Which flowering plant can also serve as a natural clock?

Sunflower

The sunflower is well known for its ability to rotate and follow the sun across the sky, a phenomenon known as heliotropism. This fascinating feature is only observed in young flowers; mature sunflowers face east and remain fixed. This orientation towards the sun allows young plants to maximize photosynthesis for rapid growth. The heliotropism of sunflowers has inspired the use of the plant as a natural way to track the sun's passage, acting as a plant-based sundial.