How to Grow Cosmos

Updated June 2026

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

What it looks like as it grows

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 12 in between plants.
Sowing: barely cover the seed.
Water: roughly 0.8 gal per plant every 3 days in hot weather.
Containers: grows well in a pot of 10 in+.

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 what to plant this month

Pick your region for a month-by-month calendar tuned to your climate.

Find your region →