Many tropical plants have the remarkable developmental trait of delayed greening, in which fast expanding young leaves appear white or pink, and do no net photosynthesis. This initially appears maladaptive, as the "job" of a leaf is to do photosynthesis, however, we showed that delayed greening is actually an effective defense. The input of chlorophyll, light harvesting proteins and photosynthetic enzymes are delayed until the leaf is fully expanded and protected by toughness. The resulting low levels of nitrogen and energy mean that leaves with delayed greening loose fewer resources for a given amount of herbivory. This benefit outweighs the costs of forfeited photosynthesis under conditions of very low light (low cost) and very high herbivory (high benefit). However, these precise conditions are only met in the dark understory of tropical forests, and this is also the only place where one finds species with delayed greening.