Applying mulch around your trees is a simple and cost-effective way to promote better tree health. During rainy periods, mulch promotes better saturation of rain to the roots of the tree. Mulch breaks up rain droplets reducing runoff and erosion.
Another important feature of mulch is its ability to reduce temperature extremes; this is important in climates with hot dry summers, to reduce tree stress. Trees that are temperature or water stressed are more susceptible to insect and disease problems. In cold climates mulch also provides additional protection to the root zone of trees.
Mulch is also important in retaining moisture levels in the soil. Water and nutrients are taken up through fine absorbing roots. Without adequate moisture these absorbing roots will stop growing and start to decline during drought periods. Mulch reduces the effects of dry periods by keeping these absorbing roots moist.
Mulch decomposes over time and adds organic matter into the soil. This helps reduce compaction and allows for better root growth. Mulch also provides humic acid and micro-nutrients to the soil which enhance the growth of absorbing roots.
Water conservation is another benefit of mulching. Mulch helps retain moisture levels in the soil, it reduces the frequency of supplemental irrigation needs. Often people believe that once a tree is established it doesn't require additional irrigation besides rainfall. However, in dry climates, most tree species do require additional water for optimal growth. Water is the single most important factor in the growth rate of trees. Another method of reducing irrigation requirements is to install a soaker-hose on the ground around the tree, prior to mulch installation. By doing this the water stays beneath the mulch so you don't have to moisten everything from the surface.
Arbor mulch is the most beneficial type of mulch that can be applied beneath trees. Arbor mulch is generated from the chipping of tree branches and usually contains leaves, bark, and several sizes of chipped wood material. This mixture provides better insulation and more organic material to the soil as it breaks down. Chipped wood pallets or bark nuggets provide only limited insulation, less moisture retention, and less nutrients to the root zone.
When applying mulch place the material four inches deep out to the drip line of the tree. No mulch should be placed against the trunk of the tree as this increases potential root fungus at the root crown. Mulch should begin 2 feet away from the trunk. For trees that are columnar in form apply mulch twice the width of the drip line. The drip line is the perimeter of the foliage that drips down.
