Passage A: Many introduced plants grow larger in their new range because specialist herbivores from their native range are absent. In exclusion experiments, protecting native-range plants from herbivores largely removes the growth difference between ranges. The author concludes that release from enemies is the main initial advantage. Passage B: Common-garden experiments using seeds from native and introduced populations show that introduced populations grow faster even when herbivores are absent and conditions are identical. The difference is strongest in populations introduced longest ago. The author argues that enemy release may matter early, but rapid evolutionary change can later increase growth.