In this review, I discuss, and partly challenge, a number of paradigms, assumptions and definitions that apply to many fields of plant ecology. The main points include the need for a distinction between a growth- or yield-oriented versus a fitness- or biodiversity-oriented concept of limitation and stress, and the challenges of a meaningful handling of plant traits and their functional significance. Further, I discuss the central role of biological variation in plant ecology, including the various forms of adaptive adjustments, and the task of scaling plant responses in space and time. I close this review with a critical comment on data stratification in the analysis of large biological datasets (e.g. meta-analysis).