Despite their recognised ecological value, relatively little is known about the nutritional value of species-rich rangelands for herbivores. In a recent study published in AoB PLANTS, Bumb et al. investigated the sources of variation in forage quality in plants from species-rich Mediterranean rangelands in southern France. Digestibility was affected by species growth form, harvest date, developmental stage and management regime, and differed between leaves, stems and reproductive parts. The dry matter content of the different plant parts, an estimate of the density of their tissues that is closely related to fibre content, emerged as a good predictor and an easily measured trait to estimate digestibility in the wide range of species encountered in their study.