A great biological mystery over the past 100 years has to do with what induces plants to make flowers. Young angiosperms don't have flowers, they make just roots, shoots and leaves. But at some point during their lifetime, they begin to make flowers. The question is: what triggers this? A major clue in solving this mystery happened about 100 years ago when scientists discovered evidence for a flower-inducing signal, produced in the leaves, that they named florigen.
This book is a summary of what is currently known about the biology of florigen and flowering, written by someone who has been teaching the subject to college students for nearly 30 years. It's also a book about how and why plants tell time, because this is part of the story. And, just for fun, there's some speculation based on recent scientific evidence about the origin and diversification of flowering plants.