Growing Cosmos in Zone 8b
Zone 8b has warm winters and an extended growing season — excellent for heat-loving crops like Cosmos. Last frost: Mar 22. First frost: Nov 10.
Planting Calendar
Season: Mar 22 – Nov 10 (233 days)
When to Plant Cosmos in Zone 8b
Start Seeds Indoors: Feb 22
Start Cosmos seeds indoors around Feb 22 (4 weeks before last frost). Optimal germination temperature: 75°F. Germinates in 5–10 days.
Transplant Outdoors: Mar 29
Transplant Cosmos seedlings outdoors after Mar 29. Wait until soil temperature reaches 60°F. Space plants at 12/sqft. Harden off plants for a week before moving outside.
Harvest: May 23
First harvest approximately May 23 (~55 days from transplant). Continue harvesting until first frost (Nov 10).
Cosmos in Other Zones
1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b 11a 11b 12a 12b 13a 13bFrequently Asked Questions
When should I plant Cosmos in Zone 8b?
Start Cosmos seeds indoors around Feb 22. Transplant outdoors after Mar 29. Expect first harvest around May 23.
What is the last frost date for Zone 8b?
The average last spring frost date for Zone 8b is Mar 22. The first fall frost averages Nov 10, giving a 233-day growing season.
Can I grow Cosmos in Zone 8b?
Yes. Cosmos needs 55 days to harvest. Zone 8b has a 233-day growing season, which is sufficient.
What is the best month to plant Cosmos in Zone 8b?
The best time to start Cosmos in Zone 8b is Feb. Begin seeds indoors around Feb 22, then transplant outdoors after the last frost date of Mar 22.
How long does Cosmos take to harvest?
Cosmos takes approximately 55 days from planting to harvest. In Zone 8b, expect your first harvest around May 23.
Plan Your Cosmos Garden
Track Cosmos from seed to harvest with personalized frost dates, watering recommendations, and companion planting visualization.
Start Free Cosmos Growing Guide