Copper Toxicity in Woody Ornamentals

Abstract

Rhododendron obtusum Planch. 'Delaware Valley' (Delaware Valley Azalea), Buxus sempervirens L. (common boxwood) and Cotoneaster divaricata Rehd. and Wils. (spreading cotoneaster) grown in sand culture received a complete nutrient solution containing Cu concns ranging from 0.032 ppm to 100 ppm. Development of Cu toxicity symptoms were recorded for 8 weeks, then Cu, Fe, and Mn levels in roots, stems, and leaves were determined. Chronic Cu toxicity symptoms were interveinal chlorosis and stunted growth. Acute Cu toxicity caused wilting, desiccation, and death of all affected plants. Tissue Fe and Mn levels were not consistently correlated to the Cu concn of the treatment solution. Only tissue Cu levels proved useful as an index of Cu toxicity.