Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Ricinus is an invasive species. We assessed its responses to intra-and interspecific competition, and different intensities and spectral qualities of light. To evaluate resource portioning, we obtained biomass measurements of juveniles in different densities of co-specifics and another species; we also compared the proportion of juveniles to determine if there is recruitment limitation. We obtained the same information for juveniles growing in different photosynthetic photon flux densities (PPFD) and ratios of red to far-red wavelengths (R/FR). Competition and light did not limit recruitment, resulting in differences in biomass allocation only. Biomass decreased more for plants subjected to interspecific competition than to intraspecific competition, suggesting that Ricinus is both a poor intra-and interspecific competitor. Juveniles growing under reduced PPFD and R/FR differed in biomass allocation and morphology as do shade-intolerant species subjected to shading. Our results show that Ricinus presents high plasticity, which may contribute to its invasion ability.492263279Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [03/11123-4]