Mushrooms are the visible reproductive structures, or fruiting bodies, of an extensive underground network called mycelium. This network lives by breaking down organic matter like old tree roots, buried wood, or thick layers of thatch. Fungi produce these temporary growths when conditions align: high moisture, suitable temperatures, and a substantial food source. Their appearance often signals healthy soil, but their removal will not eliminate the fungal network.
Physical Removal of Visible Growth
The immediate solution is to physically remove the visible growth before it releases spores. This action is purely cosmetic and mitigates the risk of pets or children ingesting potentially toxic varieties. Removing the caps as soon as they appear prevents the dispersal of microscopic spores, which can spread the fungus to new areas of the yard.
You can remove the mushrooms by hand, mowing, or raking, but capturing the debris is important. When hand-picking, wear gloves and place the mushrooms directly into a sealed plastic bag for disposal in the trash, not the compost bin. If mowing, collect the clippings immediately to avoid spreading spores across the lawn. This physical removal does not affect the subterranean mycelium, which will produce new fruiting bodies if environmental conditions remain favorable.
Eliminating the Environmental Conditions
Long-term control requires changing the environment by reducing the three conditions fungi require: moisture, organic matter, and shade. The most effective method involves correcting poor soil drainage and managing moisture levels. Adjusting irrigation to water deeply but less frequently allows the soil surface to dry out between watering sessions. Watering early in the morning is also beneficial, as it prevents the prolonged surface moisture that fungi favor.
Improving drainage requires aerating the lawn, which reduces soil compaction and increases air circulation. This allows water to penetrate the ground more effectively rather than pooling on the surface. Removing excess thatch—the layer of dead and decaying organic matter—eliminates a food source that also traps moisture. Dethatching should be done when the layer exceeds half an inch in thickness.
Addressing the food source is a major step in suppressing fungal growth, as the mycelium feeds on decaying organic debris. Old tree stumps, buried construction scraps, or large dead tree roots are common culprits that can feed a fungal network for years. Removing large pieces of buried wood by digging them out is often necessary for permanent control in a localized area.
Regularly removing surface organic matter starves the fungus and limits its ability to spread. This includes:
- Raking up fallen leaves.
- Removing grass clippings.
- Clearing old, matted mulch.
- Cleaning up pet waste immediately, as it sustains fungal growth.
Increasing the amount of direct sunlight the area receives helps dry the soil surface quickly. Trimming back overhanging tree branches or dense shrubs increases light exposure, creating a less hospitable environment for fungi.
Chemical and Natural Suppression Methods
If environmental controls are insufficient, applying a substance to suppress mushroom growth is an option. Commercial fungicides are generally only effective against the visible fruiting body, not the entire underground mycelium. These products are available as contact fungicides, which prevent spore penetration, or systemic fungicides, which are absorbed by the plant. Broad-spectrum fungicides are often chosen when the specific type of fungus is unknown.
For a less aggressive approach, various household items can be mixed into a solution and applied directly to the mushrooms and surrounding soil. A simple mixture of water with a few drops of dish soap can be poured into the ground where the mushroom was removed, acting as a mild, localized suppressant. Similarly, a solution of one tablespoon of baking soda mixed into a gallon of water can be sprayed over affected areas, which helps by altering the surface pH.
A diluted white vinegar solution (four parts water to one part vinegar) kills mushrooms on contact due to its acetic acid content. Natural oils, such as neem oil, can also act as an effective fungicide by preventing spore germination. Exercise caution with any application, particularly vinegar and commercial chemicals, as they can potentially harm the grass or other nearby plants. Always follow product instructions closely and ensure children and pets are kept away from treated areas.