The Sound a Tomato Flower Needs to Open

Stephen Buchmann gave the technique its name in 1983: buzz pollination, or sonication, the trick a bumblebee uses on a flower whose pollen refuses to fall out. About 8% of flowering plants — roughly 20,000 species, including tomatoes, blueberries, cranberries, eggplants and most kiwifruit — hide their pollen inside narrow tube-shaped anthers with a single small pore at the tip. Tilt the flower upside down and shake. Nothing happens.

A bumblebee lands, clamps the anther between her mandibles, curls her body around it, and decouples her flight muscles from her wings. Then she fires those muscles anyway. The thorax vibrates, the anther vibrates with it, and pollen sprays out the pore in a pale cloud. Callin Switzer, recording bumblebees at Harvard's Arnold Arboretum in 2013, clocked the average buzz at about 270 Hz — close to the C-sharp above middle C on a piano.

Honeybees cannot do this. Apis mellifera, the workhorse of American agriculture, lacks whatever neuromuscular trick lets a bumblebee uncouple and rev. Why is still not fully understood. The practical effect is that the most common pollinator on the continent is useless on a tomato flower, and commercial tomato greenhouses have to import their own bees. The standard rate is up to 50 Bombus terrestris colonies per hectare; the global trade is built on a Belgian veterinarian who figured out how to ship them in cardboard boxes in the late 1980s.

The flowers, for their part, get something out of the deal. By locking pollen behind a frequency gate, they hand it only to insects strong enough to be worth the metabolic cost — and refuse it to everyone else.