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Plant care

Annual Phlox 'Sugar Stars' (Annual phlox) care

Phlox drummondii 'Sugar Stars'

Also called Annual phlox, Drummond phlox.

RHS H3USDA 2-11Pet-safeIndoor 20-30 cm tall and 20-25 cm wide.

Watering rhythm

4-7days

When the top 2-3 cm of soil is dry, about every 4-7 days

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Light

Direct sun (at least 4-6 hours)

Soil

Fertile, well-drained loam

Humidity

40-60%

Temp

10-27°C

Pet safety

Pet-safe

Mature size

20-30 cm tall and 20-25 cm wide.

Care at a glance

Light

Annual Phlox 'Sugar Stars' needs sun on the leaves, not just bright ambient room light. Full sun (at least 6 hours) for compact, floriferous plants; too little light causes legginess and sparse bloom. Light afternoon shade helps extend flowering in hot summers. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Water annual phlox 'sugar stars' when the top 2-3 cm of soil is dry, about every 4-7 days. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Keep evenly moist while flowering; roughly 2-3 cm of water weekly. Water at the base to keep foliage dry and reduce powdery mildew, the genus's main weakness.

Soil and pot

Annual Phlox 'Sugar Stars' grows best in fertile, well-drained loam. Moist but free-draining, moderately fertile soil rich in organic matter, pH 6.0-7.5. Avoid heavy, waterlogged ground, which encourages root rot. 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

Annual Phlox 'Sugar Stars' sits happiest at around 40-60% humidity and 10-27°C (50-80°F). An outdoor annual unconcerned by ambient humidity, but humid, stagnant air dramatically increases powdery mildew, so prioritise spacing and airflow. If you keep the room above 10 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 annual phlox 'sugar stars' sparingly. Moderate feeder. Enrich soil with compost at planting and feed every 3-4 weeks with a balanced liquid fertiliser through the bloom season to keep flowers coming. 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 annual phlox 'sugar stars' in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Powdery mildew — The classic phlox problem; white film in humid, crowded plantings. Space plants, improve airflow and avoid overhead watering.
  • Leggy growth — Stretches and flowers poorly in too little light; pinch young plants and grow in full sun to keep them bushy.
  • Heat-induced decline — Bloom slows in peak summer heat; shear lightly and provide afternoon shade to coax a fresh flush.
  • Spider mites — Fine stippling and webbing in hot, dry spells; rinse foliage and treat with insecticidal soap if populations build.

Propagation

From seed. Direct-sow after frost or start indoors 6-8 weeks early; seed germinates best in darkness, so cover lightly. Cultivar seedlings may show some colour variation. 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

Annual Phlox 'Sugar Stars' 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.

Annual Phlox 'Sugar Stars' care — frequently asked questions

What is the common name for Phlox drummondii 'Sugar Stars'?

Phlox drummondii 'Sugar Stars' is most commonly called Annual Phlox 'Sugar Stars', but it is also known as Annual phlox, Drummond phlox. The names refer to the same species, so care instructions for Annual Phlox 'Sugar Stars' apply identically to anything sold as Annual phlox.

How much light does annual phlox 'sugar stars' need?

Annual Phlox 'Sugar Stars' grows best in direct sun (at least 4-6 hours). Full sun (at least 6 hours) for compact, floriferous plants; too little light causes legginess and sparse bloom. Light afternoon shade helps extend flowering in hot summers.

How often should I water annual phlox 'sugar stars'?

Water annual phlox 'sugar stars' when the top 2-3 cm of soil is dry, about every 4-7 days. Keep evenly moist while flowering; roughly 2-3 cm of water weekly. Water at the base to keep foliage dry and reduce powdery mildew, the genus's main weakness. 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 annual phlox 'sugar stars' toxic to cats and dogs?

Annual Phlox 'Sugar Stars' 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 annual phlox 'sugar stars' grow in?

Annual Phlox 'Sugar Stars' is rated for USDA zone 2-11 (grown as a warm-season annual) and RHS hardiness H3. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Annual Phlox 'Sugar Stars' deep-dive guides

Every aspect of annual phlox 'sugar stars' care, each with its own calibrated guide:

Featured in these plant shortlists

Annual Phlox 'Sugar Stars' qualifies for 11 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 small & tabletop houseplants — Compact houseplants that stay under about 40 cm — desk, shelf and windowsill plants that never outgrow a small space.
  • 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.
  • Best small pet-safe plants — Compact, tabletop houseplants that are also ASPCA non-toxic to cats and dogs — safe greenery for a desk or shelf.
  • Browse all 30 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Annual Phlox 'Sugar Stars' is also commonly called Annual phlox or Drummond phlox.