When to Plant Sunflower in Cedar County, IA
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.
Cedar County, Iowa is in USDA Zone 5a. The average last spring frost is April 17 and the first fall frost is October 16, giving you a growing season of approximately 182 days.
At an elevation of 1,112 feet, Cedar County receives approximately 41 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87°F, providing good warmth for Sunflower during the growing season.
Cedar County Soil Profile
Soil Type
Silt Loam
Soil pH
5.9-6.9
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 Cedar County
How your county's soil matches Sunflower's growing requirements.
Soil pH
Your soil pH (5.9–6.9) overlaps with Sunflower's range (6.0–7.5), though not a perfect match.
Soil Texture
The silt loam soil in Cedar County is excellent for Sunflower — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Sunflower.
Organic Matter
Organic matter is moderate (3.9%). Annual compost additions will help Sunflower.
How to Plant Sunflower
Succession Planting Sunflower
Sow every 8 weeks. Last sowing by Jul 08 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Sunflower
Sunflower 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 | Sunflower Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 2.8" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3.4" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 5.1" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 5.3" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 4.9" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 4.7" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 3.2" | 0" | ✅ Rainfall sufficient |
| Nov | — | 3" | 0" | ❄️ Dormant |
| Dec | — | 2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Cedar County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Sunflower 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.
Sunflower Planting Timeline — Cedar County, IA
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 20 | Feb 20 – Mar 6 |
| Transplant Outdoors | May 1 | May 1 – May 15 |
| Direct Sow | April 24 | Apr 24 – May 15 |
| Harvest | July 10 | Jul 10 – Aug 28 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| 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: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
182 days in Cedar County
Growing Tips for Sunflower in Cedar County
Direct sow Sunflower outdoors after April 17 in Cedar 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
Check more plant combinations with our Companion Planting Checker →
Sunflower in Other Locations
Frequently Asked Questions
When should I plant Sunflower in Cedar County, IA?
Cedar County is in Zone 5a with an average last frost of April 17. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Cedar County, IA?
Cedar County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is April 17 and first fall frost is October 16.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Cedar County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.