Why does my phlox get white spots?

That is likely powdery mildew, which thrives when the leaves stay wet or air flow is limited.

Should I deadhead my phlox?

Yes, deadheading can encourage a second flush of blooms later in the season.

Plant guide

Garden Phlox.

Phlox paniculata

Pronounced floks pan-ik-yoo-LAY-tuh

Also known as Fall Phlox, Fall-pink, Garden Phlox, Panicled Phlox, Perennial Phlox, Perennial-pink, Phlox, Summer Phlox

Garden Phlox is a classic perennial that brings height and fragrance to the summer border. It produces large, showy clusters of flowers that attract butterflies and hummingbirds. These plants are beloved for their long bloom time and reliable performance in sunny garden beds.

At a glance

Care level: Moderate
Plant type: Herbaceous perennial
Light: Full sun to partial shade
Indoor light: bright-indirect
Water: Every 3 to 7 days
Mature size: 120 cm tall by 90 cm wide
Growth rate: medium
Hardiness: USDA 4 to 8
Bloom time: Mid to late summer

Care

Provide consistent moisture and good air circulation to prevent powdery mildew on the foliage. Deadhead spent blooms to encourage a second flush of flowers later in the season. Watch for signs of fungal issues during humid weather and thin out stems if the plant becomes too crowded.

Watering: Keep the soil consistently moist but not waterlogged.
Feeding: Apply a balanced liquid fertilizer during the active growing season.
Pruning: Cut back stems to the ground in late autumn after the foliage dies.
Repotting: Divide clumps every few years to maintain plant vigor.
Soil: Rich, moist, well-draining soil
Soil pH: Neutral to slightly acidic
Temperature: -34 to 30°C
Humidity: 40 to 60%
Drought tolerance: moderate
Lifespan: Perennial, typically 5 to 10 years.
Fragrance: strong
Deer and rabbits: low

Signs it needs repotting

Roots growing out of the drainage holes.
Water sitting on the surface of the soil for too long.
The plant stops growing even during the active season.

Safety

People: This plant is generally considered non toxic to humans.
Pets: This plant is generally considered non-toxic to cats and dogs.
Children: The stems and leaves are not poisonous, but they are not meant to be eaten by small children.
Contact allergens: Some people may experience mild skin irritation from handling the foliage.
Airborne allergens: The pollen is not typically a major trigger for hay fever.
Edibility: While the flowers are technically edible, they are often treated with pesticides in nurseries, so please do not eat them unless you know they are grown organically.

How to identify it

Tall upright stems
Opposite lance shaped leaves
Large terminal flower panicles
Fragrant tubular blooms
Five petaled flowers

Height: 0.6 to 1.2m
Spread: 0.45 to 0.9m
Leaves: green, deciduous
Flowers: pink, purple, white, red, 2 to 4cm

Common problems

Powdery mildew — A white fungal growth on the leaves often caused by poor air circulation or humidity.

Growing it

Propagation: division, cuttings, seed
When to plant: spring, autumn
Overwintering: Cut the stems back to the ground after the first hard frost to prevent disease overwintering. Apply a light layer of mulch if you live in a very cold climate.
In containers: It can grow in large pots, but ensure the container is at least 12 inches wide to accommodate the root system.

Division

Dig up the clump in early spring or fall.
Use a sharp spade to divide the root ball into smaller sections.
Replant the divisions at the same depth they were previously growing.

Plant your phlox with shorter perennials in front to hide the lower stems which can sometimes look a bit bare.

Grows well with

Purple Coneflower — They share similar light and moisture needs while providing a nice color contrast.
Daylily — Daylilies provide a different texture that complements the tall stems of the phlox.

Keep away from

Similar species

Creeping Phlox — It is a much lower growing, mat forming relative used as a groundcover.

Science

Family: Polemoniaceae
Genus: Phlox
Order: Ericales
Class: Magnoliopsida
Native range: Eastern and central North America.
Conservation: This species is common and not of conservation concern.

It naturally grows in moist, fertile woods and meadows where it can spread through underground rhizomes.

Value to wildlife: nectar source
Pollinators: bees, butterflies, moths, hummingbirds
Uses: cottage garden borders, cut flower arrangements, pollinator gardens

Through the year

JFMAMJJASOND

Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 7/9
Temperature: 5/9
Moisture: 6/9
Nutrients: 7/9

Taxonomy resolved against GBIF.

Questions people ask

Why does my phlox get white spots?: That is likely powdery mildew, which thrives when the leaves stay wet or air flow is limited.
Should I deadhead my phlox?: Yes, deadheading can encourage a second flush of blooms later in the season.

Where the name comes from

The name Phlox is Greek for flame, referring to the intense colors of the flowers. Paniculata refers to the panicle shaped flower clusters.

Good to know

The name Phlox comes from the Greek word for flame.
These plants were once used in traditional herbal medicine.
Garden phlox is native to the eastern United States.

Is your garden phlox looking unwell?

This page is a general guide. Pocket Botanist diagnoses problems from a photo of your actual plant, works out watering for your light and conditions, and reminds you when care is due.

Get the app

This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.