The terms “bark” and “mulch” are frequently used interchangeably in gardening and landscaping, leading to confusion about their material and function. While closely related, they are not synonyms. Understanding the distinction is important for choosing the right material for a specific landscape goal. The fundamental difference lies in their scope: mulch is a broad functional category, and bark is a specific, organic material that falls within that category.
Mulch The Broad Category
Mulch is defined as any layer of material applied to the surface of the soil. This layer serves primarily functional purposes, including conserving soil moisture by reducing surface evaporation. Mulch also helps regulate soil temperature, keeping roots cooler in summer and warmer during winter frosts. Furthermore, it acts as a physical barrier that suppresses the germination of weed seeds by preventing light from reaching the soil.
The category of mulch is divided into two main types: organic and inorganic. Organic mulches are materials derived from plant matter, such as wood chips, straw, or compost. These materials decompose over time and contribute organic matter and nutrients to the soil. Inorganic mulches, by contrast, include materials like stone, gravel, or plastic sheeting, which offer permanent coverage but do not enrich the soil structure.
Bark A Specific Type of Mulch
Bark is a specific, organic material sourced from the outer protective layer of trees. It is a byproduct of the lumber and paper industries, making it a sustainable and readily available form of organic mulch. Common sources include pine, cedar, hemlock, and various hardwoods, with the species determining the final texture and color.
Bark is typically sold in several distinct physical forms, each with unique properties.
Forms of Bark Mulch
- Bark nuggets, or chips, are larger, chunkier pieces often chosen for their aesthetic quality.
- Shredded bark is finer and more fibrous, providing better surface coverage and interlocking capability.
- Pine fines are the smallest form, often used as a soil amendment due to their quick decomposition rate.
Performance and Longevity Comparison
The physical structure of bark products gives them a distinct performance profile compared to other organic mulches. Bark nuggets are naturally dense and have a lower surface area-to-volume ratio than finely shredded wood. This allows bark to resist decomposition for a longer period, often lasting one to two seasons longer than shredded wood before needing replenishment. This slow breakdown means bark contributes nutrients and organic matter to the soil at a much slower pace.
Shredded wood mulch, which often includes both bark and inner wood, has a fibrous quality that allows the pieces to interlock. This interlocking structure makes shredded mulch an excellent choice for use on sloped terrain, as it is less likely to wash away during heavy rain. Bark nuggets, being smoother, are more prone to floating or being displaced by water runoff. Shredded mulches can sometimes compact over time, potentially hindering water and air penetration to the soil.
Bark products are often chosen for their uniform and neat appearance in ornamental garden beds. The slower decomposition rate is advantageous when the primary goal is visual appeal and long-term weed control rather than immediate soil enrichment. Conversely, finer, shredded mulches decompose more quickly, cycling nutrients into the soil faster and making them preferable for improving soil health.
Selecting the Appropriate Material
The choice between a pure bark product and a general shredded or composted mulch depends entirely on the intended function in the landscape.
When to Use Bark
When the goal is to establish a long-lasting, visually clean ground cover with minimal maintenance, bark is a practical selection. Bark nuggets work well in established ornamental beds, around mature shrubs, or along walkways where longevity and a decorative appearance are the priority. Their slower decomposition is ideal when avoiding the constant addition of organic matter to the soil.
When to Use Shredded Mulch
A shredded wood or composted mulch is a better choice when rapid soil improvement is the main objective. These materials break down quickly, releasing nutrients and significantly improving the soil’s structure and water-holding capacity. They are best suited for annual vegetable gardens, flower beds that receive frequent planting, or areas requiring immediate organic enrichment. For sloped areas, the interlocking nature of shredded mulch offers superior stability against erosion and runoff.