Effects of soil pH, root density, and tree growth regulator treatments on pin oak chlorosis

Abstract

A relationship between chlorosis and soil pH or fine root development could not be established for pin oaks (Quercus palustris) growing on highly disturbed sites along streets and on a less disturbed golf course site. Regression coefficients were low (P ≤ 0.28) and not significant (P ≤ 0.58) in all cases. Soil injection of 0.8 g/cm paclobutrazol (PBZ) resulted in a significant increase in fine root density on yellow golf course trees compared to controls and significant greening on yellow street trees compared to untreated controls over a 4-year period. Root density was improved by PBZ treatment on the golf course site where the soil was generally better for root growth. The effect on color was most pronounced on street sites where chlorosis development and decline were progressing rapidly. Untreated green golf course trees did not develop chlorosis rapidly enough to show conclusively that the growth regulator treatment could help to stabilize the trees. Little color or root density improvement was expected from the treatments on healthy green trees.