From overlooked to established: the case of Panicum gilvum (Poaceae) in the Netherlands

Recent floristic surveys, herbarium revisions and analyses of observations from the online citizen-science platform waarneming.nl, have revealed the widespread presence of Panicum gilvum in the Netherlands — a South African species previously overlooked and often misidentified as P. dichotomiflorum. Although morphologically similar to P. dichotomiflorum, P. gilvum differs, among others, by its usually prostrate to ascending growth habit, its barely exserted, smaller and relatively pauciflorous inflorescence, and often smaller, blunter spikelets. It is distinguished from P. schinzii by its sterile lower florets. The species was first correctly identified in continental Europe in 2024 at a grain transshipment site near Ghent, Belgium. However, subsequent fieldwork and a review of herbarium specimens and photographic records revealed that many earlier observations attributed to P. dichotomiflorum in Dutch maize fields actually referred to P. gilvum. Remarkably, specimens collected multiple times between 1938 and 1951 near a wool factory in Tilburg, previously misidentified, actually belong to P. gilvum; these early records appear to represent isolated wool alien plants, with no direct link to the recent naturalization in maize fields. Genetic analyses confirmed the identity of the Dutch P. gilvum specimens, showing a clear differentiation from P. dichotomiflorum as well as a close affinity with authentic South African material of P. gilvum. The earliest naturalised Dutch records date back to 2009, and thus suggest that the species had gone largely unrecognized until now. Panicum gilvum now appears to be naturalized in the Netherlands and is definitely more common in maize fields than P. dichotomiflorum. This paper discusses the diagnostic features distinguishing the three Dutch representatives of section Dichotomiflora, provides illustrations of key morphological traits, and reconstructs the likely introduction and naturalization history of P. gilvum in the Netherlands.