How to Grow Cosmos

A warm-season flower for the home garden across the warmer US.

Cosmos are a rewarding warm-season crop for backyard growers.

When to plant

Plant Cosmos in spring once the soil has warmed and all frost has passed. In the warmest regions a second crop is possible in late summer. See your region on the cosmos page for exact timing.

Varieties

• Sensation, Tall pink and white classic (Botanical Interests)
• Sonata, Compact, earlier blooming (Park Seed)

How to grow it

• Sun & soil: full sun, rich well-drained soil with even moisture.
• Spacing: about 30 cm (12 in) between plants.
• Sowing: barely cover the seed.
• Water: roughly 3 L per plant every 3 days in hot weather.
• Containers: grows well in a pot of 25cm+.

Pests & problems

Watch for Aphids and Thrips. In humid regions, Powdery mildew and Aster yellows can appear, so space for airflow and water at the roots in the morning.

Harvest

Cosmos are usually ready to harvest in about 2 months. Pick regularly to keep plants productive.

When to plant in your region

Pick your region to see exactly when to plant cosmos where you garden.

See also: Cosmos in the plant library →

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