AbstractThe impacts of invasive alien plant species on native plants are generally well documented, but little is known about the mechanisms underlying their impacts on crop growth. A better understanding of immediate as well as legacy effects and of direct and indirect impacts of invasive alien plant species is essential for an improved management of invaded cropland. We investigated howLantana camaraimpacts the growth of two subsistence crops (maize and cassava) through competition for resources, allelopathy and the indirect plant–plant interactions. We carried out two pot experiments using soils from invaded abandoned, invaded cultivated and non‐invaded cultivated crop fields. In the first experiment maize and cassava were grown alone or together withL. camaraand half of the pots were treated with activated carbon to suppress allelochemicals. The effect of the soil microbial community onL. camara—crop interactions was assessed in a second experiment using autoclaved soil with 5% of soil from the three soil types. We found thatL. camarareduced the growth of maize by 29%, but cassava was not affected. We did not find evidence of allelopathic effects ofL. camara. Inoculation of autoclaved soil with microorganisms from all soil types increased biomass of cassava and reduced the growth of maize. BecauseL. camaraonly caused impacts when growing simultaneously with maize, the results suggest that removal ofL. camarawill immediately mitigate its negative impacts on maize.