Last Modified: February 13, 2024


What Is It And What Is It Made Of?

Ornamental bark mulch close up

By Ben Parrot - Landscape Gardener & Amateur Geologist


Mulching is one of the best kept secrets and gardening – a simple yet powerful technique that can make a world of difference to the success of your garden. But with so many types available, how do you know which one is right for your project or planter?

In this article, we’ll cover most of the different types of mulch, their benefits, and how much mulch is best practice for different applications. So let's get started on this de-composition of everything that is mulch.

Key Takeaways

  • Benefits: Weed suppression, moisture retention, and improved soil health are just a few.
  • Organic Mulches: Best for overall garden performance.
  • Inorganic Mulches: Are lower maintenance and more durable but have their downsides.
  • Applying Mulch: There are benefits in learning the best techniques for applying mulch.
  • Materials: What to use as mulch, here are eight types.
  • Membranes: Plastic and landscaping fabric should be used with caution.
Landscaping bark around shrubs in a garden border. Jpg

What Is Mulch?

Garden mulch is a critical element in most garden applications. It is any material spread over soil to improve it in some way, either in a practical or decorative sense. There are organic and inorganic types of mulch, and regardless of the type, it is used to conserve soil moisture, control weeds, regulate soil temperature, prevent soil erosion, and beautify garden beds.

Benefits Of Mulching Garden Soils

One advantage of using garden mulch is the way it can improve the look of your gardens, borders and planters. If you prefer the natural look with its rich, dark tones of leaf mould, or the environmentally-friendly, versatility of permanent leaf mulch, there is something out there to suit every true gardeners taste.

Dead dried leaves for mulching. Jpg

However, perhaps you're more interested in the role mulch plays in improving soil health and promoting plant growths. Gardens greatly benefit from mulching for many reasons. Here are some key benefits:

  • Acts as a weed suppressant, by blocking sunlight and preventing germination, reducing maintenance.
  • Offers a protective barrier for garden soil, helping to retain soil moisture and regulate its temperature.
  • Promotes plant growth by providing a nutrient-rich environment.
  • Reduces water consumption by minimising evaporation.
  • Prevent frost damage by stopping the freezing of soil below the surface.

By mulching, you can enjoy the benefits of a healthy and thriving garden by creating an optimal environment for your plants, trees and shrubs to grow. Next we cover the two main categories of mulch; organic and inorganic.

Turning garden compost. Jpg

What Is Mulch Made Of?

You might ask: what is mulch made of? Well, there are two main types of mulch: organic and inorganic. Organic mulch is derived from natural materials, such as wood chips, shredded leaves, and grass clippings, while inorganic mulch is made from synthetic or non-organic materials like plastic, landscape fabric, and different types of gravel. Also, choosing mulches with peat moss are a less sustainable option.

Both types of mulch have their pros and cons, and the choice largely depends on your gardening goals and preferences. The next few sections will go into a more detailed look at organic and inorganic mulches, including their characteristics, benefits, and best practices.

Organic Mulch

Biodegradable mulches are the go-to choice for many gardeners due to the numerous benefits. Organic mulches include materials such as:

  • Wood chip
  • Shredded bark or leaves
  • Grass clippings
  • Compost
  • Straw or hay

For example, when it comes to your vegetable crops or an allotment, the deployment of a thick layer of straw or hay can be an ideal choice. Not only does it suppress weeds, but it will reduce the amount of water your plants need and add organic matter to the soil as it slowly breaks down. It's also very economical!

Straw mulch for growing fruit and vegetables. Jpg

Because organic mulches break down over time, they add valuable nutrients and trace elements to the soil, while improving its structure, drainage, and nutrient-holding capacity. This, in turn, also promotes the growth of beneficial microorganisms and helps to regulate soil temperatures by insulating the soil surface, which can be particularly beneficial in colder climates.

Inorganic Mulches

For people seeking a 'permanent mulch', there are also many inorganic types, including natural kinds such as gravel or stone. There are also synthetic mulches like rubber chippings, plastic sheeting or landscape fabric.

