Mulch vs. Compost – Which Should You Use?

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Compost and mulch – what are they? And what’s the difference? In this article, we are going to take a close look at both mulch and compost and explain which you need and when you should use them. 

We don’t want to waste your time, so here’s the bottom line: you should be using both of these strategies. Read on to find out more… 

What is Mulch?

Gardener adding mulch to flower bed

Mulch is a catch-all name for any one of several substances that are placed over the soil to cover it. It can be made from many different materials, including organic scraps, grass clippings, kitchen scraps, hay, straw, grass, leaves, shredded newspapers, wool, cardboard, sawdust, and shells.

The Two Types of Mulch

There are two types of mulch: Inorganic and Organic. Organic mulch is mulch made from organic matter, which will break down over time (lawn clippings, leaves, etc.).  Inorganic mulch, such as shells, stones, black plastic, fabrics or rocks, do not break down and decompose. 

Both types of mulch will carry out the function of suppressing weeds. Organic mulch may also enrich the soil as they decompose. Inorganic mulch, such as black plastic, can be more efficient at warming the soil at nighttime, which is great for plants that like warm conditions. Inorganic mulches may initially cost more, but because they either do not decompose or decompose over a long period, they can be more cost-efficient because they do not need to be renewed so often.

Mulch Benefits 

Garden mulch provides many benefits:

  • It keeps the soil moist by helping retain moisture
  • It suppresses weed growth
  • It prevents the soil from overheating
  • It reduces erosion (which causes nutrient loss)
  • It improves the fertility of the soil as it decomposes (organic only)
  • It can have a decorative effect for your garden

For obvious reasons, inorganic material does not provide this last benefit!

Quick warning: You can use many things as mulch but steer clear of using pet waste as it can carry parasites that can spread to humans. You should also avoid long twigs and thick roots (very slow to decompose), as well as foods such as meat, bones, fish skins, milk, or butter.

How to Use Mulch

Start by weeding the area around the plants before you mulch. Once the area is free of weeds, lay down the mulch. You should make it thick enough to ensure that no fresh weeds can grow through it. 

To achieve a total barrier against weeds, you may need between two and four inches of mulch. In shady spots in your garden, you’ll need thinner mulch. Sunny spots will require thicker mulch. Some materials, like hay, will need more than four inches as they’ll quickly compress down. If you are using plastic sheeting or something similar, a single layer will normally suffice.

If the area is a problem area for weeds, then you might want to consider “double mulching.” This involves weeding the area, watering it and then laying down sheets of newspaper. Finally lay mulch on top of the newspaper. This provides your garden with near-perfect protection from weeds.

Some organic materials retain water, which can slow the warming of soil. An example would be wood chips. You may want to rake some away from perennials to speed up growth. You should also be aware that wet mulch left piled against stems can cause rot.

What is Compost?

Compost is decomposed organic matter that acts as a fertilizer. Most gardeners maintain their own compost pile into which they put a mixture of green matter (for example, lawn clippings and kitchen scraps) and brown/dry matter (for example, dried grass and fall leaves). 

Composting requires having a good mix of green and brown. Greens are rich in nitrogen or protein. These items will add to heat the compost because they assist the microorganisms in the compost to grow and multiply faster. The browns are carbon or carbohydrate-rich materials. The job of the browns is to act as a food source to the microorganisms in the compost.

You add organic materials to the top and remove the compost from the bottom. The optimum mix of materials is about two parts of brown/dry materials to every one part of the green. Of course, if you want to delve into the science, compost creation can get more complex than that (it’s all to do with the ratio of carbon and nitrogen) – but we find this simple compost ratio works pretty well as a guideline.

Compost Benefits

Compost provides many advantages for your garden:

  • Naturally enriches the soil with vital nutrients
  • Is a natural way to reuse organic waste
  • Reduces reliance on chemicals to improve soil
  • Keeps your plants growing and healthy and helps prevent disease

How to Use Compost

Typically you want to work compost into the soil. Try working a couple of inches of compost into about six inches of soil – you don’t want the plant to only have compost near it. You can add compost to your garden at any time of year, and some plants, such as tomatoes and corn, will benefit from a little extra compost regularly.

Compost can also be used as a mulch, but you need a large volume, so it often isn’t practical. If you do this it is better to sprinkle a fine layer of compost on the surface and then add another mulch on top of that.

Mulch vs. Compost: What’s The Verdict?

As we’ve seen, mulch and compost perform two different roles. Mulch is used to reduce weeds, improve the soil (if organic), stop erosion, and keep the soil moist. Compost is used to improve the soil and provide vital nutrients to your plants. This is normally achieved by digging it in so that the good stuff is close to the roots of your plants.

Compost and mulch are both beneficial for your garden and plants; you don’t have to choose one or the other!

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