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What Causes Mold to Grow on Houseplants?

2 minute read

Click play to listen to What Causes Mold to Grow on Houseplants article.

Ever notice mold growing on your houseplants? While it’s not uncommon to find mold on a potted plant or on flowers that have been in the vase for too long, it’s not something most of us want around the house.

Thankfully, most common plant molds aren’t dangerous to humans. But they are unsightly, and the mold spores can become airborne and irritate allergies.

Let’s look at some common causes of mold on houseplants, and learn a few tips on how to prevent it.


If you find mold on the soil in a potted plant, that typically means you’re watering the plant too often and the soil is persistently moist. Keep in mind that most indoor plants require less water than outdoor plants, in part because they receive less sunlight to evaporate excess moisture.

Try watering your houseplants only when the soil is dry to the touch, and keep them in areas where they’ll receive moderate amounts of sunlight each day. During colder and darker times of the year, plants will need less water.

Poor Water Drainage

Another cause of soil that’s too wet is poor water drainage, which can come from a lack of drainage holes, incorrectly sized pots, and soil that’s too dense.

Most pre-mixed potting soils will include materials like peat moss to keep the soil from becoming too dense. To find the right pot, make sure it has drainage holes and consider the length and spread of the roots—the more roots are allowed to grow and thrive, the more water they can absorb.

Insufficient Air Circulation

Air movement helps dry out plants between waterings, which reduces the risk of mold growth. Certain areas of the home are prone to less air circulation, especially during months when windows and fans aren’t being used. If you keep plants in those types of areas, try adding some form of air circulation or move the plants to more central areas of the home.

Beyond the health of your plants, proper air circulation and ventilation are important for the well-being of you and your family. This is especially true in areas where moisture is consistently introduced, like the kitchen, bathroom, and laundry room. Check out AprilAire whole-home fresh air ventilators for more information.

Elevated Humidity Levels

Some plants do well in high-humidity areas, but many common houseplants will suffer from mold and stunted growth when kept in overly humid environments. The soil doesn’t get a chance to dry out, which can lead to mold. And growth is impacted when the plant doesn’t have the ability to evaporate water into the air or draw nutrients from the soil.

Excess humidity levels can cause mold issues all around the home. AprilAire recommends keeping the humidity level in your home between 40–60% for your own health and the health of your plants.

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