Cedar Mulch: Pros and Cons of Using It In Your Garden

By Jessica Nolan, Gardening Expert Gardening And Landscaping

Cedar mulch is beneficial for gardens as it helps to keep the soil moist, manage soil temperature, control weeds, and retain nutrients. However, it’s worth noting that cedar mulch, made from the reddish-brown bark and shavings of cedar trees, has some drawbacks. It can be expensive and decomposes slowly. Considering these factors, you might wonder if cedar mulch is the right choice for your garden.

Mulching plays a crucial role in maintaining soil moisture, preventing weed growth, and improving overall plant health. However, knowing the best type of mulch for your garden can be tricky. Therefore, examining the pros and cons of cedar mulch can help you choose the right option.

This article explores the benefits and drawbacks of using cedar mulch in your garden. Additionally, you will learn where and how to use cedar mulch to keep shrubs, ornamental plants, and trees healthy.

What is Cedar Mulch?

Cedar mulch

Cedar mulch is shredded or chipped wood bark from arborvitae trees (thuja) and juniper trees, which are commonly referred to as cedars. This fragrant, natural landscaping material is used as a protective layer on soil. Like all types of mulch, a layer of cedar wood chips helps suppress weeds, retain moisture, and protect plant roots during winter.

Cedar bark and branch chippings generally come from the eastern red cedar (Juniperus virginiana), white cedar (Thuja occidentalis), and western red cedar (Thuja plicata). The shredded bark chips are obtained when cedar trees are processed for timber. Cedarwood bark also contains thujone—an aromatic chemical with insect-repellent properties.

Is Cedar Mulch Acidic?

Cedar mulch is not significantly acidic and does not make the soil acidic. Although cedar might have some acidic properties, the process of breaking it down into mulch, combined with natural composting, tends to neutralize any significant acidity. Consequently, cedar mulch can be used without the worry of notably changing the soil’s pH. This is in line with general horticultural understanding that, while cedar mulch is slightly acidic, it is not acidic enough to significantly impact soil pH.

The Benefits of Using Cedar Mulch

Cedar bark is an excellent mulching method for weed control. Other benefits of using shredded cedar mulch include locking in soil moisture, acting as a natural insect repellent, and helping to improve soil health. Its reddish-brown color also adds aesthetic appeal when used underneath shrubs and in creating walkways between raised beds.

How to Use Cedar Mulch in the Garden

To apply cedar mulch effectively, spread it in an even layer approximately 3 inches (7.5 cm) thick. Cover the soil’s top layer with this mulch under shrubs, around tree trunks, and along garden pathways. Cedar mulch not only beautifies these areas but also naturally repels insects and enhances soil quality.

Let’s look in more detail at how to use cedar mulch in the garden:

Use cedar mulch for perennial plants

Mulching with cedar bark is ideal for spreading around perennial plants. Cedar mulch under perennial trees, large shrubs, and small bushes keep the soil temperature warmer during winter. The thick layer of cedar chippings protects perennial roots from freezing temperatures. Therefore, cedar-based mulch helps prevent flowering perennials from blooming too early in the season.

Using cedar bark mulch in the garden helps to regulate sudden shifts in temperature. Therefore, soil cools in the fall and warms up in the spring at a slower rate. The benefit to your garden is that the mulching technique reduces stress for ornamental perennials, especially in colder climates.

It’s important to note that while cedar mulch helps reduce stress for perennials, it’s not ideal if you require the ground to warm faster. Consequently, it’s best to avoid mulching areas with cedar bark where you sow seeds in spring. Instead, apply the mulch after the seedlings have started growing. This keeps the soil cool in summer.

Cedar mulch around trees

Cedar bark chippings are one of the most natural ways to mulch around a tree. In their native woodland habitats, trees are surrounded by decaying woody material. Therefore, you can mimic a natural woodland environment by mulching around ornamental deciduous or evergreen conifer trees. The mulch not only suppresses weeds and prevents soil erosion but is also heavy enough to stay in place around large shrubs and trees.

When applying cedar bark mulch, be careful not to pile it too high against the tree trunk. Avoid creating a “mulch volcano” – a common mistake where the mulch is stacked too high around the trunk. Leave a gap of 3 to 6 inches between the mulch and the base of the tree. Wet mulch touching the trunk can cause rot and deprive the trunk of needed airflow, which might lead to disease.

Spread cedar bark around decorative shrub borders

Cedar mulch is a striking landscaping option for decorative borders in your garden. The rich reddish hue of cedar mulch brings a natural warmth and vibrancy to an outdoor space. Also, the natural cedar aromas have a fresh scent, helping to create a relaxing and visually appealing atmosphere in your garden.

Use cedar mulch to create walkways between raised beds

Cedar mulch is an ideal ground cover to create weed-free pathways in your backyard. Spreading a 1” to 3” layer of bark between your raised garden beds makes your garden look tidy. Using cedar mulch for walkways also ensures less soggy ground, reducing the risk of mud developing in your garden during rainy weather.

