Sunflower
Helianthus annuus
Sunflowers are tall, cheerful annuals that double as a living trellis for cucumbers and produce pollen-rich flowers that attract an enormous range of beneficial insects. Their allelopathic root exudates can suppress weeds but also inhibit beans and peas.
Growing Conditions
Sunlight
Full Sun
Water Needs
Low
Soil
Well-draining loam; pH 6.0–7.5; tolerates poor soil
Spacing
12–24 inches
Days to Maturity
70–100 days from direct sow
Growing Zones
Thrives in USDA Zones 3–11
Companion Planting
Keep Away From
When to Plant
Direct Sow
After last frost, soil 50°F+
Harvest
Cut flowers when outer petals are opening; harvest seeds when back of head turns yellow-brown
Organic Growing Tips
Plant sunflowers as living trellises at the north end of beds so they do not shade shorter crops.
Leave seed heads standing through winter as an invaluable food source for birds and wildlife.
Keep well away from bean and pea beds — sunflower allelopathy reduces their germination and yield.
Sow in succession every 2–3 weeks for a season-long display that continuously supports pollinators.
Common Pests
- Birds
- Aphids
- Sunflower Moth
- Downy Mildew
All pest management in Garden uses safe, organic, non-toxic methods only. No synthetic pesticides, ever.