How flowers catch raindrops

Abstract

Several species of plants have raindrop-sized flowers that catch raindrops opportunistically in order to spread their 0.3-mm seeds distances of over 1 m. In the following fluid dynamics video, we show examples of these plants and some of the high speed videography used to visualize the splash dynamics responsible for raindrop-driven seed dispersal. Experiments were conducted on shape mimics of the plants' fruit bodies, fabricated using a 3D printer. Particular attention was paid to optimizing flower geometries and drop impact parameters to propel seeds the farthest distance. We find off-center impacts are the most effective for dispersing seeds. Such impacts amplify the raindrop's speed, encapsulate seeds within drops, and direct the seed trajectory at angles optimal for long-distance dispersal.