80 Days to maturity. Helianthus annuus. Organic Black Mammoth Sunflower Seeds: Non-GMO. Open Pollinated. Ornamental. Annual. The Black Mammoth sunflower is striking and grows up to 10 feet tall and is topped with 12 inches diameter flower heads. The petals are a classic yellow around silky black centers filled with edible seeds. These giant sunflowers are sure to put a smile on any face who sees them! Approximately 400 Seeds / Ounce.