Effects of clonal integration on growth and reproduction of plants in heterogeneous environments have been extensively studied, but relatively little is known about the roles of clonal integration in homogeneous, stressful environments. We conducted a greenhouse experiment to investigate the effects of clonal integration on the stoloniferous invasive plant Alternanthera philoxeroides (alligator weed) under homogeneous, stressful environments, i.e., under simulated acid rain and herbivory. There were three levels of acid rain treatments , three levels of herbivory and two levels of clonal integration (no integration-stolon connection was severed; with integration-stolon connection was intact). In the control (i.e., no acid rain and no herbivory), severing stolon did not affect biomass or biomass allocation of alligator weed, but increased total stolon length, number of ramets and number of leaves. The simulated acid rain treatments did not affect biomass of alligator weed, no matter whether the stolons were intact or severed. When the stolons were left intact, the mild acid rain treatment (pH=4.5) markedly increased total stolons length and number of ramets, suggesting that mild acid rain may improve plant growth. Meanwhile, the acid rain treatments significantly affected biomass allocation to roots and stolons. Under mild acid rain treatment (pH=4.5) biomass allocation to stolons increased significantly, whereas that to roots decreased; however, severe acid rain (pH=3.5) did not affect biomass allocation of alligator weed. When the stolons were severed, the acid rain treatments did not affect growth or biomass allocation of alligator weed. The results suggest that alligator weed can well adapt to acid rain stress and clonal integration play a limited role under acid rain stress. When the stolons were left intact, the simulated herbivory treatments markedly affected biomass and number of leaves of alligator weed, but did not affect total stolon length or number of ramets. With increasing herbivory levels, biomass of alligator weed significantly decreased, but number of leaves increased. When the stolons were severed, effects of the herbivory treatments on biomass, total stolon length and number of leaves were the same as those in the intact clonal fragments. Therefore, despite the status of the stolons, the simulated herbivory treatments markedly decreased growth of alligator weed. The herbivory treatments also modified biomass allocation of alligator weed. With increasing herbivory levels, biomass allocation to leaves significantly increased and that to stolons and roots significantly decreased. The results suggest that alligator weed can also well adapt to herbivory stress and clonal integration also plays a limited role under herbivory stress. These features of alligator weed may be helpful for it to invade into new habitats, and clonal integration plays a limited role under homogeneous stressful, environments.