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Plant care

Aster 'October Skies' (Aromatic Aster) care

Symphyotrichum oblongifolium 'October Skies'

Also called Aromatic Aster, Fall Aster, Oblongleaf Aster.

RHS H7USDA 3-9Pet-safeIndoor 30-45 cm tall and 60-90 cm wide

Watering rhythm

10-14days

When the top 5 cm of soil is dry, roughly every 10-14 days once established

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Light

Direct sun (at least 4-6 hours)

Soil

Average to lean, well-drained loam or sandy loam

Humidity

30-60%

Temp

−35 to 35°C

Pet safety

Pet-safe

Mature size

30-45 cm tall and 60-90 cm wide

Care at a glance

Light

Most houseplants will scorch where aster 'october skies' thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. Thrives in full sun (6+ hours daily). Reduced sunlight causes lax, floppy growth and fewer flowers. Site in an open, unshaded position for best performance. 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 5 cm of soil is dry, roughly every 10-14 days once established for aster 'october skies', 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. Highly drought-tolerant after the first growing season. Water regularly during establishment (first summer). Avoid overwatering or waterlogged soil, which encourages root rot.

Soil and pot

Aster 'October Skies' grows best in average to lean, well-drained loam or sandy loam. Tolerates poor soils well and actually performs better without heavy feeding. Rich, fertile soils encourage floppy stems. Ensure excellent drainage; does not tolerate wet feet. 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

Aster 'October Skies' sits happiest at around 30-60% humidity and −35 to 35°C (−31 to 95°F). Adapted to typical outdoor humidity in USDA zones 3-9. Good air circulation reduces the already-low risk of foliar disease on this mildew-resistant cultivar. If you keep the room above −35 to 35°C 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 aster 'october skies' sparingly. Apply a balanced slow-release fertiliser (e.g., 10-10-10) lightly in early spring. Avoid high-nitrogen feeds, which promote excessive foliage at the expense of flowers. 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 aster 'october skies' in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Powdery mildew — Rare on 'October Skies' compared to other asters, but possible in humid, stagnant-air conditions. Improve air circulation.
  • Floppy stems — Caused by excess shade or nitrogen. Grow in full sun with lean soil, or cut back by one-third in early summer (Chelsea chop) to promote bushiness.
  • Aster yellows (phytoplasma) — Causes distorted, yellowing growth. Spread by leafhoppers; remove and destroy affected plants and control leafhoppers.
  • Aphids — May cluster on new growth in spring. Knock off with a strong water spray or apply insecticidal soap.
  • Root rot — Occurs in poorly drained or constantly wet soils. Ensure good drainage and avoid overwatering, especially in heavy clay.

Companion plants

Aster 'October Skies' pairs well with Rudbeckia fulgida, Panicum virgatum, Salvia nemorosa, and Echinacea purpurea. These are species with similar light and water needs, so you can group them in the same room or on the same shelf and water as a batch.

Propagation

Divide clumps in early spring every 2-3 years to maintain vigour. Can also be propagated by stem cuttings taken in late spring or from seed sown indoors 6-8 weeks before last frost. 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

Aster 'October Skies' is pet-safe. Symphyotrichum oblongifolium is not listed as toxic to dogs or cats by the ASPCA. Asters in the Symphyotrichum genus are generally considered non-toxic, though ingestion of large amounts may cause mild 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).

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.

Aster 'October Skies' care — frequently asked questions

What is the common name for Symphyotrichum oblongifolium 'October Skies'?

Symphyotrichum oblongifolium 'October Skies' is most commonly called Aster 'October Skies', but it is also known as Aromatic Aster, Fall Aster, Oblongleaf Aster. The names refer to the same species, so care instructions for Aster 'October Skies' apply identically to anything sold as Aromatic Aster.

How much light does aster 'october skies' need?

Aster 'October Skies' grows best in direct sun (at least 4-6 hours). Thrives in full sun (6+ hours daily). Reduced sunlight causes lax, floppy growth and fewer flowers. Site in an open, unshaded position for best performance.

How often should I water aster 'october skies'?

Water aster 'october skies' when the top 5 cm of soil is dry, roughly every 10-14 days once established. Highly drought-tolerant after the first growing season. Water regularly during establishment (first summer). Avoid overwatering or waterlogged soil, which encourages root rot. 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 aster 'october skies' toxic to cats and dogs?

Aster 'October Skies' is pet-safe. Symphyotrichum oblongifolium is not listed as toxic to dogs or cats by the ASPCA. Asters in the Symphyotrichum genus are generally considered non-toxic, though ingestion of large amounts may cause mild gastrointestinal upset.

What USDA hardiness zone does aster 'october skies' grow in?

Aster 'October Skies' is rated for USDA zone 3-9 and RHS hardiness H7. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Aster 'October Skies' deep-dive guides

Every aspect of aster 'october skies' care, each with its own calibrated guide:

Featured in these plant shortlists

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

Related guides

Aster 'October Skies' is also known as Aromatic Aster, Fall Aster, and Oblongleaf Aster.