During the day, the side of the sunflower stem facing east grows more than the side of the stem facing west.
That causes the tip of the plant (also called the apex) and therefore the flower to move gradually from the east side (the rising sun) in the morning towards the west side (sunset) in the evening.
Why do sunflower heads face east?
This property of facing the sun is mostly observed in young flowerheads and generally stops once the flower starts to bloom (mature sunflowers generally face east). The fascinating phenomenon of flowers following the sun across the sky is called heliotropism. The sunflower plant contains hormones called auxins.
What do sunflowers do at night?
At night, in its absence, the sunflowers face east again, anticipating the sun’s return. They do this until they get old, when they stop moving. It’s heliotropism, and sunflowers are not the only plants that track the sun.
What do sunflowers do on cloudy days?
A new study shows sunflowers have an internal clock and face east to keep bees and other insects happy. During the growing season, the young sunflowers rotate their bright yellow heads during the day to track the sun’s movement across the sky. They reset overnight, swinging their face back to the east.
How does a sunflower move?
In early morning, plant cells on the western side of the stem begin to grow and elongate, causing the sunflower bloom to tilt toward the sun. As the sun moves across the sky, the cells on the stem’s side that is opposite the sun elongate, keeping the flower head facing the sun.