Differential Growth Response to Salt Stress Among Selected Ornamentals

Evaluation of salt tolerance in herbaceous perennials was performed with mature potted plants under greenhouse conditions. Six herbaceous perennial species were evaluated for their tolerance to aqueous solutions of various sodium chloride (NaCl) concentrations over a 21 day period by measuring growth, water transpiration, and leaf nutrient content. Potential exists for utilization of these species in somewhat challenging saline environments along roadsides and in urban landscapes. Species evaluated in a mature growth stage included Achemilla mollis, Nepeta x faassenii, Sedum acre, Thymus praecox, Phlox subulata and Solidago cutleri. On the basis of relative growth rate and water transpiration responses to NaCl (0–400 mM) treatments, groundcovers were grouped into three tolerance categories: highly sensitive to salt treatment (S. acre), those with intermediate sensitivity (A. mollis, N. x faassenii, T. praecox, and P. subulata), and those exhibiting tolerance (S. cutleri). Sodium content in leaf foliage of S. cutleri was about ten-fold lower than other groundcover species in the 200 mM NaCl treatment, consistent with greater tolerance to NaCl treatments in terms of transpiration, biomass accumulation, and retention of green foliage. Comparison of foliar nutrient levels among groundcover species and treatments suggested strong differential response to NaCl treatment, indicating that changes in nutrient levels over time may be a reasonable way to predict NaCl tolerance in groundcovers.