Response of Five Hydrangea Species to Foliar Salt Spray

Abstract

Hydrangeas are popular seaside plants; however, other than in anecdotal reports, there are no studies measuring their relative tolerance to salt spray. We examined response of ten cultivars and one subspecies of Hydrangea representing five species to foliar-applied salt solutions to recommend selections for seaside landscapes. Objectives were to determine whether there are differences in responses to salt spray among cultivars and species, and to determine whether varying concentrations of sodium chloride differentially damaged the plants. Plants were treated with a full-strength (ion concentration approximate to seawater) salt solution, a half-strength salt solution, or a control of tap water. Plants were rated after seven once-weekly applications based on percentage necrotic leaf area, an aesthetically and physiologically important symptom of damage. Cultivars of Hydrangea macrophylla and Hydrangea serrata were more tolerant of full-strength salt spray than cultivars of H. paniculata, H. anomala and H. arborescens. At half strength but not full strength, H. anomala ssp. petiolaris was most tolerant. Hydrangea macrophylla and H. serrata were the second most tolerant of half-strength applications. Hydrangea macrophylla or Hydrangea serrata should be planted where maritime salt spray will occur.

Salt Tolerance of Hydrangea Plants Varied among Species and Cultivar within a Species

“…In this study, we applied treatment solution once a week with an approximately 20% leaching fraction. The trends of leachate EC in all treatments agreed with those in our previous studies [14,21].…”

“…For example, H. macrophylla 'Passion' showed poor performance, with severe foliar salt damage, high mortality and greater reductions in leaf area and shoot DW compared to other cultivars in the same species. In our previous study with H. macrophylla 'Smhmtau' and 'Smnhmsigma', plants were treated with the same saline solutions at an EC of 5.0 dS•m −1 or 10.0 dS•m −1 for 35 days; however, the leaf Na + and Cl − concentrations were higher than those observed in the current study [14]. The salt tolerance of plants largely varies among species and even among cultivars of the same species, as evidenced in the current study.…”

“…Briefly, 50 mL of RO water was applied to a randomly selected plant per cultivar per treatment approximately 15 min following irrigation, and the subsequent leachate was collected and EC and pH were measured using LaQua twin probes (Horiba, Japan). A visual score was adapted from Liu et al [14] and was based on a visual assessment of salt damage (foliar necrosis) on a scale of 0 to 5 (0 = dead, 1 = 80% damage, 2 = 60% damage, 3 = 40% damage, 4 = 20% damage, and 5 = 0% damage, approximately).…”

“…Growth reduction percentage is another important parameter used to evaluate relative salt tolerance among different cultivars of ornamental plants [2,3,14,16,21,24,25]. Miralles et al [2] reported a reduction in shoot DW of 73%, and leaf area of 68%, in H. macrophylla 'Leuchtfeurer', when irrigated with saline water at an EC of 5.65 dS•m −1 (leachate EC of around 10 dS•m −1 ) for 11 weeks, compared to control (irrigated with fresh water).…”

“…Hydrangeas are popular landscape plants in coastal areas. In order to aid in the selection for seaside planting, Conolly et al [14] conducted a study to quantify the responses of five hydrangea species to foliar salt spray with full (ion concentration approximate to seawater at 35 parts per thousand) or half-strength sodium chloride solution, in seven once-weekly applications. Based on percentage necrotic leaf area, they concluded that H. macrophylla and H. serrata were more tolerant to foliar salt spray than H. paniculata, H. anomala and H. arborescens, and could be planted where maritime salt spray occurs.…”