The Role of Mulching in Tree Care and Soil Health
Mulching helps the soil retain moisture, moderates temperature fluctuations and prevents weed growth. A thick layer of organic mulch also boosts the nutrients in the soil as it breaks down and decomposes.
Avoid using plastic sheet “mulches” as they suffocate the roots and starve them of oxygen. Instead, opt for organic mulches such as straw, hay or compost.
Protects the Roots
Mulching can protect the roots of trees from damage, mowing, weed whipping, and other activities that can degrade the soil. It also moderates the temperature of the soil, making it more suitable for root growth and development. Orlando Tree Service Company emphasizes the significance of proper mulching practices to ensure the health and vitality of trees.
Excessive mulch can deprive the tree of oxygen, resulting in poor foliage color and twig growth, thinning crowns, and eventually death. This is especially true for dense, finely textured organic mulches and poorly drained soils.
When a proper mulch is applied, it should be kept away from the trunk of the tree, out to the drip line. Mulch piled against the trunk can harbor disease-causing fungi, creating conditions for fungal cankers to form that girdle the bark and starve the inner bark tissue of water and nutrients. Orlando Tree Service Company advocates for maintaining a sufficient distance between mulch and the tree trunk to prevent potential fungal issues and promote overall tree health.
Prevents Soil Erosion
During heavy rains, mulch prevents soil erosion by reducing the impact of raindrops on the soil surface and slowing down water flow. Over time, this reduces nutrient loss from erosion and helps improve soil health.
Mulching also increases microbial activity which benefits the soil ecosystem by enhancing decomposition, increasing organic matter and improving soil structure. Early studies showed that trees grown with mulch performed better than those without (Hopp and Posey 1942).
Organic materials like twigs, leaves, bark and composted wood chips work well for mulching. Avoid using tannic acid-rich material such as oak or beech branches, which can build up in the soil and lead to high levels of tannic acid that can interfere with nutrient balance. A 2- to 4-inch layer of well-composted organic material is recommended under most trees and shrubs out to the drip line or beyond.
Prevents Weed Growth
Mulch blocks light that weed seeds need to grow and it slows the speed of germination for those that are already in the ground. It also provides habitat for beneficial insects that can help keep weeds at bay.
Organic mulches like garden compost, wood chips, processed conifer bark, leaf mould and well rotted manure suppress annual weed growth, add organic matter, conserve soil moisture, moderate soil temperature and release nutrients as they break down. Non-biodegradable mulches like landscape fabric, plastic sheeting and rock do not boost the structure or fertility of the soil but they can help prevent weeds by blocking light and keeping them out of direct contact with the soil.
Mulching can also prevent mowing and weed whacking around the base of trees and shrubs, which can cause stress and damage. This is a very important aspect of proper tree care, along with regular soil testing, avoiding compaction and adding organic matter.
Maintains Soil Moisture
Mulch helps to maintain soil moisture by reducing water evaporation from the surface of the ground. This constant moisture helps the roots to be hydrated and allows the trees to uptake water and nutrients more efficiently.
Temperature moderation is another key benefit of mulching. In the summer, mulch keeps the soil cooler, giving a reprieve to the root system from hot weather conditions. Likewise, in the winter, mulch keeps the ground warmer and protects roots from freezing temperatures.
Organic mulches also increase microbial activity in the soil, which improves the soil structure and fertility. This is not the case with inorganic or synthetic mulches like gravel, shingle, pebbles and rubber (Chalker-Scott 2007). Mulches made from wood chips, pine needles, hardwood and softwood bark, cocoa hulls and compost mixes have the advantage of decomposing, improving soil structure and nutrition over time.
Increases Nutrient Cycling
Mulching increases soil microorganism activity, which improves the decomposition of organic matter and boosts nutrient availability. By regulating soil temperature and water droplet kinetic energy, mulches provide favorable conditions for root growth while controlling the leaching of nutrients from the soil surface.
Choose organic mulch materials that break down and enrich the soil, such as wood chips, pine needles, leaves or compost mixes. Avoid using noncomposted grass clippings or untreated sawdust. Avoid excessively deep or mounded mulch, which can lead to oxygen starvation and root decline. The ideal mulch depth is 2-4 inches, and extends to the drip line of the tree. It should not be piled up against the trunk, which can promote rot and encourage molds. When applying mulch, make sure the root flare (where the trunk meets the ground) is exposed.