Sunflower

The sunflower is an annual plant native to the Americas in the family Asteraceae, with a large flowering head. The stalk of the flower can breed as high as 3 metres tall, with the flower head reaching up to 30 cm in length with the "large" seeds. The term "sunflower" is also used to refer to all plants of the genus Helianthus, many of which are permanent plants.

What is typically called the flower is actually a head of many flowers (florets) crowded together. The outer flowers are the ray florets and can be yellow, maroon, orange, or other colors, and are disinfected. The florets inside the circular head are called disc florets. The disc florets adult into what are conventionally called "sunflower seeds", but are actually the fruit (an achene) of the plant. The true seeds are encased in an unpalatable husk.

The florets within this cluster are arranged spirally. Typically each floret is oriented toward the next by roughly the golden angle, producing a pattern of interconnecting spirals where the number of left spirals and the number of right spirals are succeeding Fibonacci numbers. Typically, there are 34 spirals in 1 direction and 55 in the other; on a very large sunflower you may see 89 in one direction and 144 in the other.