The sunflower family includes over 20,000 distinct species. They are Compositae a diverse family of flowering plants that includes perennials and annuals. Other members of the same plant family include marigolds, dandelions and daisies. Among the Compositae family are several species commonly referred to as Giant Sunflowers, some as big as trees. The Tallest Sunflower ever recorded came from the Netherlands and was over 25 feet tall. In 1983 a giant sunflower blossom was documented as slightly under 3 feet in circumference.
Some of the Giant Sunflower varieties Include the following.
Mongolian Giant 12 to 14 feet in height. 80 to 90 days till maturity. Bloom Size 16 to 18 inches across.
Kong Giant [Not to be confused with Kong Hybrid] Claims of 24 feet in height with 16 to 18 inch Bloom size.
American Giant Hybrid 12 to 16 feet in height. 80 to 90 days till maturity. Bloom Size up to 10 inch average.
Mammoth Russian 8 to 10 feet in height. 80 to 90 days till maturity. Bloom Size up to 14 inches.
Skyscraper Sunflower 10 to 12 feet in height. 80 to 90 days till maturity. Produces multiple flower heads 12 to 14 inch circumference.
The easiest way to start sunflowers is by direct seeding, planting the seed directly in the ground where you intend to grow it. It can however be started indoors in cell-packs or peat pots.
If starting them outdoors, the soil temperature should be at least 55 - 60 degrees F and all possibilities of a late frost passed.
Some gardeners plant a few scattered here and there [keep them away from potatoes and beans] while others grow them in monocultured rows. In a small cluster or row they should be seeded about 6 inches apart with the seeds planted about 1.5 inches deep.
See: How to Grow Sunflowers for detailed planting and care information.
pH 6.0 to 7.5
Soil temp. 55 to 60F Minimum
Direct Seed Spacing 6 inches
Seed Depth 1.5 inches deep
Germination 10 to 14 days *
Maturity 75 - 120 days *
Sunflower Seed Preperation Purple Cone Flower Passion Flower
Calendula Chamomile Hibiscus
Electric Daisies Dandelions Edible Flowers
* Depending on cultivar, climate and conditions.