What to Do If Your Plant Grows Mold
Most plant lovers know how to manage yellowing or wilted leaves—usually the answer is more (or less) water. But what happens when you're dealing with a more complicated potted houseplant issue, like mold growth? "Plants growing mold on their leaves or soil are likely sending out a signal for help that they're getting too much water and/or not enough sun," explains Katie Dubow, plant expert and owner of Garden Media Group. While it might not seem like a big deal, it can be problematic for people with allergies or a hazard to your other plants. But don't panic just yet—there's an easy fix. Here's how to handle moldy houseplants, according to Dubow.
First, get rid of the existing mold.
Start by isolating your plant, since mold can quickly spread from one pot to another. Then, in a well-ventilated area, scrape away the top few inches of soil. If the mold is relatively new, that should do the trick. "If the mold is deeper than an inch or returns after a few weeks, you need to repot the plant entirely using an organic soil made for potted plants," says Dubow.
Before you repot the plant, clean the inside of the container with a squeeze of dish detergent, a sprinkle of baking soda, and water. The baking soda acts as a mild abrasive to scrape mold off the inside of the pot. Let the pot dry completely and then spray the infected leaves with water before wiping down each one with a paper towel (use a fresh towel for each leaf to prevent the spread of mold). Snip off any brown or dead leaves and toss them in the trash; spray the underside of those remaining with an organic fungicide. "You can easily make your own: Mix one tablespoon baking soda, a half teaspoon of liquid soap, a tablespoon of horticultural oil, and a gallon of water," says Dubow. "Don't skip the oil—it's what helps the mixture adhere to the mold." Let the soil dry completely before watering your plant again and keep your plant isolated for a few weeks to ensure the mold hasn't returned.
Prevent future mold growth.
Preventing pesky mold from creeping back requires setting a good foundation for your houseplants. "Start with a high quality potting soil; sometimes the soil that plants are growing in when you buy them isn't the best," says Dubow. "Repot them as soon as you get home and pay attention to their plant tag so you know how much water and light they need—it will keep them healthy. You can also mix a little cinnamon into the top of the soil, since it's a natural fungicide."
Only water plants when the soil is dry to the touch—and only water the soil, never the leaves of the plant (mold grows when a plant is constantly wet or siting in water). Also, every container should have drainage holes in the bottom; position the pot on a removable saucer to catch excess water, then remove that water 30 minutes after watering. Snip rotting leaves and stems from your plant often and make sure they have enough air circulation. Plants that can tolerate sun can be placed in a south-facing window, where they'll get bright sun all day.
Determine if your plant's mold is dangerous.
"A white colored mold on the surface of your soil is probably saprophyte, which is harmless to you and your family," says Dubow. "Powdery mildew on leaves is also not harmful to people or pets, but if you are extremely sensitive to mold or have an allergy, don't take any risks!"