When to Plant Phlox in Alaska

Garden Phlox (Phlox paniculata) is a beloved native perennial of eastern North America, producing large, domed clusters of fragrant flowers atop upright stems from mid-summer into fall. Its sweet honey-like fragrance carries on summer evenings and draws hummingbirds, butterflies, and sphinx moths. Modern cultivars offer colors spanning white, pink, salmon, red, purple, and bicolors. A classic cottage garden stalwart, phlox combines well with black-eyed Susans, echinacea, and ornamental grasses in naturalistic plantings. Select mildew-resistant cultivars for best long-term performance.

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 Phlox planting dates based on your local frost dates.

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Phlox 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 1	Mar 1 – Mar 15
Transplant Outdoors	May 24	May 24 – Jun 7
Direct Sow	May 24	May 24 – Jun 14
Bloom	August 16	Aug 16 – Oct 11

▸ 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	February 25	Feb 25 – Mar 11
Transplant Outdoors	May 20	May 20 – Jun 3
Direct Sow	May 20	May 20 – Jun 10
Bloom	August 12	Aug 12 – Oct 14

▸ 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	February 20	Feb 20 – Mar 6
Transplant Outdoors	May 15	May 15 – May 29
Direct Sow	May 15	May 15 – Jun 5
Bloom	August 7	Aug 7 – Oct 16

▸ 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	February 21	Feb 21 – Mar 7
Transplant Outdoors	May 9	May 9 – May 23
Direct Sow	May 9	May 9 – May 30
Bloom	July 25	Jul 25 – Oct 10

▸ 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 14	Feb 14 – Feb 28
Transplant Outdoors	May 2	May 2 – May 16
Direct Sow	May 2	May 2 – May 23
Bloom	July 18	Jul 18 – Oct 10

▸ 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	January 30	Jan 30 – Feb 13
Transplant Outdoors	April 10	Apr 10 – Apr 24
Direct Sow	April 10	Apr 10 – May 1
Bloom	June 19	Jun 19 – 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	January 21	Jan 21 – Feb 4
Transplant Outdoors	April 1	Apr 1 – Apr 15
Direct Sow	April 1	Apr 1 – Apr 22
Bloom	June 10	Jun 10 – Sep 2

▸ 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	January 14	Jan 14 – Jan 28
Transplant Outdoors	March 25	Mar 25 – Apr 8
Direct Sow	March 25	Mar 25 – Apr 15
Bloom	June 3	Jun 3 – Aug 26

▸ 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 11	Jan 11 – Jan 25
Transplant Outdoors	March 8	Mar 8 – Mar 22
Direct Sow	March 8	Mar 8 – Mar 29
Bloom	May 17	May 17 – Jul 26

Growing Tips for Alaska

Start seeds indoors 8–10 weeks before last frost, or transplant container divisions in spring. Named cultivar seeds may not come true; divisions from named plants are the preferred propagation method. Space generously (18–24 inches) and avoid overhead watering to reduce powdery mildew risk. Good air circulation is critical — thin clumps to the strongest 5–7 stems per plant in spring. Deadhead after the primary bloom flush to encourage secondary flowering. Division every 2–3 years in spring keeps plants vigorous. Fall planting of divisions (Zones 5+) is equally effective. Year 2+ plants develop into full clumps with the most prolific bloom.

Phlox in Other States

Frequently Asked Questions

When should I plant Phlox in Alaska?

Planting dates for Phlox 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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