Use cedar mulch in your compost pile

Using cedar bark mulch in compost can be a beneficial way to contribute organic matter to compost. It’s a high-carbon material and helps to balance nitrogen-rich composting materials. Regularly turning the compost pile introduces oxygen, and combining cedar and nitrogen helps decomposition.

It’s good to note that cedar mulch takes longer to break down compared to other organic materials. Therefore, patience is necessary to allow sufficient time for the composting process. However, once complete, you will have a dark, crumbly organic matter that adds plenty of nutrients to the soil.

Use cedar mulch to help moisture retention

One significant advantage of using cedar mulch is its ability to hold moisture in the soil. Well-drained ground that retains moisture is vital for healthy plant growth. This type of soil prevents root rot while allowing plant roots to absorb nutrients.

Here are three ways mulching with cedar bark shavings keeps soil moist:

1. Surface protection: Mulch forms a protective layer on the soil surface. The dense cover of bark chips reduces direct exposure to sunlight and wind. This helps minimize water evaporation, keeping the soil moist for longer periods.

2. Water absorption: Cedar mulch is an ideal medium for absorbing and holding water. During watering or rainfall, the mulch absorbs moisture. It then slowly releases moisture back into the soil. This contributes to a more consistent soil moisture level.

3. Reduced runoff: The mulch layer helps control water runoff and soil erosion. It breaks the impact of rain or irrigation, allowing water to penetrate the soil more effectively instead of flowing away. This reduced risk of water loss to runoff benefits plant roots.

Types of Cedar Mulch Available

Cedar mulch is available in three different sizes that are suitable for various purposes:

Rough-cut cedar mulch: This type of mulch is best for mulching around trees and pathways.
Medium cedar mulch: This mulching medium is ideal for ornamental and perennial and ornamental beds where a lighter type of much is required.
Finely shredded cedar mulch or sawdust: Fine cedar mulch is a good addition to compost to add high-carbon “brown” material to speed up decomposition.

Benefits of Cedar Mulch

Cedar mulch offers excellent longevity and eco-friendliness, enriching garden landscapes in several ways. Its advantages include natural weed suppression, moisture retention, and temperature regulation. It also decomposes slowly, which is beneficial in some landscapes. Additionally, its pungent aroma repels certain insects and is aesthetically pleasing.

Cedar mulch helps to inhibit weed growth

Spreading a layer of cedar mulch in your garden is ideal for preventing weed growth. Mulch from cedars prevents weeds from taking root in several ways. First, the barrier physically prevents weed seeds from reaching the soil’s surface. Second, mulch stops light, preventing weed seeds from germinating.

Of course, some stubborn weeds may still manage to grow. However, it’s easy to identify them against the red-brown cedar mulch. Therefore, cedar mulch is a great way to reduce garden maintenance and weeding.

Cedar mulch improves water retention

Like all types of mulch, cedar mulch is effective in boosting soil moisture retention. The thick organic barrier of wood chips prevents moisture from evaporating from the soil. For instance, the warm sunlight won’t dry out the ground as quickly, and the heavy cedar mulch shields the soil from the wind, which can rapidly deplete soil moisture.

Using cedar bark shavings for mulching means you won’t have to water your plants as frequently during the summer. Ground that is well-drained yet retains moisture helps keep plant roots healthy.

Cedar mulch regulates soil temperature

Cedar mulch acts as a natural insulator, keeping the soil at an even temperature. The insulating layer of cedar bark and chippings prevents extreme temperature fluctuations. It shields plant roots from excessive heat in summer. Then, in winter, it insulates perennial shrub roots against freezing winter temperatures.

Regulating the soil through cedar mulch creates a more stable environment for healthy plant growth.

Cedar mulch controls fungus and bacteria growth

The pleasant aroma of cedar wood and mulch comes from an antibacterial compound called thujaplicin. Studies show that this chemical molecule has strong antifungal and antibacterial activities. Some people suggest that this fungus and bacteria-resistant compound is why cedar mulch takes longer to decompose.

Cedar mulch is long-lasting and decomposes slowly

Cedar mulch decomposes more slowly than other types of mulch, which can lead to cost savings as you won’t need to replace it annually. Additionally, cedar mulch is heavier than other mulches, reducing the chance of it being blown away. However, this slow decomposition also means that cedar takes longer to release nutrients into the soil.

In contrast, mulches such as grass clippings or straw break down much faster and need to be replaced annually.

Cedar mulch is a natural insect repellent

Cedar mulch is popular with gardeners because of its insect-repelling properties. Cedarwood oil contains aromatic compounds like cedrol, thujaplicin, and thujone, which have pest-repelling activity. Therefore, using cedar mulch in your garden can help keep harmful insects and other pests away.

For example, one study into the effectiveness of cedar mulch as an insect repellent found it effective against Argentine ants. Other research suggests that the oil in cedarwood products may help repel ticks. Additionally, some people claim that cedar shavings are effective in repelling mice and other rodents.

