Plants tell time. Not the way we do – for example, it’s 3.40pm, time to pick up the kids. But like animals, plants can sense that winter is coming and it’s time to drop leaves.
A sunflower anticipates daybreak, much like a rooster does before starting to crow. At sunrise, sunflowers face east to greet the first rays and continue to move with the sun until it sets in the west. Overnight, the sunflower head swings back around so it faces east at dawn.
Dr Mike Haydon, a University of Melbourne plant scientist, says sunflowers only move until the flower bud opens. At that point they stop their daily dance and permanently face east. “This is where the controversy arises,” says Dr Haydon, from the School of BioSciences. “People say ‘my sunflowers don’t track the sun’. Well if they’re open sunflowers, then they don’t do that because that’s when they’ve stopped.”