The 2011 ASHS Annual Conference

Water use is an essential component of ornamental plant production, yet relatively little is known about the volume of water required to maintain acceptable growth rates of nursery crops.  The objective of this study was to determine the daily water use (DWU) of Hydrangea macrophylla, and also investigate the effects of various environmental factors on DWU.  The DWU of two hydrangea cultivars, ‘Pia’ (compact) and ‘Fasan’ (large), was calculated by weighing plants with load cells before and after every irrigation event for 83 days.  There was little difference in DWU of the two cultivars, which ranged from 50-300 mL/plant.  Daily light integral (DLI) was the most important environmental factor affecting DWU, with DWU increasing with increasing DLI.  The combination of plant age, final leaf area, DLI and their interactions explained 83.2 and 90.8% of day-to-day variation in DWU of ‘Fasan’ and ‘Pia’, respectively.  Vapor pressure deficit and temperature explained only about 4 - 6.5% of DWU. The results suggest that growers may be able to determine the required irrigation volume for hydrangeas based on plant size and DLI. We hope to use these data to develop a simple tool to predict hydrangea water use based on environmental conditions.