Proper Mulching Practices
As discussed in “Why Mulch?” the use of an organic mulch can have a considerable impact on your landscapes health. Whether that impact is positive or negative has everything to do with how you apply it.
Use organic mulch, be it leaf litter, mixed wood, bagasse, pine bark, or pine straw.
Use cypress (the myriad reasons why will be discussed in my next post).
Apply mulch to a covered and settled height of more than three inches (see caveats below) in your general landscape. Applying more than three settled inches can inhibit water flow and gas cycling within the soil around standard landscape plants. One significant problem with over mulching around young tress is that the mulch can become more attractive to put roots in than the native soil. This leads to disease, weak and shallow roots, and ultimate a tree likely to fail in a storm.
Apply mulch next to the trunk of tress or stems of plants. Always leave a three inch area between your mulch and the plants in your landscape. Mulching all the way to the base of your plants helps promote disease and pest issues that can severely reduce the life of your plants!
Mulch depth…Caveat 1. With older, well established trees, such as our beloved Southern Live Oaks (Quercus Virginia), mulching from at least the drip line back towards the trunk can be done with up to six settled inches of mulch. This will help reduce compaction from foot traffic and suppress weeds where mechanical removal can damage tree roots leading to disease and stress within the tree. Because these establishes trees exchange gases and liquids with the soil far from the drip line (and natively would often have a significant depth of leaf mulch in the wild) the same concerns with mulching above do not apply, but still do not mulch to the trunk.
Mulch depth….Caveat 2. When mulching a landscape which borders and abuts one’s home or other built structure, mulch should only be applied two inches maximum and should not be applied closer than a foot from the foundation. This will ensure the area near the foundation stays drier which helps keep subterranean termites away from the structure. This also provides an area that is easy to inspect for beginning subduction, a problem for many of our homes especially near Lake Pontchartrain, which could be hidden if mulched to the foundation.
Use shells, stones, or rubber. Not only do these inorganic products not provide all of the soil building and nutrient additions that organic mulch provides, but they can cause soil compaction (leading to plant stress) and are very difficult to garden around. The use of some limestone as well as shells can have a significant impact on pushing your soil’s pH towards the alkaline, and these products all heat-up, reducing water and leading to greater manual water and plant stress.