Many invasive plants can reproduce clonally, and clonal integration plays an important role in the growth and reproduction of invasive clonal plants. In nature, the spatial distribution of resources for plant growth and reproduction, including light, water, and mineral nutrients, is usually heterogeneous. However, limited information is available regarding the effects of clonal integration on interspecific interactions between invasive plants and their native congeners in heterogeneous environments. A controlled greenhouse experiment was conducted with the invasive plant Wedelia trilobata and its congeneric native plant W. chinensis to explore effects of clonal integration on interspecific interactions between them in heterogeneous light environments. Ramet pairs of W. trilobata and W. chinensis were grown singly or in mixture under heterogeneous light conditions, and the connections between the two ramets of the pair were maintained or severed to allow for or prevent clonal integration. Clonal integration promoted growth and reproduction in W. trilobata and W. chinensis, and W. trilobata benefited more from clonal integration than W. chinensis. Compared to planting of each species singly, planting of the two species in mixture had significant effects on leaf biomass of W. trilobata and root biomass of W. chinensis. There was a significant interaction effect of clonal integration and interspecific interactions on total biomass and leaf biomass of W. trilobata, but not on the growth traits of W. chinensis. Clonal integration had significant effects on the interspecific interactions between W. trilobata and W. chinensis. These results indicate that clonal integration can alter some growth traits and interspecific interactions between the invasive plant W. trilobata and the native plant W. chinensis in heterogeneous environments.