Mammoth Sunflower Seeds, Giant Heirloom Open Pollinated

Mammoth Sunflower Seeds, the classic towering heirloom with single golden heads up to 12 inches across. Open-pollinated, pollinator-favorite, and unbeatable for edible seed harvest and backyard showstoppers.

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✅ Germination Promise: if your seeds fail to germinate under proper growing conditions, contact us within one year and we will replace them or refund your purchase. See the details.

The original giant sunflower. Mammoth grows 9 to 12 feet tall on a single thick stalk, crowned with one enormous golden-yellow flower head that can reach 12 inches or more across. Bees and pollinators swarm it all summer, and the plump gray-striped seeds are prized for roasting, bird feeding, or saving for next year.

• Type: Annual (Helianthus annuus)
• Height: 9 to 12 ft
• Bloom: Single large head, up to 12 in diameter
• Color: Golden yellow
• Days to bloom: 80 to 90 days
• Sun: Full sun
• Seed count: choose 20 seeds or 50 seeds per packet

Direct sow after last frost, 1 inch deep, 18 to 24 inches apart. Stake tall stalks in windy Kansas gardens. Open-pollinated, save your own seed for next season.

🌻 See our Kansas growing guide →

Growing Guide: How to Grow Sunflowers in Kansas: A Zone 6b Guide - planting dates, spacing, watering, and harvest tips for Zone 6b.