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Plant care

Garden Phlox 'David' (Garden phlox) care

Phlox paniculata 'David'

Also called Garden phlox, Tall phlox.

RHS H7USDA 4-8Pet-safeIndoor 90-120 cm tall and 60-90 cm wide.

Watering rhythm

5-7days

When the top 3-4 cm of soil is dry, about every 5-7 days

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Light

Direct sun (at least 4-6 hours)

Soil

Rich, moist, well-drained loam

Humidity

40-70%

Temp

-29 to 30°C

Pet safety

Pet-safe

Mature size

90-120 cm tall and 60-90 cm wide.

Care at a glance

Light

Most houseplants will scorch where garden phlox 'david' thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. Full sun (6+ hours) for sturdy stems and heavy bloom; tolerates light shade but flowering thins and stems stretch. Good sun and airflow keep its noted mildew resistance at its best. A plant moved abruptly from low light to direct sun bleaches in 48 hours — always acclimatise over a week.

Watering

Aim for when the top 3-4 cm of soil is dry, about every 5-7 days for garden phlox 'david', but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Keep consistently moist, roughly 2-3 cm of water weekly; never let it dry out fully while blooming. Water at the base to keep foliage dry and minimise mildew.

Soil and pot

Garden Phlox 'David' grows best in rich, moist, well-drained loam. Fertile, humus-rich soil that stays evenly moist yet drains freely, pH 6.0-7.0. Mulch to conserve moisture and keep roots cool. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Garden Phlox 'David' sits happiest at around 40-70% humidity and -29 to 30°C (-20 to 86°F). A hardy border perennial tolerant of typical outdoor humidity. 'David' is bred for mildew resistance, but crowded, humid plantings still benefit from spacing and airflow. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed garden phlox 'david' sparingly. Moderate feeder. Top-dress with compost in spring and apply a balanced fertiliser as growth begins; a second light feed before flowering supports the large panicles. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on garden phlox 'david' in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Powdery mildew — 'David' is highly mildew-resistant but not immune; ensure good airflow, divide congested clumps and avoid wetting the foliage.
  • Spider mites — Stippled, bronzed leaves in hot, dry weather; keep plants watered and rinse foliage, treating with insecticidal soap if needed.
  • Floppy stems — In too much shade or rich soil stems stretch and flop; grow in full sun and thin weak stems in spring for self-support.
  • Reverted seedlings — Self-sown seedlings rarely come true and often revert to magenta; deadhead spent panicles to prevent seeding-out of the white form.

Propagation

Best by division in spring or autumn, or by basal stem or root cuttings. Seed does not come true to the white 'David', so use vegetative methods to keep the cultivar. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Garden Phlox 'David' is pet-safe. The ASPCA lists Phlox as non-toxic to cats and dogs, with no recognised toxic principle. As with any plant, nibbling foliage may cause mild, transient gastrointestinal upset. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435 in the US, or Animal PoisonLine on 01202 509 000 in the UK).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Garden Phlox 'David' care — frequently asked questions

What is the common name for Phlox paniculata 'David'?

Phlox paniculata 'David' is most commonly called Garden Phlox 'David', but it is also known as Garden phlox, Tall phlox. The names refer to the same species, so care instructions for Garden Phlox 'David' apply identically to anything sold as Garden phlox.

How much light does garden phlox 'david' need?

Garden Phlox 'David' grows best in direct sun (at least 4-6 hours). Full sun (6+ hours) for sturdy stems and heavy bloom; tolerates light shade but flowering thins and stems stretch. Good sun and airflow keep its noted mildew resistance at its best.

How often should I water garden phlox 'david'?

Water garden phlox 'david' when the top 3-4 cm of soil is dry, about every 5-7 days. Keep consistently moist, roughly 2-3 cm of water weekly; never let it dry out fully while blooming. Water at the base to keep foliage dry and minimise mildew. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is garden phlox 'david' toxic to cats and dogs?

Garden Phlox 'David' is pet-safe. The ASPCA lists Phlox as non-toxic to cats and dogs, with no recognised toxic principle. As with any plant, nibbling foliage may cause mild, transient gastrointestinal upset.

What USDA hardiness zone does garden phlox 'david' grow in?

Garden Phlox 'David' is rated for USDA zone 4-8 and RHS hardiness H7. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Garden Phlox 'David' deep-dive guides

Every aspect of garden phlox 'david' care, each with its own calibrated guide:

Featured in these plant shortlists

Garden Phlox 'David' qualifies for 9 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

  • Best pet-safe houseplants — Houseplants the ASPCA lists as non-toxic to cats and dogs — every one verified against the ASPCA toxic and non-toxic plant list.
  • Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
  • Best pet-safe flowering plants — Flowering houseplants the ASPCA lists as non-toxic to cats and dogs — colour and blooms in a pet home, without the worry.
  • Best pet-safe plants for bright light — Non-toxic to cats and dogs and happy in a bright, sunny spot — safe plants for your best-lit windowsill.
  • Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
  • Best houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
  • Best fragrant houseplants — Indoor plants with scented flowers or aromatic foliage — greenery you can smell, selected from our care library.
  • Best cat-safe plants — Houseplants the ASPCA lists as non-toxic to cats (and dogs) — safe greenery for a home with a curious cat.
  • Best dog-safe plants — Houseplants the ASPCA lists as non-toxic to dogs (and cats) — safe greenery for a home with a curious dog.
  • Browse all 30 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Garden Phlox 'David' is also commonly called Garden phlox or Tall phlox.