When to Plant Cosmos in USDA Zone 2b
What to do in June
If you only do a handful of things in the garden this June, make it these. They're sequenced around your zone's frost timing.
Send me my free Zone 2b Planting Guide →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.
In Zone 2b, the average last spring frost is around May 22 and the first fall frost is around September 10, giving you a growing season of approximately 111 days.
Cosmos Planting Timeline — Zone 2b
Where Is USDA Zone 2b?
The map below highlights the states that contain Zone 2b. Click any state to see the Cosmos planting schedule for that location.
Cosmos Planting Calendar — Zone 2b
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 24 | Apr 24 – May 8 |
| Transplant Outdoors | May 29 | May 29 – Jun 12 |
| Direct Sow | May 29 | May 29 – Jun 19 |
| Bloom | August 7 | Aug 7 – Oct 9 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Start Indoors Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Free Zone 2b Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 2b with start dates, transplant windows, and harvest times.
Growing Conditions
Sun
Full Sun (6-8+ hours)
💧 Water
Low — drought tolerant
Days to Maturity
60–90 days
Soil pH
6 – 8
Zone Temperature Range
-45°F to -40°F average annual minimum
Growing Season
111 days (Zone 2b average)
Planting Specifications
| Planting Depth | 0.3 inches |
| Plant Spacing | 12 inches apart |
| Row Spacing | 18 inches between rows |
Succession Planting Cosmos in Zone 2b
Sow every 6.9 weeks for continuous harvest throughout the season.
Growing Tips for Cosmos in Zone 2b
Zone 2b has a short growing season (~111 days). Start Cosmos indoors early and use season-extension techniques like row covers and cold frames.
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.
Companion Planting
Good Companions
The Gardener's Encyclopedia to Companion Planting
The pairings that make vegetables, herbs, and flowers grow better — and the ones that quietly wreck a bed.
- Proven pairings for 200+ vegetables, herbs, flowers, and fruits
- Full seed-starting + planting schedule with timing and spacing
- Bonus: square-foot gardening guide + printable seasonal planners
Saving Cosmos Seeds
Recommended for Your Garden
Full-spectrum LED lights for starting seeds indoors when daylight is limited.
Warm soil for faster germination of heat-loving crops like tomatoes and peppers.
Protect plants from frost, wind, and pests while letting light and water through.
Related Plants
Cosmos in Other Zones
Cosmos by State
- 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
Frequently Asked Questions
When should I plant Cosmos in Zone 2b?
In Zone 2b, plan your Cosmos planting around the average last frost date of May 22. Start seeds indoors around April 24. Direct sow outdoors around May 29. Transplant seedlings around May 29.
Can Cosmos grow in Zone 2b?
Yes, Cosmos can grow well in Zone 2b, hardy in USDA zones 2a through 11b. Zone 2b has a growing season of approximately 111 days, which is sufficient for Cosmos (60-90 days to maturity).
When can I harvest Cosmos in Zone 2b?
In Zone 2b, expect to harvest Cosmos from August 7 – October 9. Cosmos takes 60-90 days from planting to harvest.
What is the last frost date for Zone 2b?
The average last spring frost in Zone 2b is around May 22, and the first fall frost is around September 10. This gives a growing season of approximately 111 days. These are 50% probability dates — actual frost dates vary year to year.
What should I plant next to Cosmos?
Good companion plants for Cosmos include Marigolds, Zinnias, Basil, Tomatoes. These companions can help with pest control, pollination, and nutrient sharing.
Your Zone 2b Garden Planner — Free
A 22-page printable planner tailored to Zone 2b. Planting dates, monthly task lists, harvest log, seed inventory, and succession charts — everything you need to plan a full season.