Using mulch to retain moisture and fight weeds

Mulch with leaf mold
Mulch with leaf mold

Mulch  refers to dead organic material, such as leaves, bark or even grass clippings. It is typically used to help plants grow. You can make your own mulch, or you can buy it in nurseries and hardware stores.

Mulch has many uses. It can, for instance, be used to:

  • Retain soil moisture. For this purpose, you can mix it in with your soil, you can spread it over the soil, or both.
  • Lighten up your soil. What makes your soil rich and alive are the good microorganisms that live in it. These need two main things to thrive, namely water and air. If your soil is too heavy or clayey, mixing in some mulch may help tremendously.
  • Fight weeds. Add a layer of mulch over the soil in your flower bed and it may prevent weed seeds blown in by the wind from taking root.

As you will see below, different mulches can be used for different purposes.

Retaining soil moisture

There are a number of plants that can survive through droughts or drought like conditions, but most plants cannot survive for long when deprived of water for extended periods of time.

If you are living in a location that typically enjoys normal conditions, as opposed to extreme conditions, you typically grow plants that are not well adapted to extreme conditions. With climate change, on the other hand, weather patterns can change enough to threaten the very survival of many plants.

Plants that grow in soil that is poor in organic matter and that tends to drain very well are most at risk of not making it through a dry spell. Combine this with the sun’s harsh rays shinning directly on the soil, and you have a recipe for disaster.

To give your plants a fighting chance against such extremes, you can use mulch two ways:

  • Mixing mulch with your soil will make it richer and thus help retain moisture. The best mulch types for this are typically peat moss, leaf mold and grass clippings. Note that you can make your own mulch with a mulching machine and that you can use your mulch to make your own compost. Composted mulch retains moisture and provides lots of natural nutrients. Mixing in some manure will boost both your plants and the micro organisms present in the soil.
  • Adding mulch on the ground will block the sun’s rays and trap the humidity in the soil. Newly planted trees and shrubs may get a much better chance of survival if you add a good layer of mulch over the soil around the trunk. The best mulches for this purpose are typically bark chips or wood chips.

About peat moss

It is not uncommon for people to add peat moss to the soil when adding new plants to their yard or flower bed. Peat moss certainly is a good choice, if you want the soil to retain moisture, but there are a couple of things you should know about peat moss.

  • Peat moss comes from peat bogs. Peat bogs were long considered to be nothing more than wastelands. We now know that they are important ecosystems that take a very long time to develop.  A number of conservationists warn that peat bogs, like wetlands, should preserved and not open to commercial exploitation.
  • Peat moss acidifies soils. Soil PH is a very important factor in plant health. Although adding a lot of peat moss to your soil may make your acidic soil loving plants happy, it will make your alkaline soil loving plants suffer. So your rhododendrons may be quite happy, but your acacias may starve.

Lightening up heavy soils

Heavy soils are typically rich in clay. Few plants can grow in such soils, as they are often rich in nutrients, but poor in organic matter and air. The best way to deal with heavy soils is to add the right mulch and to grow the right plants. To lighten up such soils, tree bark is your best choice. For detailed information on this and on which plants to choose, see our page on clay soil plants.

Fighting weeds with mulch

Many of the weeds on your yard may be a gift from your neighbours. Seeds blown in by the wind lend on your lawn and around your plants, they take root and multiply.

The best way to prevent these seeds from taking root on your lawn, is to keep your turf long. And the best way to do the same for the soil around your plants is to use mulch. The best mulches for this purpose are typically bark chips or wood chips. Shells, such as cocoa shells, are also a good choice, although they are usually more expensive.

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The right plants in the right locations with the right conditions