The Heliotropism of a Sunflower

Identification

• Most sunflowers move their heads in relation to the sun, facing east in the morning and gradually moving as they day progresses to follow the sun's path across the sky. At dusk, the sunflower heads face west, but during the night they move to an eastern position once again.

Timing

• Sunflower buds exhibit heliotropism. Open flowers do not exhibit this tendency, but are typically frozen in an eastern orientation. Plant sunflowers in early summer, after the last frost. The plants grow quickly, producing flowers within 90 to 100 days, depending on growing conditions and variety.

Sunflower Characteristics

• In addition to heliotropism, sunflower plants have other interesting characteristics. The plants are native to the U.S. and were domesticated around 1,000 B.C. for use as a food and oil plant. Pollen producing sunflowers are used for their seeds, while non-pollen producing hybrids are valued as cut flowers. Sunflowers have allelopathic properties, meaning they suppress seed germination and growth in nearby plants.

More on Heliotropism

• Sunflowers are not the only plants to exhibit the phenomenon of heliotropism. Several plants growing in arctic climates use this mechanism to capture the sun's heat. Like sunflowers, now buttercups and arctic poppies follow the sun's path from east to west. This characteristic allows them to retain warmth up to 14 degrees higher than surrounding air temperatures. This activity contributes to their growth and survival and also attracts bees and other insects that do not have the ability to generate heat on their own.