🌻 Sunflower
Helianthus annuus
flowers
annual
Asteraceae
☀️ Sun
full sun
💧 Water
moderate (deep roots provide some drought tolerance)
🗺️ Zones
2-11 (as annual)
🧪 Soil pH
6.0-7.5
🪴 Soil Type
loamy, sandy, tolerates wide range
🚿 Drainage
well-drained
📏 Spacing
12-24 inches (ornamental), 18-30 inches (seed production)
📐 Height
2-15 feet (depending on variety)
⏱️ Maturity
55-120 days (depending on variety)
Key:🤝 Grows well together❌ Keep apart☀️ Sun needs💧 Water🗺️ Hardiness zone
🤝 Companions (18)
Sunflowers interplanted with corn in extended Three Sisters systems attract pollinators and beneficial insects; mutual wind protection.
Cosmos flowers attract hoverflies and parasitic wasps that control sunflower pests; both are heat-loving annuals thriving with minimal care.
Cucumbers may benefit from light shade in very hot climates, but sunflowers are allelopathic and aggressive water competitors. Their root exudates can inhibit cucumber growth. If interplanting, maintain significant distance and monitor for stunting. Not recommended by university extension sources.
Lettuce may tolerate some afternoon shade from sunflowers in hot weather. However, sunflowers are allelopathic and their root exudates can inhibit lettuce growth. Plant with caution and monitor for stunting. Better alternatives for lettuce shade include pole beans or trellised cucumbers.
🤝 Melon
Melons sprawl beneath sunflowers as living mulch; sunflowers provide wind protection and deep roots don't compete with melon's shallow system.
Morning glory vines can climb sunflower stalks for support; this combination works well in ornamental gardens.
Sunflowers provide wind protection for tall okra plants; attract pollinators for okra flowers.
🤝 Pea (climbing)
Climbing peas use sunflower stalks as living trellises; peas fix nitrogen and are harvested before sunflower heads become heavy , a classic pairing.
Classic companion , beans climb sunflower stalks as living trellis
Pumpkins tolerate sunflower allelopathy better than many crops; large leaves shade out weeds beneath sunflowers.
Traditional companion in Eastern Europe and Asia
Squash can tolerate some sunflower allelopathy better than other crops; squash leaves shade soil, reducing moisture competition. However, sunflowers are allelopathic overall and better suited as garden edge plantings rather than close interplanting. The traditional Fourth Sister concept in Native American agriculture typically refers to Cleome or amaranth, not sunflowers.
Zinnias and sunflowers share growing conditions and attract the same pollinators; bright flowers create stunning summer borders.
⚠️ Keep Apart (8)
⚠️ Bean (Pole)
Sunflowers release root exudates that inhibit bean seed germination and stunt growth; they should not be planted together despite the 'pole' temptation
Brassicas suffer from sunflower allelopathy; growth stunted and yields reduced in soil where sunflower roots have exuded chemicals.
Fennel is severely allelopathic to sunflowers; root exudates inhibit germination and suppress growth , never plant together.
Mustard and sunflowers have antagonistic root interactions; combined allelopathic compounds create a doubly toxic soil environment.
Sunflower root exudates persistently inhibit bean germination; even the following season, bean seeds may struggle in former sunflower soil.
Sunflowers are strongly allelopathic to potatoes , they inhibit tuber development, reduce yields, and increase susceptibility to blight
Sunflowers compete aggressively for soil moisture and nutrients; their allelopathic compounds suppress tomato growth and fruit set
📝 Growing Notes
Sunflowers exhibit heliotropism , young flower heads track the sun across the sky (east to west), a phenomenon that stops once flowers mature and face east permanently. Sunflowers are allelopathic , their roots, leaves, and seed hulls release chemicals that inhibit the growth of nearby plants, particularly potatoes, pole beans, and grass crops. They are heavy feeders that deplete soil nutrients rapidly. The deep taproot (up to 6+ feet) mines nutrients and breaks up compacted soil, but also aggressively competes for water. Sunflowers are excellent phytoremediators , they absorb heavy metals (lead, arsenic, uranium) from contaminated soil and were famously used after Chernobyl and Fukushima.
🛒 Buy Seeds & Plants
Baker Creek Heirloom Seeds
Johnny's Selected Seeds
Botanical Interests
True Leaf Market
Burpee
Territorial Seed Company
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