Rubber mulch is occasionally used for aesthetic purposes and weed control, although it does have its fair share of controversy over marketing claims that it is more beneficial than an organic mulch. The other two kinds are more commonly used for controlling weed growth in areas that are not generally tended to, so a more permanent solution is desired. They are generally not advisable in your garden to use as a permanent solution, especially if you intend to grow vegetables in the area, subsequently.

In contrast to organic mulch, inorganic mulches are made from synthetic or inorganic materials. Examples include:

  • Recycled tyre rubber
  • Plastic sheets
  • Landscape fabric
  • Gravel and chippings

There are some advantages to using inorganic mulches, such as their durability and low maintenance qualities. They typically require less frequent top ups, making it a more convenient option for some gardeners, particularly in commercial installations. They can be less prone to attracting pests, although there are some types of insects, like some cockroaches, who are more than happy in rubber mulch for instance.

Old car tyre for recycling

Synthetic Mulch

On the other hand, as we have opined in this article, inorganic mulch can come with a raft of downsides. It does not contribute to social health – in fact it can even create a barrier between the soil and air, slowing the exchange of nutrients and water. This can be problematic for plants requiring well-aerated soil to thrive. Plastic mulch, especially laid in sheets, can create humid environments in the soil that is conducive to soil-borne disease growth.

Furthermore, although most of these synthetic and man-made mulches are advertised as non-biodegradable, that does not mean that they don't degrade over time. In fact, there are many reasons to be quite concerned about the leachate rubber produces as it decomposes over time. For one thing, it is known to be quite toxic to aquatic life in the right dosage.

Blue glass chippings for garden

Natural Inorganic Mulch

Of course, there are many natural solutions which are as durable and usually more beautiful than the alternatives. Using slate mulch or gravel can be an excellent way to suppress weeds while at the same time making your borders and beds look orders of magnitude more stunning. They are also very low maintenance. However, using stone or gravel in areas with high temperatures could potentially cause overheating and harm your plants, so it's something to you also keep in mind.

Ultimately, it is important that you select the appropriate type for your specific needs and avoid using it where ever you can identify the potential for risks to outweigh the benefits.

Plum slate chippings in a planter. Jpg

How To Apply Gardening Mulch

How to apply mulch in the right amount will always depend on your goals and the specific needs of your garden, as well as the type of material you use. When to mulch garden beds is also a key factor to consider. Let's look at application, next.

Using Organic Mulches

There are a few considerations to bear in mind when applying organic mulches. The first is to avoid placing it too close to the trunks of trees or shrubs, as this can attract rodents which may gnaw your plant's bark and also lead to rot from excessive dampness.

Secondly, it should be replenished as it decomposes and incorporate into the soil. It's suppresses weeds best when it is applied in thicker layers, naturally. For example, a layer of wood chips or shredded leaves should be about 7.5cm - 10cm (3-4") thick, while grass clippings and compost can be applied in a thinner layer of 2.5cm - 5cm (1-2").

Heavy duty weed membrane on grass

Another consideration (which is a personal bugbear of mine) is the potential for weed seeds, and occasionally chemicals, to be present in animal manure. Rotted horse manure is one of the classic mulches you will find problems with. Even when you seek a heat-treated compost, that has been heated to high temperatures to kill off unwanted seeds or pathogens, you can still be unlucky enough to receive a garden full of nettle and lucerne grass within a month of laying it upon your garden beds.

In order to minimise this risk, it is always advisable to seek the soil specification sheet which will show the testing and compliance data. If the suppliers don't make it available, then it's probably worth looking elsewhere. You may also use materials like pine needles, which are less likely to contain weed seeds and can be freely available.

Utilising Inorganic Mulches

In utilising inorganic mulches, remember to maintain a 5-10cm (2-4") depth for effective weed control, use a weed membrane with loose fill products and regularly water your plants. Unlike organic types, they don't enrich the soil over time but can be excellent at conserving moisture.

