How the lily blooms
The “lily white” has inspired centuries’ worth of rich poetry and art, but when it comes to the science of how and why those delicately curved petals burst from the bud, surprisingly little is known. Now, however, mathematics has revealed that differential growth and ruffling at the edges of each petal — not in the midrib, as commonly suggested — provide the force behind the lily’s bloom. The research, conducted at Harvard’s School of Engineering and Applied Sciences (SEAS), contradicts earlier theories regarding growth within the flower bud. The petals, in fact, behave like leaves. Published online in the journal Proceedings of the National Academy of Sciences, the findings characterize the blooming process using mathematical theory, observation, and experiment. “That differences in planar growth strains can lead to shape changes has been known for some time,” says principal investigator L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics at SEAS. “But showing...