Reliable studies of biodiversity are dependent upon collection of specimens. Herbarium specimens form the basis of floristic and plant taxonomic work, and are also important to broader biological studies because they serve as aids to identification and vouchers, and they are the best indicators of changes in the flora. Even in the U.S., with a relatively well known flora, continued collecting is important because our flora is imperfectly known and new taxa continue to be described at high rates. Furthermore, rapid changes can occur to floras through extinction, local extirpation of species, and spread of invasive plants. It is imperative that the knowledge of U.S. flora be kept current to provide the baseline data needed to combat the biodiversity crisis and the spread of invasive plants. There is concern, however, that the rate of collecting is decreasing to the point that our biodiversity infrastructure is inadequate to provide sufficient knowledge to counter these contemporary crises. To determine if plant collecting in the U.S. is decreasing, we recorded rates of within-state plant collecting from about 50 representative herbaria. Collection rates by decade were accessed for nine exemplar genera: Amelanchier, Antennaria, Corallorhiza, Juniperus, Leersia, Nuphar, Phlox, Populus and Woodsia. The results indicate that each herbarium has a unique history and temporal distribution of collections, however, a few trends emerge from these data. Some peaks in collecting are associated with production of statewide or regional floras and special large-scale floristic projects. In general, these peaks overlay a pattern of decreasing collection over the last 30-40 years. These findings begin to document the nature of changes in specimen collecting; such information is prerequisite to discussions regarding the continued need for plant collecting in North America.

Key words: Herbaria collections, Plant collecting patterns in North America