When to Plant Sunflower in Costilla County, CO
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.
Costilla County, Colorado is in USDA Zone 5a. The average last spring frost is June 8 and the first fall frost is September 16, giving you a growing season of approximately 100 days.
At an elevation of 5,598 feet, Costilla County receives approximately 21 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Sunflower during the growing season.
Costilla County Soil Profile
Soil Type
Loam
Soil pH
6.2-8.3
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 6/10 — consider drought-tolerant varieties and mulching
Sunflower Planting Timeline — Costilla County, CO
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 13 | Apr 13 – Apr 27 |
| Transplant Outdoors | June 22 | Jun 22 – Jul 6 |
| Direct Sow | June 15 | Jun 15 – Jul 6 |
| Harvest | August 31 | Aug 31 – Oct 19 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | — |
| June | Transplant Outdoors Direct Sow |
| July | Transplant Outdoors Direct Sow |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| 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
100 days
Growing Tips for Costilla 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 Costilla County, CO?
Costilla County is in Zone 5a with an average last frost of June 8. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Costilla County, CO?
Costilla County, Colorado is in USDA Hardiness Zone 5a. The average last spring frost is June 8 and first fall frost is September 16.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Costilla County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.
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