BackgroundTo understand how local ecological knowledge changes and adapts, here in the case of the recent introduction of plant species, we report the knowledge and perceptions of the Ndjuka (Maroon) of French Guiana concerning two tree species,Acacia mangiumandniaouli(Melaleuca quinquenervia), which are categorized as “invasive alien plants” in the savannas of their territory.MethodsTo this end, semi-structured interviews were conducted between April and July 2022, using a pre-designed questionnaire, plant samples and photographs. The uses, local ecological knowledge, and representations of these species were surveyed among populations of Maroon origin in western French Guiana. All responses to closed questions collected during the field survey were compiled into an Excel spreadsheet in order to perform quantitative analyses, including the calculation of use reports (URs).ResultsIt appears that the local populations have integrated these two plant species, which are named, used and even traded, into their knowledge systems. On the other hand, neither foreignness nor invasiveness seem to be relevant concepts in the perspective of the informants. The usefulness of these plants is the determining factor of their integration into the Ndjuka medicinal flora, thus resulting in the adaptation of their local ecological knowledge.ConclusionIn addition to highlighting the need for the integration of the discourse of local stakeholders into the management of "invasive alien species,” this study also allows us to observe the forms of adaptation that are set in motion by the arrival of a new species, particularly within populations that are themselves the result of recent migrations. Our results furthermore indicate that such adaptations of local ecological knowledge can occur very quickly.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13002-023-00602-7.