Spoiler I think the species is Russian Giant. According to the 1986 Guiness Book of World Records, the tallest Sunflower ever grown measured 25 feet 5 and 1/2 inches. It was grown by Martien Heijms of Oirschot in the Netherlands The largest sunflower head ever recorded by the Guinness Book of World Records measured 32 1/4 inches (82 cm) in diameter, grown by Emily Martin from Maple Ridge, Canada in the hot summer of 1983.
Spoiler At about 10 to 15 feet this sunflower is reaching for it's namesake. Helianthus annuus while not the guinness book record holder, that distinction belongs to a 26ft 4in foot behemoth grown in Gemany, on average produces the tallest flowers. With names as Mammoth Russian and Kong, Russian Giant, American Giant, Paul Bunyan and Cyclops these represent the tallest cultivars, and reach mature heights of 12 to 15 feet. The term 'tallest' is a moving target which gardeners from around the world are continually testing. Next year? Who knows. Jerry
