The most common problem with mulching is applying too much. "Mulch volcanoes" - large piles of mulch around the base of trees - can cause tree damage. Piles of mulch leaning against tree trunks or plant stems can stress tissues and lead to insect and disease problems. Deep mulch can lead to excess moisture causing root rot. Heavy use of certain mulches (such as grass clippings) over an extended period of time can affect the soil's pH level leading to nutrient deficiencies. Mulch piled against the trunks of young trees can create habitats for rodents and other bark-chewing pests and can girdle the trees.
A heavy blanket of fine mulch can become matted and prevent penetration of water and air or fine mulch can decompose into a "potting soil"-like substance that supports weed growth. Anaerobic mulch may give off "sour" pungent odors caused by the build-up of alcohols and organic acids that may be toxic to young plants and trees. Do not apply fresh mulch until the old mulch has decomposed or been removed. Top dressing with new mulch annually to refresh color can lead to unhealthy mulch build-up. Although deep mulch may seem effective in suppressing weeds and reducing maintenance, the associated problems negate any benefits.
Examples:
| Improper mulching known as "Volcano"
| Correct mulch application
|
