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Aster

Aster novi-belgii

FlowersPerennialFrost Hardy

Late-season bloomer providing essential nectar for pollinators heading into autumn. Star-shaped flowers in purple, blue, pink, and white.

Overview

SunFull Sun
WaterMediumCalculate watering amount
Height30–100 cm
Spread40 cm
Spacing30 cm
Row Spacing35 cm
Germination10–14 days
To Harvest80–105 days

Companion Planting

Bad Companions

None

Toxicity

SeverityNon-toxic

Asters are listed as non-toxic to dogs, cats, and humans by the ASPCA; no known toxic compounds.

Planting Tips

LocationFull sun (6+ hours direct sunlight); tolerates light partial shade but blooms best in full sun.
SoilWell-drained, loamy soil with a slightly acidic to neutral pH (6.0–7.0); amend heavy clay with compost.
Sowing Depth0.5 cm
Planting Depth5 cm
WateringWater deeply once per week; keep soil consistently moist but never waterlogged, especially during establishment.

1 cm of water per m² equals 10 liters. Use the Watering Calculator for exact amounts.

FertilizingApply a balanced slow-release fertilizer (10-10-10) once in early spring; avoid over-fertilizing to prevent leggy growth.

Care Tip: Pinch stem tips back by half in late spring/early summer to encourage bushier habit and more blooms; divide clumps every 2–3 years.

Common Pests

Aphids

Symptoms: Curled or distorted new growth, sticky honeydew on leaves, and possible sooty mold.

Treatment: Spray with insecticidal soap or a strong jet of water; apply neem oil for heavy infestations.

Prevention: Encourage beneficial insects such as ladybugs; avoid excessive nitrogen fertilization.

Lace Bugs

Symptoms: Stippled, bleached upper leaf surfaces with dark, varnish-like excrement on undersides.

Treatment: Apply neem oil or insecticidal soap to leaf undersides; use systemic insecticide for severe cases.

Prevention: Maintain plant vigor with adequate watering; plant in locations with good air circulation.

Spider Mites

Symptoms: Fine stippling on leaves, bronzing, and delicate webbing on leaf undersides, especially in hot dry weather.

Treatment: Spray foliage forcefully with water; apply miticidal soap or horticultural oil if populations persist.

Prevention: Keep plants well-watered during dry spells; avoid dusty conditions near plantings.

Common Diseases

Powdery Mildew

Symptoms: White, powdery fungal coating on leaves and stems, leading to leaf curling and premature drop.

Treatment: Apply sulfur-based or potassium-bicarbonate fungicide; remove and dispose of heavily infected foliage.

Prevention: Space plants for good air circulation; choose mildew-resistant cultivars; water at the base, not overhead.

Aster Wilt (Fusarium oxysporum)

Symptoms: Sudden wilting of stems on one side of the plant, yellowing lower leaves, and eventual plant death.

Treatment: No chemical cure; remove and destroy infected plants immediately to limit soil contamination.

Prevention: Rotate planting sites on a 3–4 year cycle; grow wilt-resistant varieties; ensure well-drained soil.

Aster Yellows (Phytoplasma)

Symptoms: Stunted growth, green or deformed flowers, yellowed and bushy foliage (witches' broom effect).

Treatment: No cure exists; remove and destroy infected plants promptly to prevent spread.

Prevention: Control leafhopper vectors with row covers or insecticidal soap; remove nearby weed hosts.