What Is Mulch?
A mulch is any material, organic or inorganic, that is placed on top of the soil in a garden or landscape. Mulches are one of a gardener’s most valuable tools and an essential component of low-maintenance landscapes.
Benefits of Mulches
Aside from their decorative value, mulches offer many benefits to your soil and plants. Mulch reduces the amount of water lost through evaporation by shielding the soil from the sun’s drying rays. It keeps the soil cooler during the summer and acts as an insulator through the cold winter months lessening the effects of fluctuating temperatures on plant roots which in turn decreases their susceptibility to frost heaving. Organic matter is added to the soil as the mulch breaks down. Increasing the soil organic matter will improve a soil’s moisture and nutrient holding capacity, structure, and drainage. Mulch also encourages the activity of beneficial soil organisms. Weed growth is suppressed by the use of a mulch as is the spread of some plant diseases. Mulched plots are also less prone to erosion.
Organic Versus Inorganic
Organic mulches are derived from natural materials that decompose over time. As organic mulches decompose, they add nutrients and organic matter to the soil and beneficial microorganisms like nitrifying bacteria and mycorrhizal fungi are enhanced while undesirable pathogens -- those that cause plant diseases are inhibited. Increased amounts of organic matter will improve soil tilth and drainage, increase soil moisture retention, reduce soil compaction, and attract earthworms. Because organic mulches decompose, they need to be replaced. Depending on the type of mulch used, replacement intervals vary from one to four years.
Inorganic mulches include stones, geotextile mats and landscape fabrics, and plastic mulches. Landscape fabrics and plastic mulches deteriorate with time and eventually require replacement. Inorganic mulches usually are more tedious to install and may require irrigation because water penetration may be limited. Some inorganic mulches are designed to reflect the sky to confuse and keep insects from landing on plants. Many do not have a natural appearance and are often covered by an organic mulch for decorative purposes.
General Tips for Applying Mulches
Common Mulch Problems
Artillery Fungus: Tiny, cream or orange-brown fruiting structures shaped like cups that contain a small black spore mass are called artillery fungus. The fungus “shoots” the spore mass into the air and it sticks to any surface it hits. The small black spots will be visible on plant leaves and/or home siding, and they are very difficult to remove.
Slime Molds: Slime molds are bright yellow or orange slimy masses reaching a foot or more in diameter. They produce tiny spores, which eventually will dry and blow away. These molds are not a serious problem and can be considered a decorative addition to the landscape. Remove them if you find their appearance undesirable.
Sour Mulch: If a mulch smells like alcohol, vinegar, ammonia, or sulfur it is probably “sour.” The smell is created when a wood-derived mulch is piled high and the inside portion of the pile is deprived of oxygen. This causes anaerobic activity, which creates a build-up of acetic acid in the mulch. The acid build-up is toxic to plants, and if the mulch is spread on the landscape without treatment, the volatile acid will quickly cause plants to wilt and subsequently die. Sour mulch can be treated by spreading it out thinly, soaking it with water, and allowing it to dry. After a few days of airing out, the smell should be gone and the mulch is safe to spread around plants.
Recycled Wood Product Mulches: Some companies recycle discarded wood and wood-based products by shredding them and adding a coloring agent to make them appear suitable for use in the landscape. These commercially produced mulches may decompose faster than natural bark mulches and may contain undesirable substances for use in vegetable gardens and children’s play areas.
TYPES OF ORGANIC MULCHES
TYPES OF INORGANIC MULCHES
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