Growth of Containerized Landscape Plants Is Influenced by Herbicides Residues in Irrigation Water

Abstract

Herbicides play an important role in the production of nursery crops by reducing weed problems and improving production efficiency. Herbicides applied to nursery crops may move in runoff water into retention basins, which are used to irrigate container plants. Studies investigated the growth and development of containerized landscape plants subjected to irrigation water containing herbicide residues. Containerized dwarf gardenia, Snow azalea, Buccaneer azalea, Hellers Japanese holly, fountain grass, and daylily were grown in fine pine bark medium in the greenhouse and were irrigated with water containing 1 mg/L and 10 mg/L of oryzalin, oxyfluorfen, and isoxaben. Fountain grass and daylily were the most sensitive to herbicide application with reduced root and shoot growth. Oryzalin was the most phytotoxic to fountain grass followed by oxyfluorfen and isoxaben. Oryzalin and oxyfluorfen at 10 mg/L reduced the growth index of fountain grass. Oryzalin was the most phytotoxic herbicide to daylily, followed by isoxaben and oxyfluorfen. Only the high rate (10 mg/L) of oryzalin reduced the growth index of daylily. Among woody species, the root weights of Hellers holly were reduced by 10 mg/L of isoxaben. The growth of other woody species was not affected by the herbicides.