Pests, Diseases & Plant Problems

> View All Articles

Mould and fungi in potting mix and garden soil


July 28, 2022


Searles Gardening Team

Why do we find moulds & fungi in potting mix & garden soils?

Although not always visible, moulds (a type of fungi) are present in every gardening mix containing composted organic matter. Moulds are a sign of life, although they might not be one you want to look at, since they are usually not what most people would refer to as pretty. Many organic gardeners believe that "living soil" is the ideal environment for growth, and there is some proven science behind how these organisms benefit plant growth and health. If you’re interested in to learn more about fungi and their role in helping plants, read on for a few key facts ->

What do fungi do?

Fungi perform important functions within the soil in relation to nutrient cycling, disease suppression and water dynamics, all of which help plants become healthier and more vigorous. At Searles, we love fungi because they:

  • Decompose woody organic matter and convert nutrients into more accessible forms, meaning plants are more able to use the nutrients in the soil or potting mix.
  • Increase nutrient and water uptake.
  • Improve plant resilience.
  • Improve soil structure.

Why is composted organic matter in gardening & potting mixes?

Composted organic matter in the growing mixes provides excellent nutrients, minerals and structure for plants to flourish and at the same time acts like a food for beneficial fungi. This in turn helps to create better overall growing conditions for plants, maximising results for you with your plants.

Should I be worried about visible mould I can see in the mix?

Moulds are present in gardening mixes even when you can’t see them. Always follow the precautions noted on the bag, including wearing gloves, and a mask if dusty and wash your hands immediately after handling.

Can these “good fungi” cause possible problems for plant growth?

From a plant growth perspective, most fungi are beneficial to overall plant health & growth. A rare issue can be the mould growing significantly through the mix and causing the mix to repel water. This is unusual and could be rectified by removing any visible mould clumps, allowing the mix to dry out in a well-ventilated area, applying a re-wetting agent, or by re-potting into fresh growing media.

Next time you see something that looks like a type of fungi or mould in your garden, potted plants, or growing media you have purchased, you can feel good about helping to provide a brilliant growing environment for your plants.

It really is a brilliant bit of natural recycling, don’t you think?

If you're keen to know more about Fungi in soils, some further information is available via the links below ->