Abstract Flexible vegetation is deflected by fluid flow, reducing drag forces and thus inducing complex feedbacks which affect scalar transport, sediment mobility and biogeochemical cycling. However, we presently lack mathematical models for this disturbance, for all but the simplest plant forms. Studying pinnate stems, we introduce a dimensionless quantity, isoanemeity, which describes how foliage contributes to the phenomenon of flow‐induced reconfiguration. Structural deformations are simulated to study leafy stem reconfiguration, and isoanemeity is shown to delineate different types of streamlining behavior. We examine a range of cases from the literature, showing that isoanemeity can provide a quantitative tool for model design of foliated flows, especially applicable to aquatic environments. Further, we hypothesize that isoanemeity may be valuable in investigating plants of greater complexity, such as densely branched terrestrial vegetation.