Mulch is applied to the soil surface primarily to retain moisture, suppress weed growth, and moderate soil temperature swings. While all organic mulches share these fundamental benefits, the specific source material—such as cedar versus common forest products—determines the long-term impact and unique advantages. The choice between cedar and regular mulch ultimately depends on balancing specialized functional benefits with horticultural trade-offs and cost.
Defining the Source Materials
Cedar mulch is specifically derived from the bark and wood of cedar species, which naturally contain aromatic organic compounds. This material is distinguished by its light color, fine, shredded texture, and strong, pleasant scent that persists after application. The characteristic aroma comes from natural oils, such as cedrol and thujone, concentrated within the wood fibers and bark.
“Regular” or standard mulch typically refers to a broad category of less specialized, often less expensive, alternatives. These mulches are usually composed of shredded or chipped wood from various fast-growing hardwoods like oak and maple, mixed forest waste, or readily available pine bark. Unlike cedar, these generic materials lack unique natural oils, and their composition can vary significantly, resulting in different rates of decomposition and aesthetic appeal.
Unique Functional Advantages of Cedar
The primary difference between cedar and standard mulches lies in the chemical composition of the wood, which provides distinct functional benefits. Cedar wood contains natural compounds, such as terpenes, that are known to deter certain insects. This natural chemical defense makes cedar mulch appealing for use near homes or in areas where control of specific pests, such as clothes moths, carpet beetles, and some ant species, is desired.
Cedar’s natural oils and resins also make it resistant to microbial decomposition compared to most hardwood mulches. This slow breakdown means cedar mulch lasts longer in the landscape, reducing the frequency of maintenance and reapplication.
Impact on Soil Health and Plant Growth
The decomposition rate of wood mulch directly influences its interaction with soil nutrients, which is a significant factor in plant health. All wood mulches are high in carbon, and the microorganisms that break them down require nitrogen, which can be drawn from the soil at the soil-mulch interface. Because cedar decomposes much more slowly, this temporary nitrogen depletion effect, known as nitrogen drawdown, is less acute or prolonged than with fast-decomposing hardwood mulches.
The shredded, fibrous nature of cedar mulch can create a dense, interlocking layer that resists wind and water erosion, making it effective on slopes. However, this fine, matted texture can also become a drawback. If a cedar layer is allowed to dry out completely, it may form a hydrophobic barrier that repels subsequent rainfall, preventing water from reaching the soil beneath.
Practical Considerations and Trade-offs
A significant practical trade-off for cedar mulch is its higher upfront cost, which is often nearly double that of basic shredded hardwood or mixed forest products. However, the longevity of cedar, which requires less frequent reapplication, can offset this initial expense over several years. This extended lifespan makes it an economically sound choice for gardeners who prioritize low maintenance.
From an aesthetic standpoint, cedar mulch is initially attractive, possessing a light golden-brown or reddish color and a strong, pleasant aroma. Over time, the natural color will fade to a silvery or grayish hue as it is exposed to sunlight and weathering. While fresh cedar sawdust can contain allelopathic compounds that inhibit seed germination, aged cedar mulch is generally considered safe for use in established perennial beds and around mature trees and shrubs.