2019 ASHS Annual Conference

Spirea (Spiraea sp.) plants are commonly used as landscape plants in the Intermountain area of the western United States including Utah. The salt tolerance of Spiraea betulifolia, S. japonica, S. media, S. nipponica, and S. thunbergii were evaluated in a greenhouse. Plants were watered with a fertilizer solution at an electrical conductivity (EC) of 1.2 dS·m^-1 (control) or saline solutions at an EC of 3.0 or 6.0 dS·m^-1 once a week for 8 weeks. Eight weeks after the start of treatment, all spirea plants survived when they were irrigated with a saline solution at an EC of 3.0 dS∙m^-1. At this treatment, all spirea species remained good or excellent visual quality with visual scores greater than 4 (0 = dead, 5 = excellent) with an exception of S. thunbergii that exhibited slight foliar salt damage with an average visual score of 3.8. When irrigated with a saline solution at an EC of 6.0 dS∙m^-1, S. thunbergii plants all died. S. media had severe foliar salt damage with an average visual score of 1.5, while S. betulifolia, S. japonica, and S. nipponica showed moderate foliar salt damage with visual scores around 3. On average, the shoot dry weight of all spirea species irrigated with saline solutions at EC of 3.0 and 6.0 dS∙m^-1 decreased by 19% and 48%, respectively. In conclusion, S. japonica, S. nipponica, and S. betulifolia were relatively more salt tolerant than S. media and S. thunbergii.