Recent decades have seen major efforts to build databases on the distributions of native and alien species. Consequently, we now know that more than 16,000 vascular plant species have been recorded as naturalized alien species worldwide, several thousand of which are considered invasive. For alien plant, a major pathway of introduction is cultivation. A joint analysis of the first version of the World Cultivated Plants (WorldCuP) database and the Global Naturalized Alien Flora (GloNAF) database showed that global patterns of naturalization were largely explained by colonization pressure. Still, only a small proportion of the introduced species has become naturalized. Potential drivers of plant invasion success are global change factors such as climate change, eutrophication and pollution. In line with this we could show that many species that have become more common due to environmental change in their native European ranges are also expanding globally as naturalized aliens. Nevertheless, an analysis of the IUCN Red List identified 238 plant species that are threatened with extinction in their native regions but have become naturalized or invasive in other parts of the world, thereby posing interesting challenges for management. Although such macro-ecological analyses based on large databases provide major insights into potential drivers of large-scale plant-naturalization patterns and consequences, we need experiments to test the mechanisms that might give naturalized alien species an advantage over native species. In my group’s experimental work, we focus on how ecological processes that determine coexistence of plant species —particularly, competition and plant-soil feedback (i.e. the process in which plants change abiotic and biotic components of the soil, which then affects subsequent plants growing on that soil)— might be affected by various global change factors, and by the numbers of co-acting global change factors. For example, in a large experiment with five pairs of native and alien species and nine global change factors, we found that with increasing numbers of concurrent global change factors plant-soil feedback shifted from negative to neutral or positive in native species, whereas they were consistently positive and became stronger in alien species. This experiment and others suggest that many naturalized plant species take more advantage of (or suffer less from) increasing numbers of global change factors than native species do. Together, our experimental and macro-ecological studies indicate that with further global environmental change we can expect further big changes in our regional floras.