Mulch Is Habitat For Important Beneficial Insects
While the ladybug may have the biggest repuration as an important beneficial insect in the home landscape, the real players in terms of protecting plants are ants, spiders, and ground beetles. When you have a good population of these voracious pest insect eaters, they will control over 50% of the pest insects that show up on the plants that are mulched. The ants, spiders and ground beetles need that 2 to 3 inches of material in which to live and do their thing. If the ground is bare, they are too vulnerable to their own predators, the songbirds, so they move on to someplace else.
Mulch Inhibits Weeds
Homeowners who use mulch throughout their home landscape spend very little time pulling weeds which compete with plants for soil nutrients and water. A 2 to 3 inch mulch layer will cover the ever-present weed seeds in the soil, blocking the sunlight which they need for germination. Those weeds that grow from seeds dropped on top of the mulch by birds or the wind are easily pulled. The occasional tough perennial weed, such as thistle and dandelion, are more easily dealt with since the soil under the mulch is protected from compaction. A good mulch protects plants from being overwhelmed by weeds which steal their sun, water and soil nutrients.
Mulch Prevents Some Diseases
Fungal diseases often spread to plants, such as roses, by means of water splashing the spores off the hard ground onto nearby plant foliage. A cushion of mulch on the soil reduces or even eliminates splashing and curbs the spread of the disease.
While mulch is not used primarily to prevent disease, ongoing research suggests that organic mulches may reduce the harmful effects of certain soil fungi and nematodes. It also indicates that evergreen needles are as effective as composted bark in controlling several harmful soil fungi, including fusarium. Mixing needles into the soil or using them as mulch destroys these pathogenic fungi first by stimulating chlamydospores, which attack the fungal spores, and then by preventing further formation of these pest spores.
Mulch Shelters Roots and Bulbs
During northern winters, alternating freezing and thawing of the soil often causes it to heave up bulbs, perennials and even small shrubs, seriously disturbing their roots. A 3 to 4 inch layer of winter mulch over flower and vegetable beds and around trees and shrubs, or a pile of evergreen boughs laid over bulb beds helps stabilize the winter temperature of the soil. Mulch will not prevent the soil from ultimately freezing, but it will protect it from the rapid temperature shifts. Winter mulch also reduces freeze damage to roots of permanent vegetable crops such as berries, asparagus, and rhubarb.
Mulch Deflects Equipment Injury
While handsome specimen trees often look their best in the middle of the lawn, they are terribly vulnerable to harm from lawnmowers and weed trimmers. Lawnmowers can seriously damage tree trunks with what is initially a light bump or minor gouge. Seemingly insignificant bark injuries make trees vulnerable to inroads by pests and disease which find access to the inside of the tree through these wounds. It might take 5 years for the tree to die from the insect or the disease, but it is often a lawnmower that is the real cause of death. A protective ring of mulch on the soil around each tree or shrub sitting in the middle of the lawn will protect those plants from such harm.