When to Plant Cosmos in Champaign County, OH
Cosmos (Cosmos bipinnatus) is an airy, feathery-foliaged cottage garden annual from Mexico that thrives on neglect. It produces delicate daisy-like blooms in shades of pink, white, and magenta from midsummer until frost. Cosmos is a prolific self-sower — once established in a garden it often returns year after year without replanting. Excellent habitat plant for beneficial insects.
Champaign County, Ohio is in USDA Zone 6a. The average last spring frost is April 25 and the first fall frost is October 17, giving you a growing season of approximately 175 days.
At an elevation of 980 feet, Champaign County receives approximately 37.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Cosmos during the growing season.
Champaign County Soil Profile
Soil Type
Silt Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Cosmos Planting Timeline — Champaign County, OH
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 28 | Mar 28 – Apr 11 |
| Transplant Outdoors | April 25 | Apr 25 – May 9 |
| Direct Sow | April 25 | Apr 25 – May 16 |
| Bloom | July 4 | Jul 4 – Oct 10 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Low — drought tolerant
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: N/A
🗺️ USDA Zone
Zone 6a
📆 Growing Season
175 days in Champaign County
Growing Tips for Champaign County
Direct-sow after last frost; cosmos germinates readily at 65-80°F in 7-10 days. Avoid rich soil — excess fertility produces lush foliage at the expense of blooms. Cosmos tolerates poor, dry soil exceptionally well. Pinch seedlings at 8 inches to encourage branching. Self-sows freely; allow some seed heads to mature and drop for a no-fuss perennial effect in warm climates.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Cosmos in Other Locations
Frequently Asked Questions
When should I plant Cosmos in Champaign County, OH?
Champaign County is in Zone 6a with an average last frost of April 25. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Champaign County, OH?
Champaign County, Ohio is in USDA Hardiness Zone 6a. The average last spring frost is April 25 and first fall frost is October 17.
Your Champaign County Garden Planner — Free
A 22-page printable planner built for Champaign County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.