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What is Mulch and How to Use It in Your Garden

Mulch is any material that we place over the soil on our garden beds. There are a number of different organic and inorganic mulches, each with its own pros and cons.

Adding mulch to your garden beds is one of the best things you can do to slow down moisture evaporation from the soil, suppress weed growth, and keep your plants happy and thriving.

What is mulch?

Mulch is any material that we place over the soil on our garden beds.

There are inorganic mulches such as crushed rock, living mulches such as groundcover plants, and organic mulches such as wood chips, straw, or sugarcane mulch.

What does mulch do?

bricks and mulch | Plant care

In essence, mulch has a number of primary purposes.

Firstly, because it covers the soil completely, it reduces the amount of water that evaporates from the soil. This is particularly useful during periods of hot dry weather as the soil will stay moist for longer.

Mulch is also a good soil temperature regulator. It will keep the soil warmer during cold weather and cooler during the hotter months.

Mulch also suppresses the growth of weeds. In all soil, there are weed seeds that are just waiting for the right conditions to germinate and grow.

By placing a layer of mulch over the soil, the weed seeds that are buried beneath the mulch will not have enough energy to break through the surface or they won’t get enough light to germinate in the first place. 

In addition, any weeds that are able to break through the layer of mulch are usually very easy to pull out.

Using organic mulches on your garden beds will also benefit the soil. As these products break down, they add valuable nutrients to the soil. They also help to improve the structure of the soil, making clay soils more workable and sandy soils more water-retentive.

And a final advantage of using mulch is that it will protect the soil from eroding and getting washed away during periods of heavy rain.

Different types of mulch

Mulch | Plant care

There are many different types of mulches that you can use in your garden.

Here are the more common ones:

Straw, hay and lucerne

Straw, hay, or lucerne is perfect for vegetable gardens as it decomposes quickly and adds plenty of nitrogen to the soil.

Pros

  • Breaks down quickly
  • Adds nutrients to the soil
  • Covers the soil to prevent moisture loss

Cons

  • Needs to be topped up regularly

Sugarcane mulch

This is made from dried sugar cane leaves and is a by-product of the sugar cane growing industry.

Pros

  • Covers the soil to prevent moisture loss
  • Adds nutrients to the soil as it breaks down

Cons

  • Needs to be replaced regularly

Pine Bark

Pine bark looks great and will last for a longer period of time.

Pros

  • Looks great on your garden beds
  • Helps soil to retain moisture and controls the temperature
  • Will add nutrients to the soil as it breaks down
  • Improves the structure of the soil

Cons

  • Will need replacing around once a year or so

Wood Chips

You can easily get wood chips from local tree pruners that may be in your area. This is one of the most inexpensive mulches and works really well.

Pros

  • Looks good in the garden and is fairly inexpensive
  • Great for suppressing weeds
  • Helps soil to retain moisture
  • Will improve soil structure and add nutrients when it eventually breaks down

Cons

  • You might have to wait for local tree pruners to be in your area to receive a load
  • It will break down eventually and will need to be replaced

Gravel and pebbles

Gravel and different types of pebbles can be used as a covering for your soil to help retain moisture and suppress weed growth. These are particularly useful in hot, dry areas.

Pros

  • Creates a permanent soil covering
  • Reduces moisture loss and helps to regulate the soil temperature
  • Doesn’t need to be replaced

Cons

  • Does not break down and add nutrients to the soil

Black plastic, weed mat and landscape fabric

Weed mats are mainly designed to suppress weed growth. They will help to regulate the soil temperature and prevent too much moisture loss.

However, these products can break down over time and many don’t allow water to penetrate deep into the soil.

Pros

  • Fairly good at suppressing weeds
  • Helps to regulate the soil temperature

Cons

  • Not very attractive
  • Will not allow water to penetrate deep into the soil
  • Does not add nutrients to the soil

Organic vs inorganic mulch

The main difference between organic and inorganic mulches is that organic mulches will break down over time and help to add nutrients to the soil while inorganic mulches will not.

However, organic mulches will need to be replaced while inorganic mulches are a more permanent solution.

The best mulch for vegetable gardens

vegetable garden 2 | Plant care

The only type of mulch that I regularly use on my vegetable gardens is pea straw or sugar cane mulch. These materials are great for covering the soil and naturally suppressing weeds.

However, the major benefit I find is that these types of mulches will break down fairly quickly and add valuable nutrients to the soil.

They also help to improve the soil structure and encourage microbial activity in the soil.

In essence, this creates healthy soil for vegetables to grow and thrive in.

How to mulch a garden

Mulching your garden is fairly easy although it can take a bit of time and effort.

After you’ve decided on the type of mulch that you want to use, it’s just a case of spreading it over your garden beds to a thickness of around 50 to 100 mm.

It is traditionally recommended to layer mulch to a thickness of 100mm. However, Angus Stewart from Gardening Australia has trialled laying mulch only 50mm thick and has had good results.

FAQ

What is the best time to mulch in Australia?

In Australia, you can mulch your garden beds at any time of the year. Primarily, you want to do it before the heat of summer if you want to suppress weeds, keep the soil cooler and limit moisture loss from the soil.

Will plants grow through mulch?

Plants will grow happily in a mulched garden bed as long as you plant them in the soil beneath the mulch.

Should you use grass clippings as mulch?

You can use grass clippings as mulch but these may also contain weeds seeds and will break down fairly quickly. It’s also best to age your clippings for a few weeks first.

What is the cheapest mulch?

The cheapest mulch you can use is shredded leaves and grass clippings. However, this will break down fairly quickly. A better alternative is to get some wood chips from a local tree pruner.

Photo of author

Annette Hird

Annette Hird is a gardening expert with many years of experience in a range of gardening related positions. She has an Associate Diploma of Applied Science in Horticulture and has worked in a variety of production nurseries, primarily as a propagator. She has also been responsible for a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.

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