Which Mulch is Best?

Inorganic Mulch: Lava Rock, Marble Chips, Pea Gravel and Crusher Dust

Pros:

Cons:

Does not break down and release organic matter and nutrients back to the soil.
Does not conserve soil moisture.
Does not help provide a micro-climate for healthy root development.
Does not insulate the soil from summer’s heat and winters freezing temperatures.
Does not modify winter freeze and thaw cycles.
Does not contribute to the soils rebuilding process or to biologically active soils.
Underlying soils become compacted.
Rock mulch can and will damage tree bark and girdle plant stems.

Landscape Fabric and Plastic Weed Barriers

Landscape fabric and plastic weed barriers are not recommended for use in landscape plantings for the following reasons:

Landscape fabric creates an interface which can delay water penetration initially and leads to wet low oxygenated soils.
Fine feeder roots grow up through the fabric in search of oxygen when the soil is wet and later become susceptible to drought conditions.
Plastic prevents both water and oxygen from reaching a plants root system.
Both plastic and fabric barriers prevent the return of organic matter to the soil as it decomposes. Organic matter is critical to maintaining soil structure.

Organic Mulch: Woodchips, Compost, Tree Bark, Pine Needles, Saw Dust and Cocoa Hulls

Pros:

Tree roots are genetically adapt to growing in a forest where they are covered by an organic layer of leaf litter and decomposing wood.
Organic mulch breaks down and provides organic matter and mineral elements to the soil.
Keeps soil temperatures cooler during the summer months.
Prevents rapid freeze and thaw cycles from damaging the roots.
Keeps lawn mowers and string trimmers away from the trunk.
Provides a suitable micro-climate that supports other beneficial organisms.
Does not allow the soil to become compacted.

Organic Mulch Concerns:

When organic mulch is applied to the soil surface only, without being incorporated into the soil, it does not rob the soil of a significant amount of nitrogen.
Insect and disease causing micro-organisms have very specific needs in order to survive. Woodchips derived from insect or disease infested trees seldom infect nursery stock.
Termites are not spread through wood chips.

Rules for Proper Mulching:

Mulch should not be applied thicker than 2-3 inches deep.
Mulch should not be built up around the trunk or stems of woody plants.
Avoid mulch volcanoes. Thick mulch around the base of a woody plant can lead to stem decay and stem girdling roots.
The larger the area around a tree or shrub that you mulch, the better off that tree or shrub will be.
For established trees much out to the drip line or one foot for each inch of trunk diameter.
For newly planted trees provide a minimum three foot diameter mulch ring.

Which Mulch Is Best?