The undisputed giant of the garden, the Mammoth Sunflower is a spectacular sight to behold. Reaching staggering heights of up to 12 feet, these towering plants feature massive, heavy-petaled heads supported by thick, woody stalks. This single-stem variety is a fast and vigorous grower, making it the perfect choice for creating natural privacy screens, competing for the "tallest flower" in the neighborhood, or harvesting delicious seeds.
Seed & Planting Care
To reach their record-breaking heights, Mammoth Sunflowers need a strong start and plenty of room to grow.
Sowing Method: Direct sow seeds into the garden after the danger of frost has passed and the soil has warmed. Sunflowers have deep taproots and generally do not like to be moved once planted.
Sowing Depth: Plant seeds 1" deep to ensure they have enough soil anchorage to support their future height.
Spacing: Space plants 18–24" apart. Crowding these giants can lead to thinner stalks that may tip over in the wind.
Support: While the stalks are very thick, planting them near a fence or providing a sturdy stake can help protect these 12-foot giants during heavy summer storms.
Sun & Water: Plant in full sun (at least 6–8 hours a day). These vigorous growers are "heavy drinkers," so ensure they receive consistent water, especially as the flower heads begin to form.
Growing & Harvest Profile
Days to Maturity: 110 days.
Growth Habit: Single-stemmed (produces one massive flower head per plant).
Vigor: Fast-growing and incredibly resilient once established.
Seed Count: Approximately 20 seeds per 2 grams.
Uses & Wildlife
Edible Seeds: The massive heads produce a bounty of large, striped seeds perfect for roasting and snacking.
For the Birds: If left in the garden over winter, the dried heads serve as a natural bird feeder, attracting chickadees, finches, and nuthatches.
Garden Impact: Provides excellent shade and a dramatic vertical element to any landscape.
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