It is rare in biology that a single trait can answer questions spanning several fields of research. One such trait is plant biology’s “leaf mass per area,” a simple measurement calculated by weighing a dried leaf and dividing by its original fresh area. Leaf mass per area, or LMA, which has been measured in thousands of studies, is used in nearly every field of plant biology to make predictions of many processes and properties such as leaf photosynthetic rates, nitrogen content and plant environmental preferences.