When to Plant Cosmos in Alaska
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.
Alaska spans USDA hardiness zones 2a, 2b, 3b, 4a, 4b, 5a, 5b, 6b, 7a, 7b, 8a (with planting data available), so planting dates vary by your location within the state. Click your zone below for the most accurate dates.
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Click your county for exact Cosmos planting dates based on your local frost dates.
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Cosmos Planting Calendar for Alaska
▸ Zone 2a ~94 day growing season · Full guide →
Last frost: May 30 · First frost: September 1 · 94 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | May 2 | May 2 – May 16 |
| Transplant Outdoors | June 6 | Jun 6 – Jun 20 |
| Direct Sow | June 6 | Jun 6 – Jun 27 |
| Bloom | August 15 | Aug 15 – Oct 10 |
▸ Zone 2b ~111 day growing season · Full guide →
Last frost: May 22 · First frost: September 10 · 111 day season
| 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 |
▸ Zone 3b ~135 day growing season · Full guide →
Last frost: May 10 · First frost: September 22 · 135 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 12 | Apr 12 – Apr 26 |
| Transplant Outdoors | May 17 | May 17 – May 31 |
| Direct Sow | May 17 | May 17 – Jun 7 |
| Bloom | July 26 | Jul 26 – Oct 4 |
▸ Zone 4a ~145 day growing season · Full guide →
Last frost: May 6 · First frost: September 28 · 145 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 8 | Apr 8 – Apr 22 |
| Transplant Outdoors | May 13 | May 13 – May 27 |
| Direct Sow | May 13 | May 13 – Jun 3 |
| Bloom | July 22 | Jul 22 – Oct 7 |
▸ Zone 4b ~155 day growing season · Full guide →
Last frost: May 1 · First frost: October 3 · 155 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 3 | Apr 3 – Apr 17 |
| Transplant Outdoors | May 8 | May 8 – May 22 |
| Direct Sow | May 8 | May 8 – May 29 |
| Bloom | July 17 | Jul 17 – Oct 9 |
▸ Zone 5a ~166 day growing season · Full guide →
Last frost: April 25 · First frost: October 8 · 166 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 28 | Mar 28 – Apr 11 |
| Transplant Outdoors | May 2 | May 2 – May 16 |
| Direct Sow | May 2 | May 2 – May 23 |
| Bloom | July 11 | Jul 11 – Oct 3 |
▸ Zone 5b ~178 day growing season · Full guide →
Last frost: April 18 · First frost: October 13 · 178 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 21 | Mar 21 – Apr 4 |
| Transplant Outdoors | April 18 | Apr 18 – May 2 |
| Direct Sow | April 18 | Apr 18 – May 9 |
| Bloom | June 27 | Jun 27 – Sep 26 |
▸ Zone 6b ~205 day growing season · Full guide →
Last frost: April 3 · First frost: October 25 · 205 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 6 | Mar 6 – Mar 20 |
| Transplant Outdoors | April 3 | Apr 3 – Apr 17 |
| Direct Sow | April 3 | Apr 3 – Apr 24 |
| Bloom | June 12 | Jun 12 – Sep 25 |
▸ Zone 7a ~221 day growing season · Full guide →
Last frost: March 25 · First frost: November 1 · 221 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 25 | Feb 25 – Mar 11 |
| Transplant Outdoors | March 25 | Mar 25 – Apr 8 |
| Direct Sow | March 25 | Mar 25 – Apr 15 |
| Bloom | June 3 | Jun 3 – Sep 23 |
▸ Zone 7b ~235 day growing season · Full guide →
Last frost: March 18 · First frost: November 8 · 235 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 18 | Feb 18 – Mar 4 |
| Transplant Outdoors | March 11 | Mar 11 – Mar 25 |
| Direct Sow | March 11 | Mar 11 – Apr 1 |
| Bloom | May 20 | May 20 – Sep 23 |
▸ Zone 8a ~255 day growing season · Full guide →
Last frost: March 8 · First frost: November 18 · 255 day season
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 8 | Feb 8 – Feb 22 |
| Transplant Outdoors | February 22 | Feb 22 – Mar 8 |
| Direct Sow | February 22 | Feb 22 – Mar 15 |
| Bloom | May 3 | May 3 – Sep 20 |
Growing Tips for Alaska
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.
Cosmos in Other States
- Alabama
- 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 Alaska?
Planting dates for Cosmos in Alaska depend on your USDA zone. Alaska spans zones 2a, 2b, 3b, 4a, 4b, 5a, 5b, 6b, 7a, 7b, 8a. Check the planting calendar above for your specific zone's frost dates and planting windows.
What zone is Alaska for planting?
Alaska contains USDA hardiness zones 2a, 2b, 3b, 4a, 4b, 5a, 5b, 6b, 7a, 7b, 8a. Your specific zone depends on your location within the state — northern and higher-elevation areas are in colder zones, while southern and coastal areas are warmer.