Mushrooms require specific growing conditions, and they surprise homeowners when they find them in houseplants. Treating houseplant mushrooms with fungicide is one of a handful of options. If you are considering this method, consider the cost, materials needed and likely success rate.
Types of Fungicide
Copper fungicide and neem oil are two fungicides that can be used on houseplants. They are sold in concentrates and, as of 2010, cost between $10 and $20. The concentrates are diluted and applied with a spray bottle to coat all plant and soil surfaces.
The mushroom common in houseplants, Leucocoprinus birnbaumii, is bright yellow and fades as the cap opens. They grow 1 to 3 inches tall with slightly smaller caps. Mushrooms with wide-open caps have or are preparing to spread their spores and create more mushrooms.
Mushrooms do not hurt houseplants. If left they will go through their normal life cycle. When the cap and stalk die back, they turn into a thread beneath the soil called a mycelium. A mycelium breaks down dead organic matter in the soil. This is good for your plant.
Leucocoprinus birnbaumii can be handled safely, but it is poisonous if eaten by people or animals. Identifying mushrooms is best reserved for professionals.
Success of Fungicide Sprays
You can use fungicide sprays to kill visible mushrooms, but they won't rid houseplants of them permanently. Mushrooms grow from spores that travel through the air. The spores exist in potting soil before it is purchased and thrive in its rich organic matter and warm temperatures. Topical fungicide treatments are most beneficial when used in conjunction with other controls.
Remove mushrooms with a plastic bag and capture a handful of soil beneath them. If mushrooms reoccur frequently, add a teaspoon of lime to the top of the soil to lower its acidity. As a last resort take the plant out of the pot and shake the bulk of the soil off the roots. Clean the pot with a 10-percent bleach solution and let air dry. Pot plant with fresh potting soil.
Adjust the plant's watering schedule so that you are adding more less often. Inspect the drain hole on the pot to make sure nothing is blocking it. Moving the pot to an area with better air circulation will prevent the soil from staying damp over long periods of time.