Cedar Mulch in the Garden – Uses, Pros & Cons, and Problems

A common tip for gardeners to help keep their soil moist for longer is to ‘mulch over the soil,’ but what does this actually entail, and which mulch is best? The most commonly used mulch is mulch made from chipped or shredded wood, with cedar wood being among the most popular types of wood to use for this purpose.

What makes cedar mulch so beneficial for our gardens? What should we use it for, and maybe more importantly, when should we not use it? Let’s dig a little deeper and find out everything a gardener needs to know about cedar mulch and its potential uses.

What is Cedar Mulch?

Mulch can be made from any organic material which is layered over topsoil to benefit the health of the plants. Mulch is most commonly made from bark or wood chippings, but it can also be made of grass clippings or pine needles, among other things. Cedar mulch is made from the wood of cedar trees, which has either been chipped or shredded. Cedars are evergreen trees that are commonly found in the US, growing in USDA hardiness zones 7 to 9.

How to Use Cedar Mulch in the Garden?

Cedar mulch can be used for various reasons, both functional and aesthetic. Most commonly, it is used for water retention, weed inhibition, soil insulation, improving the look of beds, and repelling insects. Whatever reason you are using cedar mulch for, it is applied in the same way.

Spread an even layer, generally around 3 inches thick, of cedar mulch to the top layer of your soil. Cedar chippings tend to be heavier and are therefore best used around the base of large shrubs and trees. Shredded cedar has a more delicate texture, and its lightweight quality makes it more suitable for use around bedding plants and flowers.

When mulching around the shrubs stems or trunks of trees, you should leave a gap around the outside of the trunk so that the mulch doesn’t actually touch the tree. This is because wet mulch pressed up against the stem or trunk can cause the plant to rot; it also deprives the trunk or airflow, which can encourage disease (Royal Horticultural Society).

Water Retention

Cedar mulch is effective at increasing a soil’s ability to retain moisture. It does this by minimizing moisture evaporation, as it provides a physical barrier between soil and air. It also helps to improve moisture retention by regulating the temperature of the soil, which further aids in preventing water from evaporating.

Wind is another reason why soil moisture can deplete quickly, but a layer of mulch protects the soil from any light winds and is, therefore, able to help the soil remain moist. Having soil that retains moisture is beneficial for a number of reasons. It means that you won’t have to water your plants as regularly because the soil won’t dry out as quickly as it would without mulching. This means your plants can survive longer between waterings, which is great if you are forgetful, or if you are going on vacation or are often away from home.

It will also mean that you use less water to irrigate your plants, as the water which previously evaporated has instead been put to good use. This means a lower water bill for you, and a positive environmental impact as water is not being wasted.

Weed Inhibition

One thing all gardeners have in common is that they loathe weeds! Cedar mulch helps to inhibit weed growth so you can spend less time weeding and more time enjoying your garden. The mulch prevents weeds from taking root in a few different ways. First, the mulch physically protects the soil so that fewer weed seeds will reach the surface of the soil. Second, the mulch acts as a light barrier, preventing sunlight from reaching the soil.

Without light, most weed seeds will be unable to germinate, and therefore will cease to become full-blown weeds. In some cases, stubborn weeds will still make an appearance, but these can be easily spotted against the background of cedar mulch and quickly pulled up.

Soil Insulation

Cedar mulch offers a layer of insulation for the soil, helping it to stay cool in summer and warm in winter. This is beneficial to the growth and overall health of plants, particularly if you live in a climate that experiences extreme seasons. Cedar mulch will help to regulate the temperature of the soil, creating a more stable year-round environment for your plants.

Most plants don’t like to have their roots cooked in the heat of summer, and cedar mulch can help prevent this by essentially shading the soil and keeping it from getting too hot. Similarly, the root systems of plants should not be allowed to freeze in winter, and cedar mulch is able to help with this by insulating the soil, preventing snow or frost from coming into contact with the soil, and holding onto any remnants of heat that exist beneath the layer of mulch.

Attractive Beds

An added bonus of cedar mulch is that it makes flower beds and borders look neat and attractive. The color of cedar wood can vary, but it tends to have a red or orange hue, which contrasts beautifully against green foliage and helps the plants to stand out. It also gives a uniform look to a garden that many people appreciate. Cedar mulch also has a pleasant scent, which adds further attraction to a garden.

Bug Repellent

Cedar wood naturally repels insects, which is why it is a desirable type of wood for use in bedroom furniture, as it resists mite infestations and does not attract moths. This is great for use around the base of plants if you have an insect issue in your garden, or are trying to prevent pest problems, as cedar mulch can act as a natural pesticide.

