To Mulch Or Not To Mulch

7 Sep 2020
by Louise Steenkamp

Some gardeners are devout mulchers whereas others are simply not fans at all. I find myself sitting firmly with the camp who believes its virtues outweigh the vices by far. The following is by no means a scientific journal, but rather an introduction aimed at beginners to point out the main factors at play. At the end you need to establish for yourself if you consider mulching a friend or a foe. I will write from my own experience only, and given that you already know in which corner I find myself, I will endeavour to write as unbiased as possible.

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Let’s start with the benefits

To keep things short I will list my top 3:

Weed suppression – Like all other plants, weeds need light to grow. A thick layer of mulch will block out the light and therefore make life really tough for the weeds. Even though it won’t eliminate weed growth completely, it will certainly leave you with a bundle of extra time, which you don’t have to spend crawling around on all fours doing laborious hand weeding. Always a plus in my book.

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Moisture retention – Another bonus of mulching is its ability to retain valuable moisture in the soil itself. It prevents the soil from drying out, and especially in times of water restrictions, I fail to see why any sensible gardener will refuse the extra help in this department.

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Soil improvement – If using natural mulches, the huge added benefit is the inclusion of organic matter to your soil. It will aerate clay soil and provide structure to sandy soil. As it decomposes over time it will also add valuable nutrients.

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Now let’s look at the drawbacks:

Safe haven for the critters – Even I can’t deny that mulch does create a lovely environment for insects. Some of them can indeed harm your plants, but I would say the bulk of them perform a valuable role in assisting with the breakdown process and making nutrients available to plants.

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Creates nitrogen deficiencies – Also true, when certain types of mulches are used. Unweathered wood-based products like sawdust or wood chips will initially tie up the nitrogen, but as it decomposes it will add nutrients again.

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Fire hazard – Also something I have experienced in the past which could have been avoided completely. Having a smoking worker in a field mulched with straw and plastic irrigation pipes to boot in the heat of summer, was not a good combination. And also the kind of mistake which happens only once. Now you know.

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With my top 3 pro’s and con’s highlighted, we can take a look at different types of mulch.

Organic mulches

These are my cup of tea. Anything that decomposes over a period of time, with all the benefits of mulching mentioned above, gets my vote. You can choose from leaves, bark, wood shavings, grass clippings, compost, hay, straw, cardboard, old newspaper, leaf mold, pine needles, sawdust or even peach pips. Of course you can buy mulch from a local garden centre, but I find if you are on the lookout, you will find many materials you can use. 

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Inorganic mulches

These are artificial mulches and not plant based like organic mulches. Examples are plastic, crushed stone, gravel or geo-textiles. These are not my favourite to use simply because they take more than they give. Stones and gravel get very hot in summer, and do not decompose like organic mulch. Plastic and geo-textiles may sound like a more once off plan, but in the long run they also need to be disposed of, and the sight of landfills full of plastic doesn’t sit well with me.

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By now you should have a better understanding of what mulching entails, and if you want to take part in this marvellous adventure. If the answer is yes, I will give you a few pointers on how to proceed.

  1. Mulch is most effective when it is applied to already moist soil. After you have irrigated or after a rain shower. When applied to dry soil, there is a chance that the soil could remain dry during the rest of the season.
  2. Do not mulch too soon after transplanting or sowing. Wait for the plants to be around 5-10cm high before you apply mulch. 
  3. The thickness of your mulch will be determined by the material you use. Generally a finer mulch will be applied thinner, and a coarse mulch can be applied thicker. 
  4. Avoid mulching in very wet swampy areas.
  5. Think twice before using a mulch with a lot of seeds in it. You may end up importing more unwanted weeds. 
  6. After the growing season, I like to work the semi decomposed mulch back into the bed, and add plenty of organic material to the soil in the process of doing so.
  7. Do not mulch too close to the stems of plants. I leave a 2-3cm space around annuals open. With perennials it’s fine to mulch closer.

And there you have it – HAPPY MULCHING! OR NOT…

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