When applied correctly, mulch has the following beneficial effects on plants and soil:
Mulches prevent loss of water from the soil by evaporation.
Mulches reduce the growth of weeds, when the mulch material itself is weed-free and applied deeply enough to prevent weed germination or to smother existing weeds.
Mulches keep the soil cooler in the summer and warmer in the winter, thus maintaining a more even soil temperature.
Mulches prevent soil splashing, which not only stops erosion but keeps soil-borne diseases from splashing up onto the plants.
Organic mulches can improve the soil structure. As the mulch decays, the material becomes topsoil. Decaying mulch also adds nutrients to the soil.
Mulches prevent crusting of the soil surface, thus improving the absorption and movement of water into the soil.
Mulches prevent the trunks of trees and shrubs from damage by lawn equipment.
Mulches help prevent soil compaction.
Mulches can add to the beauty of the landscape by providing a cover of uniform color and interesting texture to the surface.
Mulched plants have more roots than plants that are not mulched, because mulched plants will produce additional roots in the mulch that surrounds them
WHERE TO USE MULCH
Mulching is a very important practice for establishing new plantings, because it helps to conserve moisture in the root ball of the new plant until the roots have grown out into the surrounding soil. The growth rate and health of trees and shrubs increases when there is no competition for water and nutrients from weeds. Mulch also helps to prevent tree trunk injury by mowers and trimmers. Mulch entire beds of shrubs, trees, annuals, herbaceous perennials and ground covers.
Mulch can also be used to cover trails, driveways, and play and natural areas.
WHEN AND HOW OFTEN TO MULCH
The best time to mulch new plantings is right after you plant them. Around established plants mulch is best applied in early spring. This is when plants are beginning to grow and before weed seeds start to germinate.
HOW DEEP TO APPLY MULCH
The amount of mulch to apply depends on the texture and density of the mulch material. Many wood and bark mulches are composed of fine particles and should not be more than 2 to 3 inches deep. Excessive amounts of these fine-textured mulches can suffocate plant roots, resulting in yellowing of the leaves and poor growth.
Coarse-textured mulches such as pine bark nuggets allow good air movement through them and can be as deep as 4 inches.