Symmetrical swirls

SYMMETRICAL SWIRLS Twirl a sunflower around in your fingers and the pattern at the center of the flower head looks the same from every side. This is because the sunflower head is radially symmetrical—the florets form two sets of spirals starting at the same point somewhere in the center of the flower, before turning in opposite directions, one clockwise and the other counterclockwise.

Radial symmetry appears throughout the plant world, from daisies to pine cones. The spirals follow a pattern known as the Fibonacci sequence, named after the Italian mathematician who discovered it. In this sequence, each number is the sum of the previous two. The pattern starts 1, 1, 2, 3, 5, 8, 13, 21, and so on. The reason why Fibonacci numbers are common in nature is because this is the best way to pack the most flowers, leaves, or seeds into a tight space. A sunflower head is made up of many tiny florets—the dark rods in the picture are opened florets, while those in the center are unopened ones. Each new floret grows at an angle to the previous one, leaving no gaps and maximizing its exposure to pollinators.