The Annual Sunflower is thought to be adventive from western United States. However, it was cultivated as a source of food by native Americans, and was likely introduced to Illinois by them prior to European settlement. The cultivated sunflower of modern agriculture is a self-pollinating hybrid of this plant and another annual sunflower that occurs in the Great Plains. Because of its large heart-shaped leaves, it is easy to distinguish the Annual Sunflower from other Helianthus spp. that occur in the Midwest.