A goal of comparative physiology is to understand underlying causes of the tremendous diversity of land plant form and function. The hope is that functional diversity of land plants can be distilled to a few traits that together capture the essence of plant form and function (Díaz et al., 2016), thereby simplifying plant diversity into a tractable number of fundamental ecophysiological ‘strategies’ (or plant functional types). However, there has been disagreement and uncertainty as to (1) which traits should make the shortlist – that is what the key dimensions of trait covariation are, and (2) whether broad‐scale trait patterns and the inferred functional tradeoffs hold at smaller scales relevant to predicting species responses to global change (e.g. whether between species trait patterns hold within individual species). In this issue of New Phytologist, the article by Rosas et al. (pp. 632–646) is a thought‐provoking article that investigates within‐ and among‐species variation in key plant traits along a water availability gradient in two major plant families from a European forest.