Carpobrotusedulis(L.) N. E. Br., an exotic perennial that invades the coastal habitats of California, hybridizes with the presumed nativeCarpobrotuschilensis(Mol.) N. E. Br. To investigate the potential role of hybrids in the invasion process byC.edulis, we compared the growth and plasticity of clones of hybrids and parental species. Ramets of three hybrid classes and both parental species were grown in a common garden with four different environments. Both the parental species and the hybrids exhibited strong plastic responses to the test environments for characters describing clonal growth and physiology.Carpobrotusedulisconsistently had the largest biomass, butC.chilensisproduced longer branches. Carbon isotope ratios (<$QFD0E00000010446D80BFFEFF88A6750DA8D9C8282ADCC6210090483DA6ECD7658F80>13C) showed only weak differences among morphotypes. Hybrids were mostly intermediate relative to parental species in both growth and physiological characters. The intermediacy of hybrids in their response to environmental variation indicates that they do not have inferior growth compared with parental species. The high amount of plasticity of the hybrids andC.edulis, as well as their overall similarity, may account for their invasion success in different habitats of coastal California.