How do I mulch my garden? And what even is mulch? What should I use? These are all questions that cross the mind of a beginner gardener when given the advice to mulch. Here, we will look at how to mulch, what to use and why we mulch.
How to Mulch
Mulching is the simple practice of applying a layer of organic matter to the surface of your soil. This replicates the natural processes in nature, whereby leaves and other dead plant matter fall to the surface in the autumn. The practice of regularly mulching your garden and leaving the soil intact is called no dig or not till gardening.
To mulch a garden you need to try and cover the soil with organic matter. By covering the soil you help to create an insulating layer that traps evaporation, and is spongy on the surface. This means that it is easier to hoe so you can manage weeds, and water will absorb easier. Be careful not to mulch too deeply though. It’s better to do it annually, and apply about 1-2 inches than to apply 6 inches. The latter can interrupt the symbiosis between plants and the soil life.
What Should I Use to Mulch?
When we mulch, we use a form of organic matter that is already decomposed. This means that applying it to our soil does not create habitat for pests such as slugs and woodlice that can damage seedlings.
Compost, biodigestate or well-rotted manure is a good option. If you are using animal products such as manure be surre to check for Aminopyralid contamination first. You can do this by taking a pot of the compost and sowing a broad bean in it. If the plant looks normal and healthy, the manure is ok. If it looks twisted and curled, dispose of the compost somewhere other than you garden!
Why Mulch?
The benefits of mulching are enormous. The additional organic matter adds nutrients to the soil, helps it absorb water, reduces evaporation and helps control weeds. Let’s look at some of the amazing things that mulching does and why it works.
Mulching Improves Soil Structure
Worms are one of the most effective creatures when it comes to incorporating organic matter into your soil. In nature, organic matter falls to the surface of the soil in the form of dead leaves and twigs where it is then decomposed. Worms then eat the decomposing matter. They come to the surface of the soil to feed. On their way back down, they poop out what they don’t need in convenient little bundles of plant-available nutrients. Whilst they are moving up and down through the layers of the soil, they are also opening spaces called pores.
How Does Mulch Improve Soil Structure?
Earthworms aren’t the only thing in the soil being fed when mulching with organic matter. Good bacteria in the soil also feed on organic matter. They then excrete little sticky sugars called polysaccharides that hold together the tiniest particles in the soil. Fungi also feed on organic matter and hold together the soil with their delicate, root-like hyphae and another sticky substance called glomalin.
Far from causing the soil to become one solid, stuck-together mass, the action of all these things leads to soil with lots of pores. These are spaces through which air and water can travel into the soil, making the soil well-drained. Also, the particles that are stuck together form something called aggregates or peds – which hold onto water well. So the peds hold water, and the pores hold air.
When it rains, water filters through the pores and clings to the peds. This creates a vacuum in the pores, which in turn draws down more water, keeping it aerated at all times! The combination of pores and peds is what gives soil that highly desirable texture and is the perfect condition for our plant roots. This is why mulch is often said to help with both wet and dry soils, it improves the drainage whilst simultaneously creating a better ability to hold onto water.
Can Mulching Reduce Weeds?
In simple terms, mulching helps to provide a light barrier to seeds, which can suppress some weeds. A deeper mulch will do a more thorough job where this is concerned. But nothing will stop some weeds!
However, a good quality mulch will also improve your soil condition and bolster the soil ecosystem. A healthy soil ecosystem will regulate the number of Nitrates in your soil, which will, in turn, regulate weed growth. In unhealthy soil, nitrate concentrations will be high, but in well-balanced soil there will be nitrates and ammonium that help to produce strong, healthy growth and don’t allow weeds to take over.
A good mulch also provides us with a really nice soft surface for our beds. This is great for hoeing as it reduces resistance, meaning that we can easily stay on top of the weeds that we do have using a hoe.
How Does Mulching Feed Plants?
When applied as a mulch, organic matter feeds the life in the soil. This helps to get the less available nutrients out of the organic matter, particles and bedrock in the soil. Bacteria and fungi have the right chemical tools to extract nutrients and put them into plant-available form. But they need the carbon from the organic matter to fuel their activity. The plants feed the soil life with carbohydrates (a form of carbon), and the soil life feeds the plants with nutrients, meaning everyone gets a healthy, balanced diet.
Can mulching prevent pests and diseases?
Yes, it can, when used in combination with an organic and no dig approach. If you bolster the ecosystem in your soil, your “good guys” will outnumber the “bad guys”. The beneficial microbes in the soil congregate around the roots of the plant, forming a protective moat around the plant roots. The microbes want the plants to survive, so if a pest or pathogen crosses into this highly populated zone called the rhizosphere, it will have a difficult time getting to your plant. Not only that, but the life in the soil will send chemical signals to plants to bolster their defences.
Moreover, healthy plants that have a well-balanced diet with all the macro and micronutrients they need are much more capable of fighting off pests and diseases. This is because many of the phytochemicals they produce as protective compounds rely on tiny amounts of micronutrients that aren’t available in standard fertilisers. They are available in nutrient-rich mulch and in sediments in the soil, providing that the life in the soil is there to make it available to our plants.
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