AbstractThis contribution provides better insights in the water relations and the physiological traits of four commercial poplar genotypes of different genetic background, 'Bakan', 'Oudenberg', 'Koster' and 'Grimminge'. The main continuous (nondestructive and providing continuous and automated data records) and discontinuous (destructive and not allowing automation) plant water status (PWS) indicators were monitored at a multigenotype, commercial‐scale short‐rotation coppice plantation in East‐Flanders (Belgium), and their relationships with the principal environmental variables were assessed. All measurements were performed during the entire 2016 growing season on the third year of the third rotation in multistemmed trees. The discontinuous PWS indicators were measured on 10 separate days with a different evaporative demand and soil water content, while the continuous PWS indicators were recorded from April to November. The genotypes responded differently to environmental drivers and to soil conditions, based on the PWS indicators, featuring a different water behaviour in relation to the level of isohydricity. Poplar genotypes 'Koster' and 'Bakan' showed the typical water‐conserving behaviour of isohydric species, while 'Grimminge' was more in line with the anisohydric ones. A principal component analysis showed that sap flow (Fs) was the most suitable PWS indicator. The Fs and therefore the sap flow‐based canopy transpiration (Ec) were tightly linked to the phenological stage of the trees as well as to vapour pressure deficit and photosynthetic photon flux density, based on relationships between Ec and environmental variables. A quantitative predictive model was developed to estimate the crop water requirements for specific genotypes, by calculating transpiration per unit of ground area with a few environmental variables, monitored with easy‐to‐handle sensors.