As introduced plants spread across the world, botanists have documented their naturalizations through herbarium specimens and published reports that serve as primary sources for the study and management of biological invasions. Invasion lag time, attracting much attention from both theoretical and applied perspectives, is typically defined as the time between introduction and first reported naturalization. Delays in identifying naturalized specimens in herbaria and publication delays may be a major cause of long reported lag times, but such delays have rarely been quantified. The Hawaiian naturalized grass flora serves as a case study to examine these delays among 269 species introduced after European colonization. From herbarium data, we found the collection date of the fist naturalized specimen, when it was correctly identified, and compared these to the date of the first published naturalization report. There was an average delay of 27 years (median of 17 years) between the first naturalized herbarium specimen and its publication, although this delay has decreased among more recent naturalizations. Among this delay is the time needed for correct identification of specimens, which was an average of 18 years, but a median of 4 years, indicating that most grasses are quickly identified but some identifications required decades. These delays, when not accounted for, obscure actual temporal trends in invasions. It is also important to understand and account for these delays in order to better characterize the phenomena that contribute to reported lag times for biological invasions. Minimizing identification and publication delays in the future will be important for successful management and control of new invasions. Expanded investment in and support of taxonomic experts at biodiversity institutions is needed to reduce reporting delays for new naturalizations.

naturalization, grass, hawaii, invasive species, identification