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What Are The Disadvantages of Mulching?

When you want to keep your flower beds tidy it’s understandable that mulching might seem like a good idea. However, mulching may not always be your best option.

The main disadvantages of mulching is that it can create a hiding place for harmful insects, and when applied too thickly can suffocate your plants by overheating the soil and starving them of light and water.

So in this article we’ll look at when it can be a disadvantage to mulch – despite it being recommended as a magic solution by many gardening sites.

What Is Mulching?

Mulch is basically any material that’s put on top of the soil in your growing beds to suppress weeds. There are two types of mulch – organic and synthetic.

When used properly, mulching also has the effect of moisturising the soil and keeping it cool, whilst also introducing nutrients in the case of rotting organic mulches.

A good mulch can stop frost damaging plants, and can also help to regulate drainage in your flower beds and vegetable patches.

Mulching also helps your beds to look great too – so they appear neat, tidy and well kept. This is as important to many people as the pros and cons mulches have for plants.

However, not all plants respond well to mulching, especially perennials that prefer a rocky style of soil such as lavender or lamb’s ears. Plants such as these can be completely suffocated by organic leaf or wood chip mulches, as they interfere with the process of photosynthesis.

So it pays to do some research into the types of plants you’re going to be mulching around – to se if they respond well to it.

Types of Mulching

As mentioned, there are two main types of mulches – organic and synthetic. While both have some advantages if not applied too thickly, they also have some disadvantages too. Here are the two types broken down:

Organic Mulches

If used at the correct depth for the types of plants you have, organic mulches are really the only option if you want to protect your plants. Here are some of the best:

  • Bark – pretty much the industry standard – it can be shredded, chipped, or chunked. Pine, cedar and cypress are all common, and are produced in massive quantities as by-products of forestry and paper manufacture.
  • Leaves – naturally occurring and abundant in the fall, they can add phosphorus, carbon and potassium into the soil. Can suffocate plants if used incorrectly. 
  • Grass cuttings – another freely available mulch, but is often applied far to thickly to provide any benefits. Only 2-4 inches maximum should be used.
  • Pine needles – create a fine carpet of needles over the soil, but can introduce too much acidity into the earth as they decompose.
  • Organic wood chips – chips of wood and sawdust that haven’t been treated can be a good mulch. However, you can only really tell if they’ve had any kind of wood treatment if they start to smell sour when rotting. This means they’ll release high levels of acidity into the soil and could kill plants.
  • Straw – abundant and relatively inexpensive, straw is a decent mulch but it can become black and messy looking as it decomposes. 
  • Newspaper – put through the shredder this can be a free and easy mulching solution. However, do you really want all that harmful ink seeping into your plant roots as it rots? 
  • Cocoa shells – these look and smell nice, and will introduce potash, nitrogen and phosphates into the soil. Can be an expensive option though.

Synthetic Mulches

Mulches that use synthetic materials are really quite brutal for the soil, as they completely suffocate growth. This is great for weeds, but not so good if you accidentally suppress the development of your flowers or vegetables. Some of these synthetic options include:

  • Gravel & stone chips – a decent option for mediterranean style gardens with the plants to match, but can be a nightmare to remove from the soil afterwards. As the sun bakes down on gravel it can cause the soil underneath to overheat too.
  • Dyed wood mulch – growing in popularity, these wood chip mulches are artificially dyed in attractive colors to make your garden look more appealing. However, the chemicals used to make these dyes can seep down into the soil and harm your plant roots. So there are expensive and not a good idea.
  • Black plastic – frequently used around trees, plastic sheeting does completely suppress weeds, but it does also make the soil extremely hot and dry – and can end up killing plant roots and important soil microbes. Even if you cut holes in it, black plastic can totally starve the soil of moisture. 
  • Newspaper – put through the shredder this can be a free and easy mulching solution. However, do you really want all that harmful ink seeping into your plant roots as it rots? 
  • Landscaping fabric – while more porous than black plastic, landscaping fabric can still dry out and overheat the soil – so you could end up accidentally killing all plant roots underneath (not just the weeds). An expensive option too.
types of mulching
Are Wood Chips Good for Mulching?

10 Disadvantages of Mulching

While there are undoubtedly some advantages to using mulches in the right circumstances, inexperienced gardeners can end up misusing them and end up harming the plants they are trying to protect.

So here are some things to look out for when considering using mulches in your flower beds and vegetable patches…

  • Over-mulching – adding your chosen mulch too thickly to your growing beds can first bury and then suffocate your plants. Stick to a 2-4 inch layer to b safe. If your mulching material if fine then only use it sparingly.
  • Encouraging pests – slugs and snails are amazing creatures, but not so much when they’re eating your plants. Using organic mulches can introduce these harmful pests (and others) to you soil, and they could end up infesting your flower beds. If you do use bark, leaves or similar, you may have to use slug pellets to deter the harmful bugs.
  • Drying out the soil – organic mulches used too thickly – and all synthetic mulches – can completely dry out the soil underneath. This is good for killing weeds, but not so great for encouraging water flow through to your plant roots.
  • Overheating the soil – again, some natural mulching solutions and all the artificial ones can overheat the soil below if piled up too thickly. Aim for that 2-4 inches to avoid your mulch having the opposite effect than you intended.
  • Nitrogen leeching – sawdust and wood chips can leech beneficial nitrogen from the soil as they rot down. So if this is your mulch of choice you may need to use nitrogen-rich fertiliser to compensate. Soybean meal is a good option here.
  • Air starvation – applying either an artificial or eco-friendly mulch too copiously can starve the soil of oxygen, which will be detrimental to plant root growth.
  • Sunlight starvation – because all mulches block sunlight from entering the soil, this can be harmful when it comes to the germination process. So don’t ever use mulches on seed beds.
  • Rain water pooling – when it rains heavily on your organic mulch, it can turn a tidy, well maintained garden into mess of pooling water and rotting organic matter. The solution again is not to apply your mulch too thickly, so it can drain properly.
  • Acidity problems – artificial mulches such as dyed/treated wood chips, and newspaper, and organic options like pine needles – can all add harmful levels of acidity into the soil that can stunt plant growth.
  • Stopping hoeing – it’s best practise to space plants out enough so you can hoe in-between. Hoeing is beneficial in that it breaks up the soil, aiding water flow to plant roots and aerating the earth. It also means weeds can be controlled manually. Using a thick carpet of mulch often results in plants being put too close together, so you can never hoe the ground.
disadvantages of mulching
What Are the Disadvantages of Mulching Grass and Bark?


If used properly for the types of plants you have in your garden, and also at a safe depth of between 2-4 inches – mulching can offer many benefits for your plants.

However, with many organic and artificial mulches starving your soil of light, water and air – together with adding too much heat, harmful pests and high levels of acidity, then it often seems like the disadvantages of mulching can outweigh the positives.

Ultimately, your choice of which mulching solution to use – or indeed whether you end up using mulch at all – is all down to the exact conditions in your garden, the range of plants you grow, and your experience as a gardener.

However, for homeowners who just want to entertain in the garden and enjoy a great looking outside space, it does not seem that mulching is the magic, catch-all solution that many people want it to be.

To finish, this video on the pros and cons of mulching is excellent…

Mark H.

Homeowner and property investor Mark H. aspires to bring you the very best outdoor living content, based on his years of experience managing outside spaces. Read more >