When to plant Sunflower in Phillips County, CO
Spring Sunflower in Phillips County goes in May 11–June 1, once nighttime temps stop dipping near freezing.
When to Plant Sunflower in Phillips County, CO
Sunflower (Helianthus annuus) is a fast-growing North American native annual famous for its towering stems and brilliant yellow heads. It thrives in full sun and heat, producing large, pollen-rich blooms that attract bees, butterflies, and seed-eating birds. Varieties range from 18-inch dwarfs to 12-foot giants and nearly every color except blue.
Phillips County, Colorado is in USDA Zone 5b. The average last spring frost is May 4 and the first fall frost is October 7, giving you a growing season of approximately 156 days.
At an elevation of 5,494 feet, Phillips County receives approximately 21.1 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Sunflower during the growing season.
Phillips County Soil Profile
Soil Type
Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Sunflower Planting Timeline — Phillips County, CO
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 13 | Apr 13 – Apr 27 |
| Transplant Outdoors | May 11 | May 11 – May 25 |
| Direct Sow | May 11 | May 11 – Jun 1 |
| Bloom | August 3 | Aug 3 – Oct 19 |
Plant 1" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Direct Sow |
| July | — |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Low — drought tolerant
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7.5 · Your soil: N/A
🗺️ USDA Zone
Zone 5b
📆 Growing Season
156 days in Phillips County
Growing Tips for Phillips County
Direct-sow 1 inch deep after last frost; germination takes 7-14 days at 65-75°F soil. Sunflowers dislike root disturbance so direct sowing is strongly preferred over transplanting. Plant in succession every 2 weeks for extended bloom. Stake tall varieties. Avoid overwatering — they tolerate drought once established. Birds will self-deadhead seed heads; leave them up through fall for wildlife.
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 Phillips County, CO?
Phillips County is in Zone 5b with an average last frost of May 4. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Phillips County, CO?
Phillips County, Colorado is in USDA Hardiness Zone 5b. The average last spring frost is May 4 and first fall frost is October 7.
When should I plant Sunflower in Phillips County, CO?
In Phillips County, CO, plant Sunflower after the last frost (around May 4) and before the first frost (around October 7). Best results when soil holds above 50°F.
What growing zone is Phillips County, CO for Sunflower?
Phillips County sits in USDA Zone 5b. Sunflower grows reliably in zones 2a through 11b, so it's a good fit here.
Can Sunflower grow in Phillips County's climate?
Yes — Sunflower grows well in Phillips County's temperate climate. Phillips County averages a 156-day frost-free season, with last frost around May 4 and first frost around October 7.
Your Phillips County Garden Planner — Free
A 22-page printable planner built for Phillips County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.