Mammoth Sunflower is an heirloom, open-pollinated sunflower variety that produces towering stalks that can grow to 12′ tall. The sunflower heads are also mammoth as they’ll average 8-14″ in diameter. The sturdy stalks ensure these plants will remain standing, even in high winds. We recommend planting these in summer and then using the stalks for a pole bean trellis in the fall.
Mammoth Sunflower is a great variety for attracting pollinators and feeding the native bee populations around your garden. The yellow petals do a great job of providing visual cues for pollinators, and the dark brown disks are full of pollen to feed them. The seeds can also be harvested for roasting once the sunflowers are done blooming and the heads have dried.
Mammoth Sunflower can be direct-seeded or transplanted. Direct-seeding can be easily done with a walk-behind planter like our Hoss Garden Seeder. We recommend using a #3 seed plate and modifying the hole size to fit the variety being planted. Sunflower seed size can vary greatly from one variety to the next, therefore it’s important to always calibrate the seed plate hole size for the variety being planted. Sunflowers grow well when planted on double rows with drip irrigation. Lay one row of drip tape and plant on both sides of the tape to maximize garden space.
Sunflowers also perform well when transplanted. They grow great in our heavy-duty seed starting trays. Transplants are ready to go in the ground when plants can be easily pulled from the seed starting trays. For increased storage potential, harvest sunflowers when blooms are closed. Blooms will then open when cut and placed into a container with water.
Mammoth Sunflower Planting Information
Planting Method: transplant or direct seed
When to Plant: after last frost
Planting Depth: 1/2″
Seed Spacing: 4-6″
Row Spacing: 2-3′
Days to Maturity: 75
Disease Resistance: None