Cons of Cedar Mulch

Despite its usefulness in garden landscapes, cedar mulch has some drawbacks. It can cost more than other mulches. Also, it decomposes at a slower rate, meaning it doesn’t leach as many nutrients into the soil. Additionally, it can negatively affect nitrogen levels in the soil, meaning that it is not recommended for your vegetable bed.

Cedar mulch can be expensive

Cedar mulch is a premium product, meaning it can be quite expensive compared to other types of mulch. For example, compared to regular wood chips, bags of cedar mulch can be three or four times more expensive. If you have a large area to mulch, cedar bark shredding may not be a cost-effective option.

Cedar mulch has a slow decomposition rate

Cedar mulch breaks down slower than other mulches. Although this can be advantageous, it doesn’t provide as many nutrients as pine needles, regular wood chips, or grass clippings. Therefore, it’s vital to consider where to use cedar mulch and its purpose. If you’re looking for mulch to provide a soil nutrient boost, cedar is not the best mulch.

Vegetable patches may require a nitrogen boost after using cedar mulch

Cedar mulch can temporarily affect nitrogen levels in the soil, particularly during its decomposition process. This phenomenon is often referred to as “nitrogen drawdown” or “nitrogen immobilization”. In vegetable gardens, where fast-growing plants have high nitrogen needs, it’s often recommended to add a nitrogen fertilizer when using wood-based mulches to offset any potential nitrogen deficiency.

If the cedar mulch is applied on the surface of the soil and not mixed in, the impact on nitrogen levels in the soil is minimal. The nitrogen drawdown primarily occurs at the interface where the mulch touches the soil. However, it’s best to avoid using the bark of cedar trees in vegetable patches when tilling can work cedar shavings deep into the soil.

Cedar mulch can make poorly-draining soil boggy

Cedar mulch is not suitable for spreading on soil that drains poorly. Its moisture retention means poorly-draining soils or low-lying garden areas can quickly become waterlogged. This can severely impact shrub and plant growth, especially garden ornamentals that require well-drained soils.

Of course, it’s best to avoid any type of mulch on soils with poor drainage.

When Not to Use Cedar Mulch

Cedar is not the best mulch option in certain landscapes. Here are a few scenarios when it’s best to use cheaper mulches instead of cedar:

Poorly-drained soils: Avoid cedar mulch in gardens with heavy, clay soil or soil that doesn’t drain well.
Landscaping beds with annuals: Cedar mulch can affect nitrogen availability. Therefore, it’s not recommended for mulching around vegetables or annuals.
Tight budget: If you are gardening on a tight budget, cedar mulch may be more expensive than other types of mulch.
Undesirable aroma: Some people don’t like the smell of cedar mulch. In that case, using a mulch alternative like traditional wood chips is best.

Cedar Mulch: Frequently Asked Questions

Does cedar mulch inhibit plant growth?

When used properly, cedar mulch doesn’t impact plant growth. However, it will stop weedy plants from growing by blocking sunlight and not allowing weed seeds to germinate. Generally, cedar mulch benefits plant growth by suppressing weeds, retaining moisture, and providing essential nutrients as it decomposes.

Is cedar mulch environmentally friendly?

An advantage of cedar mulch is that it’s a natural, non-toxic, biodegradable material without harmful chemicals. Also, cedar mulch has naturally occurring rich, reddish-brown tones without the need for potentially toxic dyes. Mulching landscapes with cedar mulch promotes sustainable landscaping practices. It is also a natural alternative to dyed red mulches.

How often should I replace cedar mulch?

A bonus of cedar mulch is that it only needs replacing every four to seven years. Because of its longevity, mulch from cedar bark is a cost-effective landscaping solution. Therefore, cedar mulch lasts longer than grass clippings, hay, or traditional wood chips.

Is cedar mulch safe for pets?

The chemicals in cedar mulch are generally safe, but it’s wise to monitor pets for sensitivities. Additionally, cedar mulch typically isn’t treated with harsh chemicals, making it a good choice if you have pets in your family. However, cedar’s natural oils and aroma can irritate some animals, so observe their behavior.

Does cedar mulch repel rodents?

Cedar has some repellent properties, but its effectiveness against mice and rats may vary. It contains the chemical compound thujone, which can repel insects and small animals. However, no scientific studies confirm that cedar mulch is an effective rodent control method.

Does cedar mulch attract termites?

Cedar mulch is generally considered less attractive to termites compared to other types of wood mulch. This is because cedar wood contains natural oils and chemicals that can repel insects, including termites. The aroma and the compounds within cedar act as natural deterrents.

However, it’s important to note that while cedar mulch is less appealing to termites, it doesn’t completely eliminate the risk of termite attraction. If termites are already present in the area or if conditions are favorable for them (like moist soil), they might still inhabit the area, although they might be less likely to feed on the cedar mulch itself.

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