Water scarcity is a pressing issue in Utah and the Intermountain West, leading to a growing interest in exploring alternative water sources for landscape irrigation. However, alternative water often contains elevated levels of salts, such as sodium chloride (NaCl), which can negatively impact plant growth and appearance. This study investigated the effect of saline solutions on the aesthetic value, growth, and stomatal conductance of three ornamental species: Hibiscus syriacus ‘JWNWOOD4’ (Pink Chiffon® rose of sharon), Viburnum carlesii ‘Spiro’ (koreanspice viburnum), and Vitex agnus-castus ‘SWVACSD’ (lilac chastetree). Plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 0.9 dS·m-1 and saline solutions at 5.0 or 10.0 dS·m-1 for eight weeks. Visual quality was rated weekly using a reference scale ranging from 0 to 5 (0 = dead, 5 = excellent without foliar salt damage). Half of the plants per treatment per species were destructively harvested on 16 Aug (first harvest), and the remaining plants on 4 Sep (second harvest). Plant growth parameters and stomatal conductance were recorded at harvests. Foliar salt damage, such as leaf discoloration and necrosis, was prominently observed in plants, particularly in Viburnum carlesii subjected to elevated EC irrigation. Higher stomatal conductance was consistently observed in all plants irrigated with nutrient solution compared to those under saline irrigation. Interestingly, the salinity treatment did not significantly affect the growth of Vitex agnus-castus, indicating its high salt-tolerance. Notably, Viburnum carlesii displayed higher sensitivity to salinity stress compared to the other two ornamental species. These findings highlight significant variations in responses among the ornamental plant species under saline irrigation at varying EC levels, emphasizing the necessity of employing appropriate alternative water usage strategies.
