Summer Irrigation of Established Oak Trees

Abstract

Two trials in California have shown that Valley oaks ( Quercus lobata ) are benefited by summer irrigation. In the first plot, 30 trees (± 125 years old) were near summer turf irrigation and 135 trees were not. In 1992, six years into a continuing drought, 28% of the non-irrigated trees were dead, while no trees near irrigation died. In a second plot, 11 of 12 irrigated trees had current year shoot growth of 5 to 31 cm, while only 2 of 12 non-irrigated trees showed similar results.