Any additional stresses at that point can cause problems that are obvious. During the summer strong sunlight and long day lengths encourage vigorous new growth and problems are less noticeable. Last week we talked about the effects of various de-icing compounds, including road salt, on landscape plants. Well, houseplants can also be affected by salt. . If you use softened water for your houseplants, that water adds sodium to their diet, and to the soil.
Water softeners work by replacing the calcium and magnesium in the water, often with sodium.
Calcium and magnesium compounds are the components that make water hard, leading to lime deposits on plumbing and making it hard for soaps to develop a lather. They are important nutrients for plants though, and sodium is not. Softened water can also affect the soil structure for a potted plant, just as too much road salt can affect the soil structure of the nearby soil. The sodium compounds accumulate in the soil of the houseplant, and can cause problems for the plant. Different plants have different sensitivities to sodium itself, but sodium can also affect the soil.