How to Grow Cosmos
Get Your Exact Cosmos Planting Dates
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Ready to grow Cosmos?
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🛠️ Supplies You'll Need
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🌿 Plant Overview
☀️ Growing Requirements
☀️
Sun
Full Sun (6-8 hours)
💧
Water
Low-Moderate
↔️
Spacing
18" apart
🌱
Depth
0.25" deep
📏
Height
24-60"
🌱
Germination
7-14 days
Ready to Grow Cosmos?
Find quality seeds from trusted suppliers.
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🌾 Seed Saving Guide
🟢 EasyWhen to Harvest Seed
Harvest narrow seed heads when flower petals drop and the base turns brown and dry.
Processing
Pull seeds directly from dried flower heads, dry 1 week in an open envelope.
Seed Viability
Up to 3 years when stored cool, dark, and dry.
Pro Tip
Cosmos cross freely within the species — isolate by 150 feet from other cosmos for pure color.
Seed Storage Supplies
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Raised Bed Planting Guides
A 4×8 bed fits 14 plants of Cosmos. See plant counts, spacing grids, and companion pairings for every bed size →
Cosmos Planting Calendar by Zone
Cosmos Planting Calendar by State
Other Plants
Frequently Asked Questions
When should I plant Cosmos? +
Sow Cosmos seeds directly in the garden 0 weeks before your last frost date. Use the search on this page to find exact dates for your location.
How long does Cosmos take to grow? +
Cosmos typically matures in about 60 days from planting. Exact timing varies by variety, soil conditions, and local climate.
Should I start Cosmos indoors or direct sow? +
Cosmos does best when direct sown outdoors. Plant seeds directly in the garden at the appropriate time based on your local frost dates.
How much sun does Cosmos need? +
Cosmos requires full sun (6-8 hours) to thrive.
How far apart should I plant Cosmos? +
Space Cosmos plants 18 inches apart to allow adequate airflow and root development.
How much water does Cosmos need? +
Cosmos has low-moderate water needs. Consistent moisture is important especially during germination and early growth.
Can you save seeds from Cosmos? +
Yes — seed saving difficulty for Cosmos is rated easy. Harvest narrow seed heads when flower petals drop and the base turns brown and dry. Pull seeds directly from dried flower heads, dry 1 week in an open envelope.
How long do Cosmos seeds last in storage? +
Properly dried and stored Cosmos seeds remain viable for up to 3 years. Store in a cool, dark, dry location in an airtight container with a silica gel packet for best results.
Are Cosmos seeds open-pollinated? +
Yes — Cosmos is open-pollinated, meaning seeds saved from your harvest will grow plants true to the parent variety. This makes it an excellent candidate for building a self-sustaining garden.
About Cosmos
Airy, feathery annual with daisy-like blooms in pink, white, and burgundy. Self-seeds readily, blooms prolifically all season, and attracts bees and butterflies.
Expect your Cosmos to be ready for harvest in approximately 60 days from planting.
Use the search above or browse by zone or state to find the perfect planting dates for your location.