Estimating Water Needs of Landscape Palms in Mediterranean Climates

ADDITIONAL INDEX WORDS. evapotranspiration, irrigation, leaf production, plant growth, visual quality SUMMARY. The responses of five landscape palm species [king palm (Archontophoenix cunninghamiana), mediterranean fan palm (Chamaerops humilis), queen palm (Syagrus romanzoffiana), chinese windmill palm (Trachycarpus fortunei), and california fan palm (Washingtonia filifera)] to three levels of irrigation [50%, 25%, and 0% (no irrigation) of reference evapotranspiration] were evaluated in a coastal mediterranean climate in Irvine, CA. Cumulative leaf production varied greatly among the species, but only king and chinese windmill palms produced more leaves with additional irrigation. All species maintained at least minimally acceptable visual quality at the no-irrigation treatment. Mediterranean fan and california fan palms expressed near optimum performance with no irrigation. Many established landscape palms can maintain at least minimally acceptable appearance for an extended period with little or no supplemental water in coastal mediterranean climates. However, when rainfall plus irrigation is less than 50% of reference evapotranspiration, sensitive landscape palms could be expected to appear less attractive and grow less. Responses of palm species in this study were similar to those of many other landscape tree and shrub species, but the water needs of landscape palms are considerably less than those of commercial date palm (Phoenix dactylifera), oil palm (Elaeis guineensis), or coconut palm (Cocos nucifera).