*Helianthus annuus*. New World annual noted for its large flowering head.
The sunflower is an annual native to the Americas that is noted for its very large flowering head. It gets its names from these flowers which resemble a 'sun' image with a central disk and 'fiery' yellow petals. The common name is properly used to refer to Helianthus annuus although it has also been used for a number of other members of Helianthus genus.
Although the flowering head is usually referred to as a 'sunflower' or 'flower', it actually consists of over 1000 individual flowers sharing a common receptacle.
A well known property of sunflowers is that the flowers will track the sun during the day. This is not quite true: immature leaves and flower buds will track the sun from east to west during the day; but a mature flower head will not.
Sunflowers are used for decoration, food, bird food, and as a common source of cooking oil. Fibers from the stems can also be used in paper production. They were first domesticated in Mexico before 2600BC and later domesticated (or introduced from Mexico) in the Mississippi Valley.
Sunflowers are also used in soil cleanup applications, due to their ability to absorb heavy metals (including many problematic radio-isotopes) from the soil.
Use this tag for questions about all of the Helianthus species that are commonly known as 'sunflowers'.