Herbarium Specimens as Sources of Phenological Data

Herbarium specimens, or historically collected pressed plant specimens, represent a unique and powerful source of phenological information. This chapter outlines the historical and evolving uses of herbarium specimens, their strengths and idiosyncrasies as sources of phenological data, as well as key conceptual and methodological considerations for their appropriate use in phenological research. Each specimen consists of a dried plant (or cutting) alongside documentation of the location and date on which it was collected. Thus, each specimen represents a snapshot of a plant’s phenological status in a specific time and location. These data span over 387 million records collected across thousands of species from every continent and have been collected from the year 1532 to the present day, providing an unparalleled combination of long-term, taxonomically diverse, and spatially extensive information. Recent advances in the digital transcription of these data have also dramatically increased the accessibility of these data and greatly facilitated their usage in the burgeoning study of macrophenology.