Seed heads

Good to know

• The pattern of seeds on a sphere is called the Fibonacci lattice; it is also used to place sample points evenly over a globe or an image in computer graphics, because it spreads points very evenly with a single simple rule.
• Each dandelion seed hangs from a ring of fine hairs called a pappus, and in 2018 a team led by Cathal Cummins showed in Nature that the ring holds a separate ring of spinning air above it, a vortex that lets the seed stay aloft far longer than a solid parachute of that size.
• A dandelion head is not one flower but a hundred or more tiny flowers packed together, and each one becomes one seed; the "clock" is the whole head of seeds, each with its own parachute, waiting for a breath of wind.
• Dandelion seeds can travel kilometres on the wind, and far greater distances have been reported; the plant needs no insects to make a seed.
• The golden angle, about 137.5 degrees, is the turn that leaves the most even spacing however many seeds there are, because it is the angle that is hardest to approximate by a fraction: it is why sunflower seeds, pine cones and these heads show spirals in two directions at once.