Mulch is a protective layer of material spread over the soil, serving numerous benefits for gardening and landscaping. Cedar mulch is a popular organic variety derived from the wood and bark of cedar trees, offering a distinctive option among natural ground covers. Its appeal stems from its appearance, pleasant aroma, and inherent properties that differentiate it from standard shredded wood products. This material is widely used to regulate soil temperature, retain moisture, and enhance the aesthetic quality of garden beds and walkways.
Composition and Available Forms
Cedar mulch is sourced from two main types of trees: Western Red Cedar (Thuja plicata) and Eastern Red Cedar (Juniperus virginiana). The species used often depends on the geographic region where the mulch is processed. Western Red Cedar is valued for its natural resistance to decay, while Eastern Red Cedar is prized for its stronger, more pungent aromatic oils.
The material is processed into several forms, including fine shreds, coarse chips, or a blend of wood and bark. Shredded varieties often knit together, making them less prone to washing or blowing away and offering good coverage. Cedar chips provide a coarser texture and may be preferred for their appearance or use on pathways.
Consumers can purchase cedar mulch in its natural state, which features a reddish-brown hue that fades to a silvery gray over time. Alternatively, some products are commercially dyed to maintain a vibrant color, such as dark brown or red, for an extended period.
Distinctive Functional Properties
The most recognized attribute of cedar mulch is its ability to naturally deter certain insects. This property comes from volatile organic compounds in the wood’s natural oils, primarily a chemical known as thujone. The strong scent emitted by this compound helps to repel various pests, including termites, certain species of ants, and clothes moths.
The pest-deterring effect is most noticeable when the mulch is fresh, as the thujone concentration diminishes over time due to weathering. This natural defense is not a universal insecticide, and its effectiveness against common garden pests like slugs or earwigs is inconsistent. The aromatic nature of cedar may also dissuade some beneficial insects and pollinators from entering mulched areas.
Cedar wood possesses inherent compounds that make it slow to break down compared to softer woods. This durability gives cedar mulch a longer lifespan, often requiring less frequent replenishment than other organic options. Because of this slow decomposition rate, a layer of cedar mulch can remain effective for moisture retention and weed suppression for up to one or two years.
Application and Usage Considerations
When applying cedar mulch, a depth of 2 to 4 inches over the soil surface is recommended. Maintaining this layer helps to block sunlight from reaching weed seeds, moderate soil temperatures, and reduce water evaporation. Keep the mulch material several inches away from the base of plant stems and tree trunks to prevent moisture buildup and potential decay of the bark, avoiding the common “mulch volcano” effect.
A consideration when using woody mulches, including cedar, is the phenomenon known as nitrogen tie-up. This occurs because microorganisms breaking down the high-carbon wood temporarily draw nitrogen from the uppermost layer of the soil. This temporary nitrogen depletion at the mulch-soil interface can potentially slow the growth of shallow-rooted plants, such as annual flowers or vegetable seedlings.
To mitigate the risk of nitrogen deficiency in sensitive planting areas, incorporate compost or a balanced nitrogen-rich fertilizer into the soil before applying the mulch layer. This concern is largely avoided when the mulch is applied around established trees and shrubs, which have deeper root systems extending below the affected zone. The nitrogen tie-up only becomes severe if fresh wood is mixed directly into the soil rather than being laid on top as a surface cover.