When to Plant Sunflower in Harmon County, OK
Sunflowers are tall, cheerful annuals grown for their edible seeds and as pollinator magnets. They come in sizes from 2-foot dwarfs to 12-foot giants.
Harmon County, Oklahoma is in USDA Zone 7b. The average last spring frost is March 31 and the first fall frost is November 5, giving you a growing season of approximately 219 days.
At an elevation of 993 feet, Harmon County receives approximately 34.4 inches of rainfall annually with predominantly loam soil. Summer highs average 91°F, providing good warmth for Sunflower during the growing season.
Harmon County Soil Profile
Soil Type
Loam
Soil pH
6.5-7.5
Drainage
Well Drained
Plant 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 Harmon County
How your county's soil matches Sunflower's growing requirements.
Soil pH
Your soil pH (6.5–7.5) is within Sunflower's preferred range (6.0–7.5).
Soil Texture
The loam soil in Harmon County is excellent for Sunflower — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.0%) — Sunflower will thrive.
How to Plant Sunflower
Succession Planting Sunflower
Sow every 8 weeks. Last sowing by Jul 28 to harvest before frost.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Sunflower Planting Timeline — Harmon County, OK
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 10 | Feb 10 – Feb 24 |
| Transplant Outdoors | April 14 | Apr 14 – Apr 28 |
| Direct Sow | April 7 | Apr 7 – Apr 28 |
| Harvest | June 23 | Jun 23 – Aug 11 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | — |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 7b
📆 Growing Season
219 days in Harmon County
Growing Tips for Sunflower in Harmon County
Direct sow Sunflower outdoors after March 31 in Harmon County when soil has warmed and frost danger has passed.
Common pests for Sunflower 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. Stake tall varieties in windy areas. Harvest seed heads when the back turns brown and seeds are plump. Dry heads upside down.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Sunflower in Other Locations
Frequently Asked Questions
When should I plant Sunflower in Harmon County, OK?
Harmon County is in Zone 7b with an average last frost of March 31. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Harmon County, OK?
Harmon County, Oklahoma is in USDA Hardiness Zone 7b. The average last spring frost is March 31 and first fall frost is November 5.
Plan Your Garden with Confidence
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