Straw mulch around a plant in the garden

Many gardeners believe that mulch is reserved for flower beds surrounding the home to increase curb appeal or for someone using the Back to Eden gardening method. In reality, mulch can be an incredible asset to any garden. Let’s talk about what mulch is and the benefits of mulch in the garden. 

Uses and Benefits of Mulch in the Garden

What is Mulch?

Mulch is simply a layer of material that is added to the top of the soil. Mulch comes in many different forms and offers a plethora of benefits to vegetable or flower gardens.

Common Types of Mulch

There are many different types of mulch, but they can be broken down into two basic categories: organic and inorganic.

Organic Mulches

Organic mulch is made up of living or previously living organic material. This type of mulch naturally breaks down to improve the quality of the soil.

The most popular mulches are wood mulches like pine bark mulch, hardwood mulch, wood chips, and cedar mulch. 

Other organic mulches include:

  • Pine Straw- dried out pine needles
  • Grass clippings
  • Leaf Litter
  • Hay or Straw
Organic mulch being shoveled out of a truck bed

Inorganic Mulches

Inorganic mulches are made up of non-living materials that do not decompose like the living matter in organic mulch. 

They do not enrich the soil, but they do serve other purposes in the garden. 

The most common inorganic mulches include:

  • Landscape Fabric
  • Black Plastic Sheeting
  • Rubber mulch
  • Rocks/Stones/Gravel
Inorganic mulch: black plastic sheeting being used around tomato plants

8 Benefits of Mulch in the Garden

There are many great benefits to using mulch in a vegetable garden or flower beds.

 1. Regulates Soil Temperature

Mulch helps to keep the soil cool during the summer heat. When a garden is mulched, the surface of soil is covered… This acts as a natural shade and insulation which helps to regulate soil temperature. 

2. Retains Soil Moisture

Mulch on top of a garden reduces soil evaporation. This means that water stays in the soil to hydrate plant roots much longer than it would in bare soil. This is especially important for sandy soils as they tend to dry out quickly.

A garden that is properly mulched will reduce the amount that you need to water the soil. That’s great for the plants and for you!

3. Slows Soil Erosion

Garden mulch also serves as a protective layer from the elements. The mulch helps to hold the soil in place during high wind, heavy rain, and hail. 

Mulch added on top of clay soil will slow the water run-off by giving the clay more time to absorb the water and it will hold sandy soil in place.

4. Reduces Weed Growth

If you don’t like pulling weeds, add a good mulch to your garden. Mulch is a great weed control method. It acts as a natural barrier that will block sunlight and smother weed seeds as they try to germinate. You may still have some weed growth, but much less than a garden with bare soil.

Leaf Litter mulch in the garden

5. Improves Soil Structure

Decomposing mulch will help to decrease soil compaction in clay soils which will encourage root growth.

Mulch works to bind sandy soils by holding water in and reducing soil erosion as mentioned previously. 

6. Improve Soil Health

Organic mulch will increase soil health over time. The mulch will break down into the soil enriching it with organic matter. As it breaks down, it will attract insects, worms, and beneficial microbes that will improve the soil even more.

7. Increases Growing Season

Just as mulch can keep the soil cool in the summer, it can also trap heat during winter. By covering the soil surface, mulch serves as an insulator that can warm the soil and allow you to grow into the colder months. 

8. Prevents Plant Diseases

Adding a good mulch layer on top of bare soil will reduce the amount of soil and water that splashes on the leaves. This helps to prevent the spread of fungal and bacterial diseases.

Straw mulch in the garden around strawberries

Mulching Considerations

Get the Most Out of Your Mulch

Kill weeds before mulching. You can do this by covering the garden area with a tarp to suffocate the weeds or you can pull them by hand. 

You should also water the soil thoroughly before adding mulch. This will jumpstart the moisture retention properties of the mulch. 

Choose the Right Mulch

Think about what your goals are and choose a mulch that will help you to achieve those goals.

  • If you want to improve your soil, choose an organic mulch. 
  • If you want a garden that requires little maintenance but doesn’t improve the soil over time, choose an inorganic mulch. You will need to keep inorganic mulch free of soil or compostable materials or seeds will germinate in it and grow weeds through the fabric.
  • If using wood mulch, be sure that it isn’t fresh wood. Wood mulch that is too fresh can potentially increase the acidity of your soil and tie up some of the nitrogen. Wood mulch isn’t recommended for gardens that will be growing plants with high nitrogen needs, such as tomatoes, peppers, squash, corn, etc. The wood mulch will tie up the available nitrogen for the plants while they go through a slow composting process. Do not use bark mulch or mulch made from large branches as they take much longer to break down and tie up nitrogen longer.
  • Exercise caution when sourcing organic mulches. Leaves gathered from suburban lawns often have been in contact with herbicides sprayed on the lawn over the summer. Straw is an excellent choice if you don’t want to risk bringing weed seeds into your garden, however, most grains are heavily sprayed. Choose an organic straw source. Organic or no-spray hay can also work well. Some may be concerned about weed seeds but generally, you can cover young tender seedlings with another heavy layer of mulch and kill them. Source hay mulch that was stored in a field for at least a year. Most weed seeds will have been heated (and killed) or already germinated. An increasing concern with hay mulch stems from a newer herbicide, Grazon, that does not break down. (This also causes an issue with compost made from manure of animals fed hay sprayed with aminopyralid-based herbicides.) It is best to ask the farmer who grew the hay what his growing practices are and what chemicals he uses in his field. Learn more about aminopyralid herbicides, such as Grazon, here.

Mulch Depth

If you are using coarse mulch, you can add 4-6 inches to the soil surface. 

When adding fine mulches to your garden, add 2-3 inches to the top of the soil. Water and sunlight cannot travel through fine mulch as easily as it can travel through a coarse material.  If you add too much, the plants can suffocate and dehydrate.

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