2018 ASHS Annual Conference

A greenhouse study was conducted to assess the relative salt tolerance of 11 varieties of hydrangea: Hydrangea macrophylla ‘Ayesha’, ‘Emotion’, ‘Mathilda Gutges’, ‘Merritt’s Supreme’, and ‘Passion’, H. paniculata ‘Pink Diamond’ and ‘Quickfire’, H. quercifolia ‘Snowflake’, H. serrata ‘Preciosa’, H. serrata x macrophylla ‘Sabrina’ and ‘Selina’. Softwood cuttings received from a commercial company were rooted in a mist propagation bench. Seven weeks after propagation, rooted cuttings were transplanted to one-gallon containers filled with Metro-mix 360. Six weeks after transplanting, uniform plants were selected for experiment. Plants were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS∙m^-1 (control), or nutrient-solution based saline solutions at EC of 5.0 dS∙m^-1 (EC 5) or 10 dS∙m^-1 (EC 10) for eight weeks. Four weeks after treatment, ‘Quickfire’ plants in EC 10 exhibited severe salt damage with most of them dead. ‘Pink Diamond’ is the next sensitive cultivar showing salt damage in EC 10, while ‘Passion’ also showed some damage with lower yellow leaves. By the end of the eight week experiment, most ‘Quickfire’ were dead in both EC 5 and EC 10, while ‘Pink Diamond’, ‘Preciosa’, and ‘Passion’ had severe salt damage in EC 10. ‘Ayesha’ and ‘Sabrina’ did not have obvious visual salt damage. ‘Merritt’s Supreme’ and ‘Mathilda’ plants in EC 5 had minimum salt damage. Total shoot dry weight of all cultivars were significantly reduced compared to the control in the elevated salinity, except for ‘Selina’. A second experiment was conducted two weeks later than the first one using the same plant materials, that is, plants were two weeks old at the start of treatment compared to those in the first experiment. Both experiments indicated that ‘Ayesha’ and ‘Sabrina’ were relatively salt tolerant, ‘Selina, ‘Merritt’s Supreme’ and ‘Mathilda’ were moderately tolerant, ‘Emotion’ and ‘Snowflake’ were moderately sensitive, while ‘Quickfire’ was the most sensitive followed by ‘Pink Diamond’, ‘Preciosa’, and ‘Passion’.