Moulds and other types of fungi are not always harmful in garden soil, but if they grow too numerous they will begin to damage your plants. Mould and fungus are normally introduced to garden soil through the addition of mulch and compost. If they become detrimental to the plants in your garden, you must destroy them or remove the soil that is infested.
If you notice mould and fungus in mulch or compost before you have mixed it in with the garden soil, remove it from the garden and place it in a small pile. Soak the pile with water and allow it to sit for several days. The water will fuel a composting reaction which heats the pile and kills the mould and fungus. You can use a thermometer to measure the temperature of the pile. It should reach at least 43.3 degrees Celsius (110 degrees Fahrenheit) before you return it to your garden. Before returning the mulch to the garden, make sure the mould and fungus have been killed. If you have a compost heap in your garden, you can use it instead of creating a new pile.
If the mulch has already been mixed in with your garden soil, removal is more difficult. You can attempt to remove the infested soil and place it in a composting pile, but if you remove too much soil you can damage your plants. You can also use a garden shovel or spade to mix the soil, killing the mould and fungus. Afterward soak the soil with water.
Mould and fungus are easier to prevent than to remove. Avoid using mulches or fresh wood content. Mold and fungus grow well near fresh wood. If you are using a mulch with wood in it, compost the mulch before applying it to your garden. During the compost process, mix in high nitrogen fertiliser to prevent the growth of fungus and mould.
Before adding mulch or compost to your garden, check to make sure moulds and fungus have not grown in it. If they have, form a watered pile to reheat the mulch or compost and kill the mould and fungus.
When you add the mulch and compost to your garden, only mix it into the top 5 cm (2 inches) of soil. This will provide the fertilisation benefits for your plants but is less likely to cause mould or fungus.
Soak the mulch and compost in water immediately after adding it to your garden. The water will keep the composting reactions going for a few days so that the mulch and compost cools slowly. Rapid cooling can kill microorganisms that prevent the growth of moulds and fungus.