Cedar mulch is a popular landscaping material, valued for its distinctive reddish-brown color, pleasant aroma, and natural resistance to decay. Derived from the bark and wood of cedar trees, it is often seen as a premium choice for its durability and aesthetic properties. While it offers benefits like weed suppression and moisture retention, it also has several drawbacks that can affect the garden environment. This review explores the disadvantages of using cedar mulch in landscape applications.
Higher Initial Cost and Supply Constraints
Cedar mulch generally occupies a higher price point compared to alternatives like shredded hardwood, pine bark, or composted mulches. The cost per bag or cubic yard can be two to three times higher than more common materials, making the initial investment substantial for large landscaping projects.
This premium pricing is partly due to the specific sourcing and processing of cedar wood, which is often in high demand for lumber and other products. Regional supply issues can further inflate the expense, particularly in areas distant from cedar timber production centers. Although the slow decomposition rate means less frequent replacement, the significant upfront expense is a disadvantage for those managing a strict budget. Additionally, cedar’s color tends to fade quickly under direct sunlight, prompting gardeners to refresh the top layer sooner for aesthetic reasons, which adds long-term costs.
Nitrogen Depletion and Soil Nutrient Imbalance
A significant scientific concern with cedar mulch relates to its composition and subsequent decomposition process. Cedar mulch is a high-carbon material, meaning it possesses a high Carbon-to-Nitrogen (C:N) ratio. Soil microbes require nitrogen to break down carbon-rich materials like wood chips. As these microbes decompose the cedar mulch, they consume available nitrogen from the surrounding topsoil, a process known as nitrogen immobilization.
This temporary nitrogen tie-up effectively starves nearby plants of the nutrient needed for healthy growth, which is detrimental to annuals, vegetables, and young seedlings. The effect is most pronounced if the mulch is accidentally mixed into the topsoil rather than laid as a distinct surface layer. While the nitrogen is eventually released back into the soil, this process takes a considerable amount of time due to cedar’s slow decomposition rate.
Formation of Water-Repellent Mats
Cedar mulch can develop into a dense, physical crust on the soil surface, which is a disadvantage for irrigation. As the fine particles break down, they settle and interlock, forming an impervious layer. This compacted layer often becomes hydrophobic, or water-repellent, when it dries out.
When the surface becomes hydrophobic, rainfall or irrigation water runs off rather than soaking into the ground below. This leads to dry soil beneath the mulch layer, wasting water and potentially causing plant stress. Gardeners must frequently monitor the soil and manually break up the crust by raking or fluffing the mulch to ensure proper hydration of the root zone.
Respiratory and Allergenic Concerns During Application
Handling and spreading cedar mulch can present temporary health risks related to airborne particles and natural compounds. Moving the mulch often generates fine dust particles that can irritate the respiratory system. Individuals with pre-existing conditions like asthma may experience coughing, sneezing, or throat discomfort during application.
Cedar wood naturally contains volatile organic compounds (VOCs) and various essential oils, which are responsible for its distinctive aroma and pest-repelling qualities. These compounds can be released into the air during handling, potentially causing allergic skin reactions, such as contact dermatitis, in sensitive users. To minimize exposure, it is advisable to wear a dust mask and gloves when spreading cedar mulch.