Bark mulch around spring bulbs and shrubs. Jpg

Also, it's worth keeping in mind the impact they will have on soil temperature, as inorganic mulches work in different ways. Darker materials absorb heat, keeping the soil warmer, and sometimes overheating it, whereas lighter materials can reflect sunlight and keep the soil cooler.

As with all mulches, choosing the right one should depend on factors such as:

  • installation issues and how much maintenance you are prepared for;
  • compatibility with your other gardening goals and plants;
  • initial costs; and,
  • the environmental impact, especially as it pertains to your local climate.

Need to work out how much mulch your project needs? Use our free bark calculator.

What To Use As Mulch?

In this section, we are going to look at the various types of materials that can be used for mulching plants and around your garden in general, so that you can decide which is the material for your mulching needs. We cover woodchips and shredded leaves, grass clippings, compost, straw and hay, plastic and rubber mulch, landscape fabric and stone mulches.

Leaf mold breaking down into compost

Wood Chips and Shredded Leaves

For many reasons, the combination of wood chips, bark and shredded leaves remain in the most popular option for mulching. Apart from being very economical and easy to get, they are versatile and can be suited to a wide range of garden types and situations, adding a natural and timeless look to garden borders and beds. Further, tree shredding with the help of a domestic shredder can make mulching large quantities of leaves and green matter a breeze, and provide free mulch.

However, the combination of wood chip mulch and leaves might not be the ideal one for every situation. For example, they might not be the best choice for vegetable gardens or annual flower beds. The presents can hinder digging and replanting in the beds as they aren't that quick to fully breakdown. This is perhaps one reason why straw, or compost that is well broken down, is preferred for this type of job.

Despite this, they still offer great value as a mulch. In order to use them most effectively for suppressing weeds and retaining moisture, ensure you have applied a thick enough layer.

1ornanmental bird bath in a garden. Jpg

Nitrogen-Powered Grass Clippings

Despite being disposed of (for the most part) in the green waste bins of most homeowners, garden lawn clippings can offer significant benefits to your vegetable garden. They are a rich source of nitrogen, and will also help retain moisture control weeds as they break down into the soil. Just place it on the bare soil of you garden bed, as you would any other mulch, and allow it to break down over time.

It is best to avoid using treated grass as mulch because it usually will contain chemicals that are harmful to your plants and can contaminate the soil. It can also be quite handy to mix grass clippings with other materials such as fallen leaves or old mulch, which will help to provide aeration and reduce the chance of getting a 'wet mulch'.

1fresh cut grass clippings for garden bed

Compost Mulch

Straight from your compost bin, this mulch is rich in nutrients, and is a well-regarded and commonly used soil amendment that can significantly improve your gardens growth and general health. It performs all of the tasks that we have previously covered about mulches, however, it is worth mentioning that compost mulch should not be the only mulching option used.

For best results, it should be laid beneath a different type of mulch, such as wood mulch or decomposed leaves, to add the benefits of protecting roots and maintaining soil temperature, which compost alone is not as successful at doing.

To use compost mulch effectively, use these steps:

  1. 1
    Apply a thin, 2.5-5cm (1-2") layer of compost to your garden bed.
  2. 2
    Follow with a thicker layer of another mulch, such as wood chips or pine needles. Use a depth of between 2.5-7.5cm (1-3") on top of the compost.

This combination will help to retain moisture, suppress weeds, and provide adequate root protection, as the compost breaks down over time, enriching the soil.

1dig in the ground home compost bin

Straw and Hay For Veggies!

What does mulching mean for your veggie patch or allotment? Well, straw mulch can be the difference between good crops and a great harvest. Straw and hay can perform all of the tasks of any good mulch, with the additional benefit of providing a protective barrier that prevents soil erosion while keeping fruits and vegetables clean and less susceptible to soil borne diseases.

It is important to distinguish between straw and hay mulch, at this point. In general, straw is recommended over hay, because it is less likely to contain weed seeds or be contaminated by pesticides. If you are seeking a weed free garden dad, choosing seed-free straw, such as salt hay straw or wheat straw, will help to minimise the risks.

