The Pros and Cons of Wood Chip Mulch

Wood chip mulch is often recommended, but what does it actually consist of? Is it good for your garden? Expert Sarah Jay explores the pros and cons of wood chip mulch, and how to use it.

Written by Sarah Jay Horticulture review by Madison Moulton Last updated: August 6, 2024 | 9 min read

Two pieces of gardening tools laying on top of wood chip mulch placed on the ground in the garden

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One of the things landscapers and garden professionals promote regularly is mulch. There are many different types of mulch, such as leaves, grass clippings, straw mulches, bark chips and even compost. But one widely used and sometimes controversial material is wood chip mulch.

Adding mulch along with compost is great for your plants. Still, there are debates as to which organic matter options are best for soil. Using wood chip mulch produces rich soil, as the Back to Eden method touts proudly. But using wood mulch may not be ideal in every situation!

So in this article, we’ll break down the benefits wood chip mulch provides to gardeners. With the right information and the right action, you can incorporate this incredibly useful material into your landscape and boost the growth of your garden.

Types of Wood Chip Mulch

It’s important to know which mulch is available to you and apply the appropriate materials to provide proper nutrients to your garden.

Arborist Chip Mulch

Machine spitting out countless pieces of tree byproduct, churned by the engine and gathered in a metal compartment for various uses — Arborists produce this material after pruning and cleaning up trees.

This material comes from the byproduct of your local tree service or work done by arborists. It can include any part of a tree removed by an arborist or service: berries, branches, leaves, blooms, and even roots.

This is natural, organic matter that has been run through a wood chipper. Sometimes this is old wood, and sometimes it’s fresh wood. It’s also common to find arborist chip mulch available in areas where orchards are prevalent.

Bagged Wood Chips

Rows of white plastic bags filled with tree byproduct with a vibrant brown color in a site with dirt and material in the background — These bags are common in local stores and plant nurseries.

You’ll typically find this at your local hardware store or plant nursery. It is mulched tree matter in two to three-inch chunks. It could be natural and organic, tree matter directly from a lumberyard or a tree service, and it may be wood that has been chipped on a mass scale.

Most of the time bagged wood chips are from trees that have been used in industry, not from fresh and recently harvested wood. But getting these means you’re also getting plastic bags that you’ll be sending to the nearest landfill.

Modified Wood Chips

A person wearing dark brown shoes standing on scattered byproduct of treated or modified material, with a light brown color — This material comes from various sources often treated to protect against pests and to reduce flammability.

These could be bagged wood chips that have been treated to reduce their flammability. They may be treated with pesticides and herbicides which prevent weeds and insects from taking over your garden.

This material is often used in situations where a homeowners association has designated a preferred color of mulch. Sometimes they’re reflective or dyed a particular color. They may contain chemicals as well as organic matter.

Think of any wood chip that has been introduced to some form of additive to prevent disease, weeds, fire, or to colorize it. As before, it’s bagged, which means more plastic for the landfill.

Bark Mulch

A person standing on a truck's bed, shoveling dark brown tree byproduct into a dark colored wheel barrow on a sunny day — This variety has many sources, including byproduct from trees and furniture makers.

Bark mulch is shredded tree bark that comes from varying sources. Most are directly from trees and people who work with trees. Other sources are sawmills and furniture manufacturers, just to name a couple.

It’s an absorptive mulch that comes in flakes. It can often be full of slivers, and it can easily become matted together, but the fine particulate looks great in a garden.

Shredded Wood Mulch

A person wearing gloves holding finely shredded tree material and placing them on a plant's bed to cover soil, while receiving warm sunlight — Finely shredded material is perfect for gardens.

This is the stuff you’ll see in neighborhood gardens. Shredded wood mulch may be dyed, but is usually finely shredded material such as pine shavings. Generally speaking, this is a finer size mulch of about one inch or smaller in size, making it quite visually appealing.

It’s generally a byproduct of lumber and paper manufacturing, and it’s spread to provide an aesthetic uniformity by retaining moisture and blocking out weeds. However, it comes with a drawback: it can sometimes be fine enough to become matted together and can slow drainage slightly.

The Pros of Wood Chip Mulch

Let’s discuss the benefits and pitfalls of wood chips as a source of mulch or compost.

Adds Nutrients

Close-up of a mulched bed with hosta and bright pink hydrangeas growing, appearing vibrant under the sun — This type of fertilizing material provides nutrients to the soil.

In general, wood chip mulch, when applied correctly, can be an excellent source of nutrients for your soil or compost pile. Ask any regenerative agriculture nut, and they’ll tell you wood chips simulate the same process that occurs on the forest floor, one of the richest environments around.

Retains Water

A gardener in black gloves carefully spreads bark mulch around a young pine sapling, illuminated by the warm rays of the sun, nurturing the growth of the delicate plant. — It can hold water well, keeping young plants moist to encourage growth.

Wood chip mulch is a great way to prevent mud development in your garden because of its water retention properties. Filling a muddy patch is a great way to carry out mulching in a natural way. Wood chips also retain water in the soil, and remedy topsoil erosion.

