Sunflower
Helianthus annuus • Asteraceae
🌱 Seed Category
Flower / Gear / Oilseed
🌍 Origin Region
North America; widely adapted globally in temperate and subtropical regions
📅 Days to Maturity
80-120 days; harvest when the back of the flower head turns yellow/brown and seeds are plump.
🌡️ Hardiness Zones
USDA Zones 2-11 (Annual); very sensitive to hard freezes.
About This Seed
Seeds (achenes) are large, teardrop-shaped, with a hard woody hull featuring grey and white longitudinal stripes. The resulting plant is a tall, erect annual reaching 6-12 feet with large heart-shaped leaves and massive yellow-petaled composite flower heads.
Growing Information
Growing Season
Spring to early Summer; direct sow after last frost; low frost tolerance
Germination
7-14 days; optimal soil temperature 70-85°F (21-29°C); high germination rate; light not required for germination; no pre-treatment necessary.
Planting Instructions
Depth: 1 inch; Spacing: 12-18 inches; Row Spacing: 24-36 inches; Well-drained soil; pH 6.0-7.5; requires heavy feeding (compost recommended).
Sunlight & Water Needs
Full Sun (6-8+ hours); moderate watering; high drought tolerance once established; avoid waterlogged soil.
Companion Plants
Beneficial: Corn, Squash, Cucumbers (provides shade/support). To avoid: Potatoes and Pole Beans (sunflowers can inhibit growth through allelopathy).
Special Characteristics
Highly attractive to pollinators (bees/butterflies); edible seeds; seeds attract birds; hyperaccumulator (cleans soil of heavy metals); heat tolerant.