When to Plant Ageratum in Pennsylvania

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.

Pennsylvania spans USDA hardiness zones 5b, 6a, 6b, 7a, 7b (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 Pennsylvania

▸ 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 6a ~193 day growing season · Full guide →

Last frost: April 10 · First frost: October 20 · 193 day season

Activity	When	Date Range
Start Indoors	February 20	Feb 20 – Mar 6
Transplant Outdoors	April 10	Apr 10 – Apr 24
Direct Sow	April 10	Apr 10 – May 1
Bloom	June 5	Jun 5 – Sep 11

▸ 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

Growing Tips for Pennsylvania

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 Pennsylvania?

Planting dates for Ageratum in Pennsylvania depend on your USDA zone. Pennsylvania spans zones 5b, 6a, 6b, 7a, 7b. Check the planting calendar above for your specific zone's frost dates and planting windows.

What zone is Pennsylvania for planting?

Pennsylvania contains USDA hardiness zones 5b, 6a, 6b, 7a, 7b. 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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