“Anecdotal evidence was that the hormone gibberellin promoted the switch to flower formation in short-lived plants, along with other cues such as temperature, season and photoperiod,” Wagner said. “But in the long-lived plants, like in fruit trees, people have known that if you sprayed them with the hormone it inhibited flower production. So it was a big puzzle: why would the same hormone do one thing in short-lived plants and another in long-lived plants?”