The sunflower (Helianthus annuus) is an annual plant native to the Americas in the family Asteraceae.

What is usually called the flower is actually a head of numerous flowers crowded together. The florets within this cluster are arranged spirally. Typically each floret is oriented toward the next by approximately the golden angle, producing a pattern of interconnecting spirals where the number of left spirals and the number of right spirals are successive Fibonacci numbers.

At sunrise, the faces of most sunflowers are turned towards the east. Over the course of the day, they move to track the sun from east to west, while at night they return to an eastward orientation.