Dandelions are widely distributed in temperate regions around the world, and the success of these perennial plants in such vast areas can be attributed to their light and floaty seeds that can be carried far by the wind with just a gentle breeze.

According to recent research, while most dandelion seeds typically fall within a range of two meters from the plant, they can travel several tens of kilometers or even over a hundred kilometers under favorable conditions. But what enables them to fly such long distances?

Many of us have blown dandelions and admired the sight of their seeds gracefully floating in the air. When we think about why they can flow so quickly, most might instinctively attribute it to their lightweight and low density. While lightness is indeed crucial, it seems there are other secrets to their flight.

A recent paper published in Nature, titled "A separated vortex ring underlies the flight of the dandelion," unveils the flight mechanism of dandelion seeds. Through studying the physics behind dandelion seed flight, the authors reported the discovery of a new fluid behavior surrounding the immersed body.

Dandelions utilize pappus (fine hairs) to aid in seed dispersal. The pappus slows down the seed's descent, allowing it to travel farther than the distance carried by horizontal winds. Additionally, the pappus might influence the direction of seed descent. However, it's not yet clear why feathery seeds (like those of dandelions) have pappus instead of membranous wings, which are known to enhance lift in some other species.

Researchers from the University of Edinburgh, including Shinmei Nakayama and Ignazio Maria Viola, constructed a vertical wind tunnel to visualize the flow around freely flying and fixed dandelion seeds. Through long-exposure photography and high-speed imaging, the authors discovered a stable air bubble—a vortex ring—that separates from the seed but remains steadily positioned a fixed distance from the tip of the pappus.

Moreover, the porosity of the dandelion pappus seems to be precisely controlled to stabilize the vortex ring, and the drag per unit area generated by the pappus is over four times higher than that produced by a solid disk. This design enables feather-like structures to disperse lightweight seeds more effectively than membranous wings.

Interestingly, this structure is not exclusive to dandelions in nature. Many small insects' wings also employ a similar principle for flight. For example, the wings of a certain thrips species (Thrips ) have a similar structure, utilizing only 10% of the weight of a dense airfoil but producing 90% of the drag. Additionally, larvae of some aquatic insects (such as black flies) also employ similar mechanisms to propel their movement.