When to Plant Cosmos in Ashtabula County, OH
Ashtabula County, Ohio gardeners: here's your June plan
Welcome to June in Zone 6a. These are the moves that will have the biggest impact on your growing season.
July will be here before you know it — start on
- First harvests: cosmos
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.
Ashtabula County, Ohio is in USDA Zone 6a. The average last spring frost is April 29 and the first fall frost is October 22, giving you a growing season of approximately 176 days.
At an elevation of 963 feet, Ashtabula County receives approximately 32.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Cosmos to ensure they mature before fall.
Ashtabula County Soil Profile
Soil Type
Silt Loam
Soil pH
5.8-6.8
Drainage
Well Drained
Cosmos Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Ashtabula County
How your county's soil matches Cosmos's growing requirements.
Soil pH
Your soil pH (5.8–6.8) overlaps with Cosmos's range (6.0–8.0), though not a perfect match.
Soil Texture
The silt loam soil in Ashtabula County is excellent for Cosmos — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.5%) — Cosmos will thrive.
How to Plant Cosmos
Succession Planting Cosmos
Sow every 6.9 weeks. Last sowing by Jul 24 to harvest before frost.
Cosmos Water Budget
Monthly Watering Guide for Cosmos
Cosmos needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Cosmos Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.2" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 2" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3.2" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 4.1" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 3.1" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 2.9" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 2.5" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.4" | 0" | ❄️ Dormant |
| Dec | — | 1.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Ashtabula County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Cosmos Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Cosmos Planting Timeline — Ashtabula County, OH
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 1 | Apr 1 – Apr 15 |
| Transplant Outdoors | April 29 | Apr 29 – May 13 |
| Direct Sow | April 29 | Apr 29 – May 20 |
| Bloom | July 8 | Jul 8 – Oct 14 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| 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
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: acceptable
🗺️ USDA Zone
Zone 6a
📆 Growing Season
176 days in Ashtabula County
Growing Tips for Cosmos in Ashtabula County
Direct sow Cosmos outdoors after April 29 in Ashtabula County when soil has warmed and frost danger has passed.
Common pests for Cosmos in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
General growing tips
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 Ashtabula County, OH?
Ashtabula County is in Zone 6a with an average last frost of April 29. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Ashtabula County, OH?
Ashtabula County, Ohio is in USDA Hardiness Zone 6a. The average last spring frost is April 29 and first fall frost is October 22.
Your Ashtabula County Garden Planner — Free
A 22-page printable planner built for Ashtabula 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.