Long-Lasting Beds

Cedar mulch takes a long time to break down, which means if you use cedar mulch to top dress your soil, then you shouldn’t need to replace it again for many years. Other mulches, such as grass clippings or straw, will break down much more quickly and need to be replaced every year.

If you prefer to invest in longer-lasting garden solutions, then cedar mulch is a safe option. As an added bonus, when cedar mulch does eventually break down, it releases nutrients into the soil.

Pros and Cons of Cedar Mulch

When Not to Use Cedar Mulch

Cedar mulch will offer benefits to most gardens, though in some instances, it may not be the best option. Consider looking for an alternative mulch, or avoiding mulching entirely, if these situations apply to you.

Fragrance Allergies

If you or anyone among your circle of family and friends suffer from fragrance allergies, then cedar mulch should be avoided. It gives off a scent, which is considered pleasant by most people, but some people are sensitive to smells, and it can cause them to have an allergic reaction. Many places of work now have a scent-free policy because of the increased awareness of this issue.

Reactions that might occur if people are sensitive to the smell of cedar mulch can include sneezing, watery eyes, running nose, and skin irritations.

Acidic Soil

Cedar mulch can have an effect on the pH level of your soil. If fresh cedar mulch is used, it can leach very small amounts of acid into the soil, which ordinarily will pose no problem and not make any noticeable difference, but if you already have an acidic soil, then it is best to avoid cedar mulch as it could make your acidity problem even worse.

Nitrogen Depletion

Cedar mulch is known to draw nitrogen from the soil during its decomposition process. This happens with all woody plants and can deplete the soil nitrogen levels so that the nutrients aren’t available to feed the plant and help with its growth.

The only soil affected by this is that which is in direct contact with the mulch, typically the very top layer. If this is the case, cedar mulch will not be a problem because it is not interfering with the nitrogen levels low down in the soil where the plant’s roots are. The exception to this is if the mulch gets mixed into the layers of the soil, in which case it can deplete nitrogen levels near roots and have negative effects.

To avoid this scenario, only use cedar mulch around plants that are permanent. Do not use it around vegetable plants, where the soil will be tilled, and the mulch will be worked deep into the soil. As a precaution, you can also add nitrogen-rich fertilizer to the soil to help balance out any disparity (SF Gate Home Guides).

Beneficial Bugs

Though cedar mulch has the attractive quality of being a natural pesticide, this, unfortunately, means that using it will not only discourage pests from setting up camp in your garden, but it will also deter beneficial bugs from taking residence among your plants.

Beneficial bugs help to naturally control the population of pests in the garden, and they also have other benefits, including pollinating your plants to help flowers or fruits develop. Beneficial bugs include insects like ladybirds, hoverflies, butterflies, moths, bees, and parasitic wasps. They control various garden pests, such as aphids, by eating them or laying their eggs in or on them.

If you’re particularly keen on encouraging beneficial bugs to live in your garden, then it may be best to opt for a different type of mulch that does not contain cedar.

Cost

Cedar mulch is marginally more expensive to buy than other types of wood mulch. Though the difference per bag might be quite small, this could really add up if you have a large area to cover. If you’re conscious of keeping costs low, then cedar mulch probably won’t be the most economical option.

You could instead opt for more inexpensive wood mulch or use one which is entirely free. Grass cuttings are often used as a mulch, which you could save up from mowing your own lawn, or ask your neighbor if you could have their grass cuttings. This option would save you money, and also cuts down on waste that might otherwise end up in a landfill.

Boggy Soil

Cedar mulch is a brilliant way to help your soil retain moisture. However, this can cause serious problems for your plants if their soil is already very moisture retentive. Poorly draining soil, boggy soil, or low lying areas where rainwater pools should not be mulched over with cedar mulch. Using mulch on these soils or problem areas would prevent water from evaporating, causing an excess of moisture around the base of your plants and potentially leading to root rot and the plant’s demise. Cedar mulch, and in fact any type of mulch, should be avoided on these types of soils.

Conclusion

Cedar mulch is an organic top dressing for garden soil, which offers multiple benefits to the home gardener. With moisture retention and soil temperature regulation being among its most important uses, cedar mulch is understandably a popular and commonly used type of mulch, especially when you consider how attractive and long-lasting it is.

There are some situations where cedar mulch is not the best option, and these should be considered and applied to your own circumstances before you make your decision about using cedar mulch. In general, it is mostly problem-free, and its benefits far outweigh its drawbacks.