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How mulching helps the soil?

We all know what mulch is but, did you know there are a lot of different types of mulches? Here is a summary and some tips to ensure the best results in your garden.

Why you should mulch your garden?

There are four important reasons to mulch:

  1. Water conservation. Mulch stops the top of the soil drying out, keeps the soil moist, and can reduce watering by about 60 per cent.
  2. Prevents weeds and weed seed germination
  3. Keeps the soil temperature constant
  4. Organic mulch adds extra organic matter to the soil

What are the different types of mulch?

Mulch can be split into two categories: organic and non-organic. Organic mulch breaks down and adds organic matter to the soil. Here are the different types of mulch you can get, split by organic and non-organic.

Organic mulch, grass cuttings, straw mulch, woodchips and dried leaves


Grass Cuttings

It is best to use grass clippings as mulch in more remote areas of your garden to suppress weeds. They are high in water content and will decompose very quickly. However, the high water content can turn them slimy and have an unpleasant smell. This in turn causes them to getting matted and not allow water to pass through into the soil. Only use grass clippings as mulch if you have not used any weed killer or synthetic lawn care products on your lawn – these can be bad for some flowers. You can use untreated grass clippings as mulch for open, unplanted areas or in the compost bin

Hay or Straw

One of the most popular types of mulch that can be bought from any gardening centre. The benefit of using straw is it becomes softer when it gets wet and it also works as a great soil conditioner.

Straw decomposes very slowly so you won’t have to keep topping this up. It is more popular for vegetable gardens as it is high in nitrogen – really useful for fast growing annuals such as tomatoes and root vegetables. One more benefit to using straw as a mulch, it makes a nice home for insects who in turn, help with pest control.

Pine Needles

Pine needles are good if you are looking to lower the pH of the soil without causing any problems to plants. They do not become compact and still do a good job at suppressing weeds and retaining moisture in the soil.

Wood Chips

A big advantage of wood chips / bark is they take longer to break down so you don’t have to apply them as often. They are available in different grades – fine, medium and coarse. Go for the medium to coarse grade that don’t absorb moisture and allow water to penetrate the soil. If you use a finer coarse of wood chip, it absorbs moisture and can become a breeding ground for weed seeds. It is best to use wood chip / bark mulches around trees, shrubs and in garden beds where you won’t be doing a lot of digging.


Using compost as a mulch is best to use if you have too much compost. It has a dual purpose as it feeds and insulates the soil. If you are using your own homemade compost to mulch, aim to have large particles of compost. To do this, sieve your compost into two particle sizes: coarse to use as mulch; fine to dig into soil as a fertiliser or soil conditioner.

Apply a thick layer (5-10cm) over the soil, extending out to approximately 31cm from the plants. The mulch will slowly work it’s way through the soil during spring and summer and you will need to add additional layers every month or so.

Dried Leaves

Leaves can be used as mulch anywhere in the garden and you don’t have to go to the shop to buy them. They will also encourage earthworms into your garden soil. Leaves as mulch on the garden can look messy and it is best to apply them in spring before plants spread out and in autumn. You can keep them stored in the Burgon & Ball Leaf Compost Sacks. Leaves can mat together, go over them with a rake to loosen them up.

Plasitic sheets over plants in a field, newspapers and fabric with plants growing through


Black Plastic

Plastic fabric is best applied around shrubs and trees as they don’t need to be fertilised that often. The downside of plastic is that it gets very hot, especially in the summer. It does suppress weed seeds but also kills all the good nutrients in the soil. Plastic is also detrimental to the soil as it decomposes.

To allow water to pass through the plastic, cut holes in the plastic and check for puddles accumulating. You will need to cut more holes in the plastic if water starts to accumulate on top.

Landscape Fabric

Similar to plastic, landscape fabric is best applied around shrubs and trees. Fabric mats are excellent for long-term weed control and moisture conservation. Cut holes in the fabric to allow water to pass through. After a few years, the landscape fabric will decompose and you will start seeing weeds coming through.


Newspaper is becoming more popular to use as mulch, especially as most newspapers have switched over to soy-based black inks and hydrogen peroxide for bleaching pulp. Avoid using colored or glossy inks as mulch to protect your plants.

Newspaper has great moisture retention and acts like other organic mulches suppressing weeds and controlling soil temperatures. Flat sheets of cardboard are great at suppressing weeds around trees (especially citrus). You do have to create holes in the cardboard to let air and water circulate

Spread a layer of four to eight sheets of newspaper around the plants. Moisten the sheets to keep them in place. The newspaper can look messy; cover with 1 to 3 inches of another organic mulch and the weed protection should last throughout the growing season.

How much mulch do I use?

The depth of mulch depends on the type of mulch used. For coarse mulches a layer of between 2 and 6 centimetres is ideal. Although unprocessed straw mulches from the bale can be applied thicker.
Are there plants that don’t like mulch?
Plants such as bearded iris, don’t like mulch as they need to bake.

When is the best time to mulch?

To get started to mulch your garden is mid-spring and mid-autumn. Once the first layer is down, you can top-up at any time. There are a few rules as to when you should not mulch. Avoid mulching too early in spring, it will take the soil longer to warm up and harder for plants to grow through the soil. Also, mulching on a hot summers day will retain the heat in the soil making it too hot for plants to grow.

A simple rule of thumb when mulching is to prepare your soil in a few simple steps:

  1. Remove any weeds
  2. Give the soil a good watering
  3. Apply the mulch
  4. Water over the mulch

Looking after the soil with mulch will save you a lot of time and effort in the long run. Make mulching part of your regular gardening routine and reap the benefits of having a healthy and productive garden.