When to Plant Ageratum in Alaska

Ageratum (Ageratum houstonianum), the floss flower, produces clusters of fluffy, powder-puff blooms in the rare sky-blue and lavender tones difficult to find among warm-season annuals. Compact mounding habit makes it ideal as a front-of-border edging plant. Blooms from early summer through fall with minimal deadheading; heat and humidity tolerant once established.

Alaska spans USDA hardiness zones 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 Ageratum planting dates based on your local frost dates.

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Ageratum Planting Calendar for Alaska

▸ 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	March 15	Mar 15 – Mar 29
Transplant Outdoors	May 24	May 24 – Jun 7
Direct Sow	May 24	May 24 – Jun 14
Bloom	July 19	Jul 19 – Sep 20

▸ 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	March 11	Mar 11 – Mar 25
Transplant Outdoors	May 13	May 13 – May 27
Direct Sow	May 13	May 13 – Jun 3
Bloom	July 8	Jul 8 – Sep 16

▸ 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	March 13	Mar 13 – Mar 27
Transplant Outdoors	May 8	May 8 – May 22
Direct Sow	May 8	May 8 – May 29
Bloom	July 3	Jul 3 – Sep 18

▸ 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 7	Mar 7 – Mar 21
Transplant Outdoors	May 2	May 2 – May 16
Direct Sow	May 2	May 2 – May 23
Bloom	June 27	Jun 27 – Sep 19

▸ 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	February 28	Feb 28 – Mar 14
Transplant Outdoors	April 25	Apr 25 – May 9
Direct Sow	April 25	Apr 25 – May 16
Bloom	June 20	Jun 20 – Sep 19

▸ 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	February 13	Feb 13 – Feb 27
Transplant Outdoors	April 3	Apr 3 – Apr 17
Direct Sow	April 3	Apr 3 – Apr 24
Bloom	May 29	May 29 – Sep 11

▸ 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 11	Feb 11 – Feb 25
Transplant Outdoors	March 25	Mar 25 – Apr 8
Direct Sow	March 25	Mar 25 – Apr 15
Bloom	May 20	May 20 – Sep 9

▸ 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 4	Feb 4 – Feb 18
Transplant Outdoors	March 18	Mar 18 – Apr 1
Direct Sow	March 18	Mar 18 – Apr 8
Bloom	May 13	May 13 – Sep 16

▸ 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	January 25	Jan 25 – Feb 8
Transplant Outdoors	March 1	Mar 1 – Mar 15
Direct Sow	March 1	Mar 1 – Mar 22
Bloom	April 26	Apr 26 – Sep 13

Growing Tips for Alaska

Start seeds indoors 6–8 weeks before last frost — do not cover seed; it needs light to germinate. Can be direct-sown after last frost once soil warms to 60°F. Transplant or thin to proper spacing after frost danger passes. Deadheading isn't strictly required but tidying spent clusters improves appearance. Provide consistent moisture; drought causes premature setting. Avoid deep shade — blooms best in full sun to light afternoon shade.

Ageratum in Other States

Frequently Asked Questions

When should I plant Ageratum in Alaska?

Planting dates for Ageratum in Alaska depend on your USDA zone. Alaska spans zones 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 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.

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