When to Plant Sunflower in Petersburg Borough, AK
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.
Petersburg Borough, Alaska is in USDA Zone 7a. The average last spring frost is April 23 and the first fall frost is October 20, giving you a growing season of approximately 180 days.
At an elevation of 974 feet, Petersburg Borough receives approximately 17.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 57°F, so choose short-season varieties of Sunflower to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Sunflower successfully. Mulch heavily to conserve soil moisture.
Petersburg Borough Soil Profile
Soil Type
Silt Loam
Soil pH
4.9-6.3
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
Sunflower Planting Timeline — Petersburg Borough, AK
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 5 | Mar 5 – Mar 19 |
| Transplant Outdoors | May 7 | May 7 – May 21 |
| Direct Sow | April 30 | Apr 30 – May 21 |
| Harvest | July 16 | Jul 16 – Sep 3 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| 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 7a
Growing Season
180 days
Growing Tips for Petersburg Borough
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 Petersburg Borough, AK?
Petersburg Borough is in Zone 7a with an average last frost of April 23. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Petersburg Borough, AK?
Petersburg Borough, Alaska is in USDA Hardiness Zone 7a. The average last spring frost is April 23 and first fall frost is October 20.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Petersburg Borough gardeners in Zone 7a organize planting dates, track what's growing, and never miss a planting window.
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