How to Choose the Organic Mulch for Your Raised Garden Bed?

Organic mulch plays an important role in the planting on raised garden beds and other plant beds. Some plant roots are not heat tolerant or cold tolerant, and mulch can provide a comfortable temperature for plant roots. And some plant roots need to be kept cool while branches and leaves need plenty of light, so adding mulch is especially important at this time. 

Mulch Advantages

1.Reduce evaporation of water

The use of mulch can bring many benefits. In summer, mulch can keep the soil moist, reduce water evaporation, so gardeners do not need to water frequently. With mulch, the soil will not be dry and hard after baking for a whole day in the sun.

2.Moisture retention

Mulch has a moisturizing effect. In some places with high temperatures and strong light, the soil moisture is quickly dissipated after watering. In these dry and hot places, it is better to use mulch to retain moisture. However, if the garden is hot and humid, mulch is not necessary because it can lead to the growth of mold.

3.Root protection

Wood bark, sawdust, and fallen leaves are common mulches in our lives. Over time, this mulch slowly decomposes into more humus-rich, decomposing soil. These decomposing materials contain nutrients that benefit the plant's root system.

4.Weed reduction

Mulch can also prevent weeds. If mulch is added to a raised garden bed, light does not reach the soil and weed germination is inhibited. This prevents weeds from absorbing nutrients from the plants, which is a great help to the growth of garden bed plants.

5.Keeping warm

A thick layer of mulch can be placed on the surface of the soil before the winter frost comes, which helps to avoid frostbite on the roots of the plants. The thickness of mulch on a raised garden bed is usually around 1 inch. If mulch is used in winter to protect the bottom of the root stock from frostbite, it needs to be more than 2 inches to be effective. If the mulch is spread too thickly, it will cause the roots to suffocate.

6.Improving soil nutrients

Moreover, organic mulch will be slowly decomposed over time, so the structure and fertility of the soil will increase. So adding mulch helps improve the soil quality and reduce the use of chemical fertilizers.

Organic Mulch for Your Raised Garden Bed

Types of Mulch

1.Wood bark

Wood bark is a common and environmentally friendly type of mulch material, and its sources are also wide. Wood bark is one of the more effective mulches in the garden planting process and decomposes relatively slowly. Pine and fir bark decompose more easily than ordinary shredded bark. To use bark as mulch, it needs to be processed into finer wood chips for better decomposition.


Fresh grass

Fresh grass is freely available from the garden, and it decomposes quickly and can be turned into soil nutrients. If using fresh grass as mulch, you can lay a thin layer on the raised garden bed first, and then lay another layer after it has dried to avoid the fresh grass rotting. And do not use Bermuda grass.

When using grass as mulch, you should pay attention to the following points:

  • Avoid pulling grass in wet weather and do not leave it in the planting area to prevent it from regrowing.
  • Remove the long roots from the planting area and dry them in the sun. After it's dried, burn them to make grass ashes (Grass ashes is a rare organic nutrient contain. Because it almost contains all the mineral elements that plants contain).
  • Pull the grass a day or two after the rain, when the soil is looser and it is easier to pull and dry.


Like other natural mulches, hay can add nutrients to the soil when it decomposes. However, it is important to note that when using hay for mulching, avoid using seeded hay as much as possible to avoid seeds germinating and becoming weeds.

Organic Mulch for Your Raised Garden Bed


Straw is a clean and hygienic organic mulch as it prevents soil from touching the fruit. Especially in summer, placing a layer of straw mulch in the garden bed can have a particularly good cooling and sun protection effect. Among the grass mulch options, straw is the preferred mulch. For one thing, there is no risk of weeding, and it has all the advantages of natural mulch.

4. Fallen leaves

Fallen leaves, an extra gift from nature, are also a good choice of mulch for raised garden beds. Before using fallen leaves for mulching, it is recommended to chop them finely and shred them. This will not only decompose faster but also avoid clumps during the decomposition of the leaves.

5. Compost

Compost looks like soil, but the color of compost mulch is a little darker than soil. Compost can decompose quickly and can both fertilize and moisturize the soil. If you are buying compost, the price is relatively cheap. Of course, compost is easy to make, and you can consider making it by yourself.

In the raised garden bed, you can place the compost in the middle layer, so that the plant roots fully absorb nutrients, but it can also be placed at the top to create a certain moisture effect. There are also many gardeners who will be placed directly on the ground for compost planting.

6.Pine needles

Pine needles are natural mulch and can be collected continuously under pine trees. Laying some pine needles around the plants on the ground, or at the top of the garden bed, will also keep soil moisture and pests away, such as common snails.


Sawdust is also suitable as mulch and can be used in garden beds or on the ground. If you use sawdust as mulch, it is best to choose sawdust made from natural wood. The sawdust itself is acidic and can be used on soil that likes acidic soil, such as blueberries. It can be placed around shrubs and trees. However, if you use sawdust, the soil will easily lack nitrogen fertilizer, so the amount of sawdust used should not be too much, and you can mix some other mulch to improve this situation.

8. Inorganic mulch: Pea gravel and rocks

Pea gravel and rocks are inorganic materials, so they do not decompose in the garden, which also means they do not improve the soil over time, but they are effective in preventing weed growth. Covered rocks can get hot, so stones are frequently used to cover garden plants on the ground that like to dry out, such as ornamental grass plants.

Organic Mulch for raised beds

The use of mulch

How to add mulch:

The best woody species for hügelbeds are alder, apple, cottonwood, maple, oak, poplar, dry willow, and birch.If you are planting seeds, add a 2-3 inch layer of mulch on top. It is best to wait for the seeds to germinate and grow a few inches tall before placing mulch. If mulch is placed as soon as the seeds are planted, it will block the sunlight needed for germination, making it difficult for the seeds to germinate.

It is also important to place mulch around the crop and not cover the seedlings. Leave an inch of space for the root stock of the plant. If you are using straw, wood chips, or leaves as mulch, they may absorb some of the nutrients from the soil. So it’s feasible to add some organic fertilizer to the soil before adding mulch.


The mulch on the soil needs to be maintained every year. You can use gardening tools to loosen it and keep it fresh for a longer period of time. Note: If you use garden grids or watering grids on raised garden beds, you need to increase the watering time in the daily watering. because grids will affect the time of water penetration.


Mulch will gradually decompose on the soil surface, so you need to add new mulch every year so that it can work better. The best times to replace mulch are in the spring after planting and also in the fall.