Herbarium specimens capture variation across spatial, temporal, and taxonomic scales. In the “extended herbarium specimen” concept, researchers have developed creative approaches to utilize specimens and their metadata. Recent work has used nondestructive, indirect approaches, such as reflectance spectroscopy, to obtain leaf reflectance spectra and estimate functional traits from pressed leaves. However, these models have focused on using recently collected specimens from temperate lineages. Here, we present our workflow for obtaining leaf-level reflectance spectra from herbarium specimens, highlight some challenges of working with spectra obtained from herbarium specimens, and insights learned about trait evolution in Polygonaceae. Polygonaceae is a compelling system to test hypotheses about repeated evolutionary trajectories in spectral and spectra-derived traits associated with ecological function. This group includes at least two major transitions to xerophytic (arid-adapted) lineages from wet-tropical lineages, including the radiation of iconic North American eriogonoids. This group also includes a diversity of habits and life histories, all with flat leaves that are amenable to the measurement of leaf reflectance. We obtained reflectance spectra from herbarium specimens, and plan to predict functional traits associated with leaf construction and nutrient content using previously constructed universal prediction models. We will model both the evolution of predicted traits and reflectance spectra, and use phylogenetic comparative methods to ask whether independently evolving xerophytic lineages converge in similar functional and spectral trait spaces.