When to Plant and Harvest Sunflower
Tall single-stem sunflower grown for giant heads, edible seeds, and dramatic garden structure
Pets: Not on the ASPCA list. The ASPCA Sunflower entry is swamp sunflower (Helianthus angustifolius), listed as non-toxic. Common sunflower is not listed by species. Pet-Safe Garden Finder
Best Time and Place to Plant Sunflower
In USDA zone 7, the typical spring window is April 10 to May 25. Cooler zones usually plant later; warmer zones plant earlier.
Plant Mammoth Sunflower in a spot with 8+ hours of direct sun, soil warmed to 55F to 75F, and enough room for 18 inches between plants and 36 inches between rows.
Related Planting Guides
Planting Windows by Zone
| Zone | Spring | Fall |
|---|---|---|
| Zone 1 | June 1 to June 20 | Spring only |
| Zone 2 | May 20 to June 15 | Spring only |
| Zone 3 | May 10 to June 10 | Spring only |
| Zone 4 | May 1 to June 5 | Spring only |
| Zone 5 | April 25 to June 1 | Spring only |
| Zone 6 | April 20 to May 30 | Spring only |
| Zone 7 | April 10 to May 25 | Spring only |
| Zone 8 | March 25 to May 15 | Spring only |
| Zone 9 | March 10 to May 1 | August 1 to September 15 |
| Zone 10 | February 15 to April 15 | August 15 to October 1 |
| Zone 11 | January 15 to March 15 | September 1 to November 1 |
| Zone 12 | January 1 to March 1 | October 1 to December 1 |
| Zone 13 | Year-round | Year-round |
Spacing and Care
- Planting depth: 1 inches deep
- Spacing: 18 inches apart, 36 inches between rows
- Soil temperature: 55F to 75F
- Sunlight: 8+ hours
- Watering: Water deeply during establishment and flowering; mature plants tolerate short dry spells
- Days to harvest: 100
Fertilization
- Compost organic: Work 2 inches into soil before planting
- Balanced 10-10-10 synthetic: Light feeding when plants are knee-high if soil is poor
Companion Plants
- Corn
- Cucumbers
- Squash
- Nasturtium
Avoid Planting Near
- Potatoes
- Low-light crops nearby
Check any pair, and see which pairings have research behind them, on the Companion Planting Desk.
Harvest Signs
- Back of head turns yellow-brown
- Seeds are plump and loosen from the head
- Petals have dried and fallen
- Cover heads if birds are harvesting first
Track picks and rate the season on the Harvest Log.
FAQs
When should I plant Sunflower?
Sunflower planting depends on your USDA hardiness zone. In USDA zone 7, the typical spring window is April 10 to May 25. Cooler zones usually plant later; warmer zones plant earlier.
What is the best time of year to plant Sunflower?
The best time of year to plant Sunflower is when your zone planting window is open and soil temperatures are around 55F to 75F. In USDA zone 7, the typical spring window is April 10 to May 25. Cooler zones usually plant later; warmer zones plant earlier.
Where is the best place to plant Sunflower?
Plant Mammoth Sunflower in a spot with 8+ hours of direct sun, soil warmed to 55F to 75F, and enough room for 18 inches between plants and 36 inches between rows.
How far apart should I plant Sunflower?
Plant Sunflower about 18 inches apart, with rows around 36 inches apart.
What grows well with Sunflower?
Sunflower is commonly paired with Corn, Cucumbers, Squash, Nasturtium.
How long does Sunflower take to grow?
Sunflower is typically ready to harvest in about 100 days under good conditions. Use the harvest signs below rather than the calendar alone.
How do I know when to harvest Sunflower?
Harvest Sunflower when back of head turns yellow-brown. Seeds are plump and loosen from the head Petals have dried and fallen