Optimizing mowing strategies for controlling Lupinus polyphyllus Lindl. in roadside habitats

Abstract Introduction Road verges provide refuge habitats for semi‐natural grassland species but can also facilitate the spread of invasive alien plant species such as Lupinus polyphyllus Lindl., which negatively impacts biodiversity. Objectives We studied how different mowing regimes affect L. polyphyllus performance, species richness, and plant community composition. Methods A factorial combination of mowing heights (10 or 30 cm) and mowing frequencies (two or three times per year) was applied to permanent plots along six road verges in Sweden over 3 years. Results Mowing height had a larger effect than mowing frequency on L. polyphyllus . Plots mown at 10 cm showed significantly lower lupine biomass (treatment years 2 and 3) and re‐flowering (only tested in treatment year 3) than plots mown at 30 cm. In treatment year 1, mowing had no effect at all. No further reduction of lupine biomass was found from treatment year 2 to 3. Effects of treatments on species diversity were small. While community composition differed between plots with and without lupine at the onset of the study, the mowing treatments did not affect community composition. Conclusions Mowing at a height of 10 cm may potentially enhance biodiversity by significantly reducing L. polyphyllus biomass. However, considerable variation in treatment efficiency among sites indicates that local abiotic conditions need to be considered when planning mowing regimes.