reduces flowering.

Water

Keep the root zone evenly moist, especially during flowering. Water deeply during dry spells; avoid both prolonged drought and waterlogged soil.

Soil

Fertile, humus-rich, well-drained soil. Loam is ideal, but improved clay also suits it; dry, thin soil does not.

Height

2-4 ft (0.6-1.2 m), with some cultivars reaching 5 ft (1.5 m)

Spread

1.5-3 ft (0.45-0.9 m)

Flowers

Summer into early autumn; fragrant flower clusters in white, pink, rose, red, lavender or purple, sometimes with contrasting eyes.

Foliage

Opposite pairs of pointed, lance-shaped green leaves on upright stems; dies back for winter.

Growth

Moderate; forms a substantial clump over several growing seasons.

Care needed

Medium

• Water at soil level during dry spells before the leaves begin to wilt.
• Apply compost in spring; use a balanced fertiliser only if growth is weak or the soil is poor.
• Mulch with 2 in (5 cm) of organic matter, keeping it clear of the emerging shoots.
• Support tall cultivars early with a discreet ring or twiggy stakes.
• Divide crowded clumps every three to four years and replant vigorous outer sections.

Pruning. Remove spent flower heads just above a healthy pair of leaves to encourage smaller repeat blooms and limit seedlings. Cut dead stems to ground level in late autumn or late winter; remove diseased growth promptly rather than leaving it over winter.

Early spring

Plant or divide clumps as new shoots appear, then water thoroughly.

Spring

Apply compost and mulch without burying the crown.

Late spring

Install supports for tall plants before stems lean or lodge.

Summer

Water deeply in dry weather and check leaves for mildew and spider mites.

Summer to early autumn

Deadhead faded clusters unless you want seed.

Late autumn

Remove diseased foliage and cut back dead stems, or leave healthy stems until late winter.

• Plant repeated clumps through the middle or back of a mixed border for a continuous band of summer colour.
• Combine with coneflowers, bee balm and ornamental grasses for a relaxed perennial planting.
• Use pale pink, lavender or white cultivars among roses in a cottage or romantic garden.
• Place fragrant cultivars near a path or seating area where the flowers can be enjoyed at close range.

Garden styles it suits: Cottage garden, English country, Romantic rose garden, New perennial (prairie), Pollinator garden and Sensory garden.

Plant it with: Coneflower, Bee balm, Black-eyed Susan, Switchgrass, Shasta daisy and Hardy geranium.

Wildlife: Flowers provide nectar for butterflies, moths and some bees. Deer and rabbits may browse the shoots and flowers.

• Powdery mildew: choose resistant cultivars, allow good airflow and keep roots evenly moist; remove badly affected foliage.
• Spider mites in hot, dry weather: look for stippled leaves and fine webbing; rinse leaf undersides and use insecticidal soap if necessary, following the label.
• Leaf spots: water at soil level, remove affected leaves and clear infected debris at the end of the season.
• Wilting or scorched lower leaves: check soil moisture and water deeply during drought; if soil is saturated, improve drainage rather than adding more water.

Not known to be toxic to cats, dogs, horses or people. No part is recognised as seriously poisonous, but it is not a food plant and eating it may cause digestive upset.

• Dame's rocket (Hesperis matronalis)

  Dame's rocket has four petals per flower and alternate leaves; garden phlox has five petal lobes and opposite leaves. Dame's rocket also usually flowers earlier.

• Spotted phlox (Phlox maculata)

  Spotted phlox usually has purple-spotted stems and narrower, more cylindrical flower clusters; garden phlox generally has broader, rounded or pyramidal clusters.

Phlox comes from the Greek word for flame, referring to the bright flowers, while paniculata describes its branched flower clusters.

Propagation. Divide established clumps in early spring or early autumn, or take basal cuttings in spring. Seed-grown plants can differ from the parent; divide or take cuttings to preserve a named cultivar.

Accepted botanical name

Phlox paniculata

In the US and Canada

Native in the lower 48 states. Introduced in Canada.

Native range

Alabama, Arkansas, Connecticut, Delaware, District of Columbia, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky and Louisiana.

Measured

Average height 120 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.