When to Plant Ageratum in USDA Zone 5b
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.
In Zone 5b, the average last spring frost is around April 18 and the first fall frost is around October 13, giving you a growing season of approximately 178 days.
Ageratum Planting Timeline — Zone 5b
Where Is USDA Zone 5b?
The map below highlights the states that contain Zone 5b. Click any state to see the Ageratum planting schedule for that location.
Ageratum Planting Calendar — Zone 5b
| 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 |
· 8" apart · Rows 10" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | — |
| November | — |
| December | — |
Free Zone 5b Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 5b with start dates, transplant windows, and harvest times.
Growing Conditions
Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
Days to Maturity
60–75 days
Soil pH
6 – 7
Zone Temperature Range
-15°F to -10°F average annual minimum
Growing Season
178 days (Zone 5b average)
Planting Specifications
| Plant Spacing | 8 inches apart |
| Row Spacing | 10 inches between rows |
Succession Planting Ageratum in Zone 5b
Sow every 6.9 weeks for continuous harvest throughout the season.
Growing Tips for Ageratum in Zone 5b
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.
Companion Planting
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Saving Ageratum Seeds
Recommended for Your Garden
Start seeds indoors with reusable cell trays and humidity domes.
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
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Related Plants
Ageratum in Other Zones
Ageratum 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 Ageratum in Zone 5b?
In Zone 5b, plan your Ageratum planting around the average last frost date of April 18. Start seeds indoors around February 28. Direct sow outdoors around April 25. Transplant seedlings around April 25.
Can Ageratum grow in Zone 5b?
Yes, Ageratum can grow well in Zone 5b, hardy in USDA zones 3a through 11b. Zone 5b has a growing season of approximately 178 days, which is sufficient for Ageratum (60-75 days to maturity).
When can I harvest Ageratum in Zone 5b?
In Zone 5b, expect to harvest Ageratum from June 20 – September 19. Ageratum takes 60-75 days from planting to harvest.
What is the last frost date for Zone 5b?
The average last spring frost in Zone 5b is around April 18, and the first fall frost is around October 13. This gives a growing season of approximately 178 days. These are 50% probability dates — actual frost dates vary year to year.
What should I plant next to Ageratum?
Good companion plants for Ageratum include Marigolds, Zinnias, Petunias, Salvia. These companions can help with pest control, pollination, and nutrient sharing.
Your Zone 5b Garden Planner — Free
A 22-page printable planner tailored to Zone 5b. Planting dates, monthly task lists, harvest log, seed inventory, and succession charts — everything you need to plan a full season.