Looks Good

Dark brown tree material cut down and placed on a garden with multiple bushes scattered in the area — Dyed varieties can allow gardeners to coordinate colors with plants in the garden.

It looks great in any landscape, especially if you’ve managed to color coordinate. Some wood chips, like arborist wood chips, can even be free. If you’ve ever spread wood mulch you know it’s a great way to add a dash of pizazz to your landscape that will last for more than just one season. And when it does break down, you’re building rich soil!

Temperature Regulator

Multiple yellow flowers with vivid green stems planted in a garden covered with tree byproduct and fresh leaves receiving direct sunlight — It helps balance temperatures, protecting roots in cold months.

Another great use for wood chip mulch is as a temperature regulator. Throughout the winter months, mulched plants often have warmer root systems, enabling them to withstand colder conditions much more readily. A thick layer of wood chips applied in the fall can be the factor that keeps your plants from severe weather damage.

Pest Control

Close-up shot of a flowering rose bush in a flowerbed with mulched soil. The rose bush produces upright, reddish-green stems covered with small thorns and compound leaves. The leaves are composed of oval green leaflets with serrated edges. The flowers are large, fully double with rich burgundy-purple petals. — Certain varieties have chemicals or scents that deter pests.

Some modified wood chips keep pests out of the garden, allowing regular healthy growth to occur. Some types of mulch, such as aromatic cedar, can reduce pest populations. The aromatic nature of the wood acts as an effective deterrent.

Reduces Weeds

A person using hands to place dark brown tree material on soil near a vibrant green plan with textured leaves and smooth stems — Covering soil with this material prevents weeds from growing.

Adding a layer of wood chips to the ground to cover the soil surface can reduce grass growth around trees or reduce weeds. Shrubs surrounded by a layer of red wood chips can offset grass rather nicely.

The Cons of Wood Chip Mulch

There are a few issues to consider when it comes to working with wood mulch.

Can Reduce Nitrogen

A rounded raised area in a garden with flowering plants and ornamental structures appearing lovely and colorful on a sunny day — This material sometimes alters the soil’s balance, impacting nitrogen levels.

There are concerns that wood chips can pull nitrogen out of the soil. They do reduce the nitrogen level in the top inch or so of the soil, but further down the fertility of the soil is unaffected.

This makes them a great choice for weed reduction, but not great if you’re starting seeds! Don’t mix mulch into the soil, as that puts the decomposing material closer to your plant roots.

Can Cause Trunk Damage

Someone wearing a pink, textured glove holding dark-colored tree material with a garden in the background with various plants — If placed incorrectly, it can cause plant and tree damage.

They can choke plants and trees if they’re not used properly. The term ‘volcano mulch’ is common in referring to trees with a mound of mulch right against the trunk. This style of mulching trees and other plants is dangerous, as it can cause damage to the trunk or plant’s base.

Can Retain Too Much Water

Shredded tree parts appearing dark brown mixed with water, being shoveled with other compostable materials — Plants will suffer if it holds too much water.

Compost and wood mulch together can make water retention too high for some plants and trees. They could experience root rot as a result. Usually, this is less of a problem for larger chip sizes, but it can be an issue in fine stuff like shredded bark or shredded wood chips.

Color Fades

Shredded tree material with deep brown red hue placed on ground with crates and metal pots placed on top containing soil, plans and other gardening supplies — Vividly colored varieties changes hue over time.

Although colorful wood chips will last for more than one season, they do fade over time. For those looking for uniform color, you will regularly need to top-dress to maintain the right shade.

Uncomfortable to Walk On

Close-up of a woman in white gloves mulching the soil with bark chips in a sunny garden. Bark chips, also known as bark mulch, are small pieces of bark derived from various tree species such as pine, cedar, or cypress. — Stepping on huge pieces while barefoot can cause injuries.

Mulches aren’t a comfortable surface for bare feet. Covering the soil surface with sharp material like arborist wood chips or shredded bark mulch may not be preferable to homeowners for this reason.

May Harbor Termites

A yellowish termite sitting in a crevice of tree material with deep brown color and dirt particles scattered all over — It can be a breeding ground for termites.

Termites may find fresh wood chips and want to make their way from that pile to your home. Although they aren’t technically ‘attracted’ to tree mulch, they may find the layer of mulch a good temporary residence, and then move to the wood in your house once the mulch pile reduces.

For this reason, it’s best to keep wood mulch at least two feet from your home. For a lot of people, this isn’t an option as garden beds are placed right near foundations, so you’ll need to keep an eye on it.

Breaks Down Quickly

Someone wearing gloves holding a handful of dark-colored tree material, placing it on plant bed with woody stems and light green leaves sticking up from the soil — Using this option requires maintenance, including regular replenishments.

Mulch breaks down quickly and needs regular replenishment. It takes a lot of energy to do this. Even if you plan to hire a service to spread mulch for you, it can get costly.

Bagged wood chips, modified wood chips, and tree bark need another layer at least every couple of years as they turn from fresh materials into a mix of decomposed waste. As they compost down, they’re improving the soil, but you’ll still need to make sure you top it off regularly.

