Irrigating plants based on their water requirements enhances water use efficiency and conservation; however, current irrigation practices for container-grown greenhouse plants largely relies on growers' experiences, resulting in leaching and/or runoff of a large amount of water. To address water requirements of greenhouse-grown plants, this study adapted a canopy closure model and investigated actual evapotranspiration (ETA) of Calathea G. Mey. 'Silhouette' and Stromanthe sanguinea Sond. from

more »

... ansplanting to marketable sizes in a shaded greenhouse. The daily ETA per Calathea plant ranged from 3.55 mL to 59.39 mL with a mean cumulative ETA of 4.84 L during a 224 day growth period. The daily ETA of S. sanguinea varied from 7.87 mL to 97.27 mL per plant with a mean cumulative ETA of 6.81 L over a 231 day production period. The best fit models for predicting daily ETA of Calathea and Stromanthe were developed, which had correlation coefficients (r2) of 0.82 and 0.73, respectively. The success in modelling ETA of the two species suggested that the canopy closure model was suitable for quantifying water use of container-grown greenhouse plants. Applying the research-based ETA information in production could reduce water use and improve irrigation efficiency during Calathea and Stromanthe production.