Mammoth Black Russian Sunflower
This sunflower has a giant yellow flower head, up to 15″ across with on a single, tall stalk, 12′ – 15′. The seeds of Mammoth Black Russian have a high oil content. This sunflower cultivar traveled to Europe where it was further cultivated into this giant. Great for bird seed mixes. Thin seedlings to 2′ – 3′ apart. These may need support against a wall or fence in windy areas and will do better if planted with composted manure and slow release fertilizer. Allow the heads to dry completely before removing the seeds.
Keep them deadheaded until the end of the season. If you deadhead your sunflowers, they will keep pumping out new blossoms in their will to create seeds and more sunflowers. Don’t cut the stalk way back, the next sunflower often forms just inches from the place you deadheaded.
Leave the very last batch of spent flowers for the birds and for next year’s flowers. When it seems like the sunflowers are slowing down, leave the last set of flower heads on the plant for the birds. Even if it is a little ugly going into Fall, birds like the seed heads right on the plant. Little finches especially like to sit on top of the old brown seed head and bend over and pluck seeds out.
Height: 12-15 feet
Seeding rates for sunflowers:
If you are planning to grow a plot of sunflower plants and not just a decorative patch, you will need to consider the size of the individual plants and plant the seed accordingly. For a generic sized sunflower plant, plan on a seeding rate of 15,000 – 25,000 plants/ acre. That is around 3-4 lbs of seed/acre. (The giant sunflower plants such as Grey Stripe and Black Russian will need to be planted farther apart.) If you aren’t going as large as a whole acre, that breaks down to around 625 plants/ 1,000 sq feet, about 2 oz of seed. You will need to increase this amount if you plan to plant thicker and thin down to the strongest plant. Planting sunflowers closer together will result in more smaller flowers, farther apart fewer larger flowers. Plant no more than 1 inch deep into loose, fertile soil, in direct sun after the danger of frost is past when the soil temperatures are around 55 – 60 deg. Plant about 12 inches apart in rows about 30 inches apart. Ideally thin the weakest plants until you have 1 plant per 2-3 sq ft.