Treated Mulch Inhibits Seedling Growth

A young plant with reddish stem and vibrant green leaves growing on ground covered with tree byproduct in different shades of brown and gray — It can affect how young plants develop and grow.

Treated or modified mulch may not be the best option for your garden, especially where vegetable production is taking place. For instance, a modified mulch that contains Preen or another herbicide can reduce germination rates near the mulched area, and as a result, you may not be able to start seeds in that location.

Possible Disease Carriers

Red tree material placed in a section of garden divided using light brown beams lying snuggly on lawn with trimmed green grass — The byproduct may carry diseases, depending on where it comes from.

There are concerns about disease being carried by certain types of tree mulch. While good fungi can live in your mulch, disease-causing fungi can too. This is especially a concern with arborist mulches, so it’s best to request mulch from trees free of diseases for your garden’s safety.

Some Only Available By Cubic Yard

A person wearing work clothes pouring shredded tree material from a yellow bag on ground near a big tree planted nearby solid-looking rocks — Suppliers often sell varieties in big batches.

Finally, arborist mulches may only be available in large supplies. Many tree services want to drop off a 10 to 20-cubic-yard truckload all at once, and if you’re in a suburban area, you may find it difficult to handle that sort of quantity. Consider what you need mulch for, and how you want to source the mulch before you make a large purchase.

Where and How To Use Wood Chips

Wood mulch on the soil surface is a great way to mimic the soil of a rich forest floor. But there are right and wrong times to spread mulch. There are specific ways to layer them with compost and correct ways to spread mulch around plants, trees, and shrubs.

Proper Timing

A person wearing gloves patting down tree material at the base of a vivid green plant with distinct leaves with other greens in the background — This material is an additive to the plant’s soil, not a growing medium.

Mulch is not something you want to plant directly into. You should wait to spread it on soil that you have recently planted seeds in.

Wait for your plants to grow before adding mulch as a ground cover. This keeps developing roots open to nutrient absorption. This goes for transplants too. Make sure roots are significantly developed before you add fresh mulch to the soil.

Proper Spacing

Flowering bushes on garden bed near a gray stone path, having tree material laid over the soil organized to cut away from lawn with vivid green grass — Placing the material incorrectly will harm the plants.

One important thing to remember when adding mulch to soil in a vegetable bed or a place where trees, plants, and shrubs live is to avoid mulching directly to the stem or trunk. This not only allows tree, plant, and shrub respiration, but it also gives them a little moat where moisture can collect and be used slowly and gradually.

The reason mulch gets the reputation of nitrogen-stealing has to do with improper applications like volcano mulching. Even if the mulch is organic and from a tree service where a healthy tree is chipped, too close or too much mulch is a recipe for disaster.

Mulches should not be applied to the soil where plants are growing in a layer more than four inches deep. Two inches is the minimum depth. Any less than two inches and weed suppression is not possible.

In areas where you’re trying to prevent plant growth, a layer of six-inch deep mulch is perfect. This prevents weed development and reduces the frequency of replenishing the mulch layer. Six inches is great for pathways, for example.

Proper Sourcing

A pile of big chunks of tree material from various sources, with different shades of brow, to be shredded for gardening purposes — Vet your sources based on the material’s quality and other characteristics.

Make sure you’ve found a good source for mulch. If you want to grow vegetables, green mulch, or some hardwoods like walnut may not be the best option for your situation.

Most vegetable gardeners prefer softwoods like pine that break down easily so they don’t have to worry about improper plant growth.

Hardwood applied in the wrong situation can kill a plant. Some, like black walnut, are allelopathic and can actually reduce plant growth where they’re placed. While black walnut does decompose and the allelopathic conditions subside, it can take a while. Consider the tree species of mulch when you are planning.

If your mulch is purely an aesthetic choice, you may not need to worry too much about the source. But to make your organic gardening easier, ensure the supplier you source from doesn’t include material that contains fungal pathogens or diseases.

Good sources for mulch are often local tree services. However, you can also get it from your local garden center, either bagged or in bulk. Typically, material from a garden center has been steam-sterilized, giving it an extra measure of protection from pest or disease transmission.

Building Soil

Close-up of a male gardener applying a layer of bark mulch to a young blueberry bush in a raised bed garden. — Combine it with soil to create an ideal mix for your plants.

Maybe you prefer to use mulch to build soil. In this case, it can contain green matter, and it can be hardwood. You can lay it in between beds to break down over time, or you can use it as a pathway.

Green wood is great for this purpose as it’s still fresh from chipping, and may actually include some green leaves to provide nitrogen. This will reduce nitrogen loss as it breaks down, too!

Frequently Asked Questions

It depends! Each wood chip mulch has a different use, and each has its own appropriate applications. Organic options like arborist chips are often considered to be the safest for the surrounding ecosystem.

Technically, no. But mulch too close to your home can encourage termites to move into the structure of your foundation. Keep wood chip mulch at least two feet away from your home to prevent this.

If they are used correctly, yes! They’re an excellent source of slowly decaying nutrients that replenish your soil.