When to Plant Sunflower in Adams County, ID
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.
Adams County, Idaho is in USDA Zone 5a. The average last spring frost is May 20 and the first fall frost is September 25, giving you a growing season of approximately 128 days.
At an elevation of 6,593 feet, Adams County receives approximately 20.6 inches of rainfall annually with predominantly loam soil. Summer highs average 85°F, providing good warmth for Sunflower during the growing season.
Adams County Soil Profile
Soil Type
Loam
Soil pH
6.3-8
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.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Sunflower Planting Timeline — Adams County, ID
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 25 | Mar 25 – Apr 8 |
| Transplant Outdoors | June 3 | Jun 3 – Jun 17 |
| Direct Sow | May 27 | May 27 – Jun 17 |
| Harvest | August 12 | Aug 12 – Sep 30 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Low — drought tolerant
Days to Maturity
70–100 days
Soil pH
6 – 7.5
USDA Zone
Zone 5a
Growing Season
128 days
Growing Tips for Adams County
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 Adams County, ID?
Adams County is in Zone 5a with an average last frost of May 20. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Adams County, ID?
Adams County, Idaho is in USDA Hardiness Zone 5a. The average last spring frost is May 20 and first fall frost is September 25.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Adams County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.
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