Applying straw and hay straw mulch, effectively, is fairly easy. Place a thick layer over your vegetable beds, being careful to keep it away from plant stems. This is in order to discourage slugs and rodents from congregating around the all-important pipeline to your fruit and vegetable plants.

1mulching young herbs with straw. Jpg

Plastic Mulch

Plastic mulch is far from a conventional choice, especially around your home and garden, but it does also have some benefits. It is particularly good at retaining moisture and warming the soil surface, which is useful in colder climates and for heat-loving plants. On a more commercial scale, it is excellent at suppressing weeds and often used to keep fruit off the ground to prevent rotting.

However, it requires careful usage, as poor installation or removal can damage plants and contaminate the soil. Further, it adds nothing to soil health, rather, it can be a very effective barrier that hinders the vital exchange of nutrients water and air with the soil.

To use plastic mulch effectively:

  1. 1
    Form raised beds and roll the plastic sheet out on top of the soil surface.
  2. 2
    Make holes in that plastic before transplanting seedlings through the plastic holes.
  3. 3
    Keep in mind that any other soil improvement or mulching will need to be planned ahead for an executed prior to laying the plastic mulch down.
  4. 4
    The plastic sheeting will need to be anchored down with pegs and other heavy items, particularly in windy regions.

To minimise the level of contamination from the plastic, be sure to remove at the end of the growing season and recycle the plastic responsibly.

1rows of shallots in a plastic mulched garden bed

Rubber Mulch

While rubber chippings have their place in providing safety for play surfaces and equestrian arenas, as a mulch on your garden, it really is a tough sell, in our opinion.

Rubber mulch which is often marketed as a long-lasting, durable alternative to traditional organic mulches, is not immune to deterioration. Factors like fungal infestation is, bacterial degradation and exposure to UV are all reported to impact on both it's medium to long-term appearance, and it's functionality.

Due to the fact that it is manufactured from recycled rubber tyres, it contains potentially very harmful compounds, which can leach into the environment. Its lack of organic matter can also lead to soil health issues and water runoff problems. The claim that they facilitate natural drainage is also very questionable, because it can lead to the clogging of the membrane installed beneath which will impede proper drainage and can result in the pooling of stagnant water.

1recycled black rubber edging around a mulched garden. Jpg

Landscape Fabric

Due to its ability to stop weeds while allowing air and water to pass through its permeable surface, landscape fabric is a fairly popular choice for mulching with a low maintenance goal in mind. Although, landscape fabric should be avoided near shrubs, where their roots and weeds, such as blackberry, may grow into the fabric and become very difficult to remove.

But it, too, is not without its limitations. It does degrade over time, and is very difficult to remove from the soil. To slow down that process, it is advisable to cover it with a second mulch topping, which should prolong its life span. This is akin to installing a weed membrane under mulch.

1planting a variegated shrub into weed control fabric mulch

Stone Mulches

Stone mulches can be an excellent choice for certain garden applications. Generally made from small rocks, slate chippings, pebbles or gravel, they can be used to suppress weeds whilst transforming the look of your borders and beds, whilst significantly reducing the amount of maintenance required. Particularly suited to xeriscaping or low-water landscape designs, they don't retain water like organic matter, nor do they ever break down, making them the longest lasting and possibly most cost-effective option available.

Stone mulches can absorb and reflect heat, potentially warming the soil in colder climates or overheating plants in hot, sunny conditions. Therefore, they are best used around plants that can tolerate such conditions.

For instructions on how to install landscaping fabric, or use stone mulching, here is our article about How To Lay Slate Chippings.

