Soluble Salt Damage: The Secret Killer of House Plants

In the hands of some people, house plants race down the road to death as soon as they're brought home. Then there are other caretakers who can keep them alive for a few months only to watch a slow but steady decline. I suspect many of their house plants die of soluble salt damage. Brown leaf tips, not much new growth, new leaves that don't attain normal size, and loss of lower leaves all indicate salt damage, a problem few house plant owners ever hear about.

In the eight years I worked as a grower running a production greenhouse at a prominent public conservatory, I didn't worry much about soluble salt build up. We watered the plants with hoses and excess water ran freely through the drainage holes onto a gravel floor.

Dealing with my own house plants is a different story. Like most people, I keep saucers under my house plants and cover the plain growing containers with baskets or ornamental cachepots. When I water and fertilize, I know I'm also adding soluble salts, and I have to pay attention to keeping the build up under control.

Where do these salts come from? Soluble salts are dissolved minerals that occur naturally in tap water and the amount and identity of them varies from one geographic location to another. Fertilizer, while necessary to healthy house plants, also consists of soluble salts. If you have ever put water on the stove to boil and forgotten it to the point where it just boiled dry but didn't burn the pot, you may have seen a chalky residue in the pot. As the water evaporated, the natural salts were left behind. The same thing happens in your house plants.

Month after month, watering after watering, we add to the salt build up in our house plants until the small, sensitive feeder roots burn away from high salt concentration. These damaged roots can start to rot, or the house plant simply suffers from lack of an adequate root system.