Cosmos Planting Guide

June

Your June guide to cosmos

Some notes on cosmos care that hold up no matter where you garden — then check your zone for specifics.

Sun full sun

Water low

Days to harvest 60–90

Plant depth 0.3″

Spacing 12″

How to water cosmos
Mulch heavily around cosmos to hold soil moisture without watering more often.
Where to put cosmos
South-facing beds are ideal for cosmos. Shade from nearby trees or fences costs real production.
Check your local forecast before planting
Your zone determines the exact week to plant cosmos. Pick your county below and we'll line everything up against your frost dates.

Show me cosmos timing for my zone →

Cosmos (Cosmos bipinnatus) is an airy, feathery-foliaged cottage garden annual from Mexico that thrives on neglect. It produces delicate daisy-like blooms in shades of pink, white, and magenta from midsummer until frost. Cosmos is a prolific self-sower — once established in a garden it often returns year after year without replanting. Excellent habitat plant for beneficial insects.

Cosmos bipinnatus · Flower · Asteraceae family · 60–90 days to maturity

Annual Blooms in Summer Pollinator-friendly Good for cutting

Why it matters: If you're just starting a flower garden in your area, Cosmos is a forgiving first pick. It tolerates imperfect soil, mild drought, and the occasional missed watering. The reward: weeks (sometimes months) of continuous color.

Get Your Personalized Cosmos Planting Dates

Enter your ZIP code to see exact planting dates, soil compatibility, and growing tips specific to your county.

Where Can You Grow Cosmos?

Zone Compatibility for Cosmos Zones 2a – 11b

1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b 11a 11b 12a 12b 13a 13b

Ideal (data available) Suitable Marginal Not recommended

Planting Dates by Zone

Zone	Start Indoors	Direct Sow	Transplant	Bloom
Zone 2a	May 2	Jun 6	Jun 6	Aug 15 – Oct 10
Zone 2b	Apr 24	May 29	May 29	Aug 7 – Oct 9
Zone 3a	Apr 17	May 22	May 22	Jul 31 – Oct 9
Zone 3b	Apr 12	May 17	May 17	Jul 26 – Oct 4
Zone 4a	Apr 8	May 13	May 13	Jul 22 – Oct 7
Zone 4b	Apr 3	May 8	May 8	Jul 17 – Oct 9
Zone 5a	Mar 28	May 2	May 2	Jul 11 – Oct 3
Zone 5b	Mar 21	Apr 18	Apr 18	Jun 27 – Sep 26
Zone 6a	Mar 13	Apr 10	Apr 10	Jun 19 – Sep 25
Zone 6b	Mar 6	Apr 3	Apr 3	Jun 12 – Sep 25
Zone 7a	Feb 25	Mar 25	Mar 25	Jun 3 – Sep 23
Zone 7b	Feb 18	Mar 11	Mar 11	May 20 – Sep 23
Zone 8a	Feb 8	Feb 22	Feb 22	May 3 – Sep 20
Zone 8b	Jan 28	Feb 4	Feb 4	Apr 15 – Sep 16
Zone 9a	Jan 13	Jan 13	Jan 13	Mar 24 – Sep 8
Zone 9b	Dec 28	Dec 21	Dec 21	Mar 1 – Aug 30
Zone 10a	Dec 4	Nov 20	Nov 20	Jan 29 – Aug 13
Zone 10b	Dec 4	Nov 13	Nov 13	Jan 22 – Aug 20
Zone 11a	Dec 4	Nov 6	Nov 6	Jan 15 – Aug 27
Zone 11b	Dec 4	Oct 30	Oct 30	Jan 8 – Sep 3

How to Plant Cosmos

0.3"

Planting Depth

12"

Between Plants

18"

Between Rows

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

Low — drought tolerant

Drought tolerant — water only when soil is dry 2" deep.

🧪 Soil pH

6 – 8

Prefers neutral to slightly acidic soil — ideal for most garden beds.

🗺️ Hardiness Zones

Zone 2a – 11b

📅 Days to Maturity

60–90 days

Quick-growing crop. Multiple plantings per season are possible.

👪 Plant Family

Asteraceae

Rotate with other families yearly to prevent soil-borne diseases. Don't plant in the same spot where Asteraceae family crops grew last year.

Succession Planting Cosmos

Cosmos matures in just 60–90 days, making it ideal for succession planting. In a typical 180-day growing season, you can get up to 3 successive plantings by sowing every 6.9 weeks.

Your actual succession count depends on your local frost dates. Enter your ZIP code to get personalized succession planting dates for your area.

Companion Planting for Cosmos

✅ Good Companions

Marigolds Zinnias Basil Tomatoes Beans

Check more combinations with our Companion Planting Checker →

Growing Tips for Cosmos

Direct-sow after last frost; cosmos germinates readily at 65-80°F in 7-10 days. Avoid rich soil — excess fertility produces lush foliage at the expense of blooms. Cosmos tolerates poor, dry soil exceptionally well. Pinch seedlings at 8 inches to encourage branching. Self-sows freely; allow some seed heads to mature and drop for a no-fuss perennial effect in warm climates.

Saving Cosmos Seeds

Recommended for Your Garden

🌱

Seed Starting Trays $8-20

Start seeds indoors with reusable cell trays and humidity domes.

🧪

Soil Test Kit $12-25

Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.

🏷️

Garden Plant Markers $6-12

Keep your garden organized with durable, weather-resistant plant labels.

Reader favourite

Seed Saving & Storage Guide

$27 $157 value

Most saved seeds go bad before next season. This shows exactly when to pick, how to dry, and where to store seeds from 200 plants so yours don't.

200 plants, step-by-step: life cycle, pollination type, isolation
Exact temperature + humidity ranges that keep seeds viable
Bonus: searchable Google Sheets tracker + custom GPT assistant

Save a lifetime of seed money →

Cosmos by State

Frequently Asked Questions

How long does it take to grow Cosmos?

Cosmos (Cosmos bipinnatus) takes 60 to 90 days from planting to harvest. Exact timing depends on your variety, growing conditions, and USDA zone.

What zones can Cosmos grow in?

Cosmos can be grown in USDA zones 2a through 11b. Use the planting calendar above to find the exact dates for your zone.

How much sun does Cosmos need?

Growing Cosmos requires Full Sun (6-8+ hours), Low — drought tolerant, and soil pH of 6 to 8.