1miniature daffodils growing in garden gravel. Jpg

Mulching Techniques

The success of your mulching can depend on your technique and choices for the specific situation. Here are some of the basics:

  • Always weed the area first, as this will prevent the mulch from simply providing a fertile and optimal home for existing weeds.
  • Apply a thick layer of mulch – about 7.5-10cm (3-4") for most types – to effectively stop weeds and maximise soil moisture.
  • When using a combination of mulches, such as compost and wood mulch, apply the compost in a thin layer first.
  • Remove winter mulch from perennials and bulbs in the spring to allow for quicker growth and in order to prevent rot.
  • Always keep mulch away from the crown of plants, their stems and trunks to discourage bark-gnawing animals and the potential for rot.
1mulching with landscaping bark


Another useful technique in mulching is called double-mulching. This method involves placing a layer of brown packing paper or cardboard beneath your primary mulch, creating an additional barrier against weed growth. Double-mulching can be particularly useful in areas with stubborn perennial weeds or where a more permanent weed control solution is desired.

2double mulching with brown packing paper


In conclusion, mulching is an essential aspect of gardening that mimics the natural life-cycle of pristine and well-established ecosystems. While there are some aspects about certain materials that need to be kept in mind when used with particular types of plants, by understanding the types, and their pros and cons, you will be able to make informed decisions about what is the best mulch for your needs, or even just a specific plant pot, and keep your plants in top health!

No matter what type of mulch you choose, when you follow best practice mulching techniques, your success in the garden, and the health of your plants, is sure to be on the improve. So, go ahead now, and harness the magic of mulch.

2pink and yellow scottish heather. Jpg

Frequently Asked Questions

What is the best mulch for flower beds?

While the best mulch for your flower beds really does depend upon the specific needs of your plants and your own preferences, a versatile option that suits most types of flowers is shredded bark mulch. It is an eco-friendly, sustainable product with slow decomposition that can add great texture and a natural contrast for your flowers and planters.

However, the circumstances need to be weighed up when you are mulching acid loving plants such as azaleas or rhododendrons. Whilst rhododendrons are not native to the UK and can be quite a pest (in spite of their beauty), if you are growing them you should look for and acidifying mulch, like pine straw or needles.

In climates that experience extremely hot and dry conditions, may need to install a membrane with your mulch, or go for something like gravel or rocks, in order to conserve the maximum amount of moisture possible.

What is mulch for the garden?

Applying mulch is a key, cyclical element in gardening that serves various functions. It is a layer of material, either organic or inorganic, applied to the surface of soil. The layer conserves soil moisture, improves soil fertility and health, reduces weeds, and adds a decorative appeal to the bare soil.

Is mulch the same as compost?

No, mulch is not the same as compost. They are different products, with mulch used on the top layer of soil to protect plant roots, control weeds, retain moisture and regulate temperature, and compost used beneath the top layer of soil to provide essential nutrients to the soil.

Is mulch the same as bark chippings?

Mulch is a layer of material applied to soil for various purposes, such as conditioning and discouraging weed growth. Organic mulches can include garden bark chippings, shredded tree bark off, wood chippings, wood shavings, and compost. Bark chippings are a very popular form of mulch.

What do you use mulch for?

Mulch is used to help soils retain moisture, reduce watering, suppress weeds, improve soil organic matter, provide nutrients, deter some pests, warm up the soil in spring, and protect plant roots from extreme hot and cold temperatures.

What are the disadvantages of mulching?

Mulching can be detrimental to other plants in the garden as it can bury and suffocate plants, provide a hiding place for pests, and cause excess heat when done incorrectly. This can also prevent some seeds from germinating, so it's important to wait until plants green up before mulching.

What are the benefits of using organic mulch?

Organic mulch provides numerous benefits to add nutrients to your soil, such as improved structure, additional nutrients, and enhanced plant growth. We go into greater depth here.

There are many wonderful types of wood chippings products available for your play area or mulching needs. Check them out!

About the author 

Ben Parrot is a landscape gardener and amateur geologist. He is the founder of Outdoor Aggregates, with the mission to create the first encyclopaedia for decorative aggregates. From natural stone through to decorative bark, these aggregates are critical to garden and landscape design, universally.

The problem: There isn't any place where all the different types of decorative landscaping materials and construction aggregates can be found, nor are the specifications of each type readily available. So, enriched by his extensive experience, and inspired by the timeless elegance and raw beauty of stone and rock, etched by nature's artistry over millennia, Outdoor Aggregates was born.