Abstract

The effects of regenerant wastewater irrigation and high concentrations of Ca²⁺, K⁺, Mg²⁺ and Cl⁻ on growth and ion uptake of nine species of landscape plants were studied. Significant differences in chloride tolerance were detected among the species. Generally, the species that had greater uptake of chloride grew less than species that took up less amounts of chloride. Lace fern (Athyrium filix-femina Roth.) had the highest tissue chlorine (Cl) concentration and was the most affected. Hydrangea (Hydrangea macrophylla Ser.) also had high tissue Cl concentration, but showed no growth reduction. Its tolerance was attributable to a high tissue calcium (Ca) concentration. The data suggest that in the species tested, higher tissue Ca concentrations were positively correlated with plant tolerance to Cl. Overall, the CL⁻ concentration in the wastewater seems to be the factor most likely to create problems for the landscape plants. However, severe negative effects will probably be noticed only for very sensitive plant species, but it is important to determine this before applying regenerant irrigation water.