Garden Cosmos (Cosmos bipinnatus)

Garden Cosmos

Cosmos bipinnatus

Feathery foliage carries daisy-like blooms, a soft summer cloud. Annual flowering herb; common names: garden cosmos, Mexican aster.

Full sun
1–2/week
Beginner
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Plant Needs

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Sunlight Full sun exposure for abundant blooms; tolerates light partial shade in extremely hot climates to prevent leaf scorch
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Watering Water deeply when the top 2–3 cm of soil is dry; avoid overwatering to prevent root rot and fungal issues
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Temperature Thrives in warm temperate to warm temperatures; is frost-tender and will die back with frost exposure
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Characteristics

  • Leaf: Finely bipinnate, feathery, bright green, fern-like texture
  • Flower: Daisy-like composite heads, 5–10 cm diameter; colors include white, pink, magenta, orange, yellow
  • Stem: Slender, branching, green to reddish-brown, slightly hairy
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Care Guide

Watering

Keep soil consistently moist but not waterlogged; water deeply during prolonged dry spells

Fertilization

Light, diluted feed once every 4 weeks if soil is nutrient-poor. Avoid over-fertilizing, as this can lead to excessive foliage growth at the expense of blooms

Banana peel compost tea:Soak fully composted banana peels in water for 24 hours; dilute the tea 1:20 with water before applying as a root drench to promote abundant blooms
Pruning
  • Deadhead spent blooms regularly to encourage continuous flowering throughout the growing season
  • Pinch back young seedlings when they reach 10–15 cm tall to promote bushier growth and more flower stems
  • Remove leggy or damaged stems to maintain a compact, tidy habit
  • Cut back entire plants to ground level after flowering to tidy garden beds and prepare for next season
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA confirmed non-toxic to cats; no harmful effects from ingestion

Humans: Non-toxic to humans; no known adverse health effects from ingestion or contact

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Garden Uses & Culture

Culture: Symbolizes peace, love, and harmony; a popular cottage garden staple

Usage: Cut flower for floral arrangements, garden ornamental, and pollinator plant to support bees and butterflies