When Leaching is Good

If leaching makes you think of that annoying friend who always “forgets” his wallet, or that relative who overstays her welcome, readjust your thinking. For the purposes of this article, leaching refers to rinsing the soil of your houseplants.

Occasional leaching of your houseplants leads to lush, healthy growth of your indoor garden. Leaching provides the best way to prevent salt build-up, which can be harmful to plants. When salts build up to high levels in the soil, your houseplants can develop toxic salt syndrome, which can be deadly.

Salts accumulate in the soil to dangerous levels because of the overuse or eventual buildup of chemical fertilizers (one reason why I recommend organics), and tap water* can also add to the salt content of potting soil over time. Signs that a houseplant has salt buildup in the soil include a crusty white layer on the surface of the soil and around the drainage holes.

Plant reactions to salt buildup include reduced and smaller than average growth, dropping of lower leaves, brown leaf tips, dead root tips and wilting not caused by incorrect watering. Houseplants damaged by salt buildup are prone to pest and disease infestations.

To leach the soil in your houseplants, follow these steps:

1. Place the plant outdoors or in a sink or bathtub. 

2. Slowly pour warm water into the plant, making sure to make contact with every square inch of the soil. 

3. Let the water wash through the soil and drain out.

4. Aim for washing through the soil an amount of water that is the equivalent of at least twice the volume of the pot. So if your plant is in a half gallon pot, rinse the soil with at least a gallon of water.

5. If the plant is particularly susceptible to salt buildup, use a salt leaching solution in the water. Such products contain free-floating chelates that capture the salts as you water and flush them out of the soil.

6. If it rains and the weather is mild, rainwater is the best thing for leaching houseplants. Place plants outdoors and let the rain leach the soil, or if you catch and store rainwater, use it to leach your indoor garden. 

Avoid salt buildup by leaching your indoor plants every four to six months.

When the soluble salt level in your houseplant soil is particularly high, it’s often best to repot the plant and replace with fresh soil. For pots stained with salt buildup, scrub the buildup off with a stiff wire brush and rinse well. If you have difficulty removing the stain, try a baking soda, water and vinegar solution. And if the pot seems to be too far gone, replace it. 

 *Note: Never water houseplants with softened water, as this is extremely high in salts and will quickly lead to toxic salt buildup.