Annual Flower

When to Plant Cosmos

Delicate, daisy-like blooms that dance in the breeze. Cosmos thrive in poor soil and practically grow themselves.

Sun

Full sun (6-8 hours)

Water

Low — drought tolerant

Days to Harvest

60-90

Difficulty

beginner

Spacing

12"

Frost Tolerance

none

The Short Answer

Start cosmos seeds indoors 4 weeks before your last frost, or direct sow after frost danger has passed. Enter your zip code on our homepage tool for exact dates.

How to Grow Cosmos

Cosmos are the lazy gardener's best friend — they thrive on neglect. Rich soil and fertilizer produce lanky plants with few flowers; poor soil and drought produce compact, floriferous plants. It's one of the rare garden situations where less effort produces better results. Cosmos bipinnatus (Sensation type) produces the classic feathery foliage and large flowers in white, pink, and crimson. Cosmos sulphureus (Bright Lights) has broader leaves and warm-toned flowers in orange, yellow, and red. Both self-seed prolifically — you may only need to plant cosmos once.

Starting Seeds Indoors

Begin cosmos seeds indoors 4 weeks before your average last frost date. Seeds need soil temperatures of at least 60°F to germinate, which typically takes 5-10 days. Provide 12 hours of light per day using a south-facing window or grow lights.

Transplanting

Move seedlings outside 1 weeks after your last frost date, once soil temperatures reach 60°F. Harden off seedlings for 5 days before transplanting by gradually exposing them to outdoor conditions.

Direct Sowing

Cosmos can be direct sown 1 weeks after your last frost date. Plant seeds 0.25" deep, spaced 12" apart.

Growing Tips

Don't over-fertilize — rich soil produces more leaves and fewer flowers. Let some flowers go to seed for next year's crop.

Companion Planting

Good companions:

Tomatoes Squash

Cosmos Planting Dates by State

Click your state for cosmos planting dates specific to your location:

Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming

Note: Planting dates are based on average frost dates from NOAA Climate Normals (30-year averages). Actual conditions vary year to year. Always check your local forecast before planting frost-sensitive crops.

Last reviewed: March 29, 2026