Irrigation effects on the growth of newly planted oaks (Quercus spp.)

Abstract

The effect irrigation on the growth of container-grown oaks was investigated over a 4-year period. Quercus lobata, Q. agrifolia, and Q. douglasii were irrigated at three levels of reference evapotranspiration (0, 0.25, and 0.5 ET0) after being established for 1 year at the University of California Bay Area Research and Extension Center in Santa Clara, California, U.S. Although no significant differences were found in trunk diameter growth for irrigation treatments after 4 years, growth of Q. agrifolia was significantly greater than Q. lobata and Q. douglasii. Root mass, shoot mass, and root distribution were measured for Q. agrifolia, and mean shoot:root ratio was found to be 2.6 to 1. Many roots of Q. agrifolia were found to develop with a stronger vertical than horizontal orientation, and root distribution was not significantly affected by irrigation treatment. © 2005 International Society of Arboriculture.