Cosmos bipinnatus

Seed Treatment 

  • Soaking: Soak seeds in warm water for a few hours before planting to speed up germination.

Sowing Instructions

  1. Best Time to Sow – After the last frost when soil temperatures are above 60°F (16°C).

  2. Soil Requirements – Well-draining, moderately fertile soil; prefers slightly sandy or loamy soil. Avoid excessive fertilization, which can result in more foliage and fewer flowers.

  3. Sowing Depth – 1/8 inch (3 mm) deep; lightly cover with soil.

  4. Spacing –

    • Direct sowing: Space seeds 6–12 inches (15–30 cm) apart.

    • Starting indoors: Sow in biodegradable pots 4–6 weeks before the last frost, then transplant.

  5. Watering – Keep soil evenly moist during germination but avoid overwatering.

  6. Temperature for Germination – 70–75°F (21–24°C).

  7. Germination Time – 7–14 days, depending on conditions.

Care After Germination

  • Sunlight – Requires full sun (6+ hours daily) for best blooms.

  • Watering – Drought-tolerant but benefits from occasional deep watering.

  • Fertilization – Minimal fertilization needed; too much nitrogen reduces flowering.

  • Support – Taller varieties may need staking or support to prevent bending.

  • Deadheading – Regularly remove spent flowers to encourage continuous blooming.

  • Self-seeding – Cosmos readily reseeds, so leave some flowers to dry if you want new plants next season.

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