We are always being told that we should use mulch on our garden beds and there are good reasons why this is so. By covering the soil the mulch helps to retain moisture by preventing evaporation and also helps to keep down the weeds. But there are some downsides and using the wrong type of mulch can cause problems. I came across an article by Curtis Adams over on the Houzz website which describes six different materials used as mulch and the benefits and drawbacks of each.

Almost every gardening expert will recommend using mulch around new and existing plantings, but why? Mulch has many benefits in the garden, but it can also cause problems if used improperly.
In nature, mulch forms naturally from fallen leaves, dead grasses and other materials that collect on the ground. This layer of decomposed, or decomposing, material provides a home for beneficial organisms that break the organic materials in the mulch into simpler components that can be used by plants. In addition, this natural mulch provides a cushioning layer that lessens the impact of rain falling on the soil, thus reducing soil compaction and erosion, and improving water absorption. Mulch forms a barrier that prevents evaporation ? helping to mitigate against drought conditions. It also acts as a thermal insulator to moderate extreme changes in soil temperature. Mulch shades the soil surface and blocks seeds that require exposure to light for germination, as is the case with many garden weeds.
Mulches used in the home landscape perform many of these natural functions, some better than others. In addition, mulch also serves as a design element, adding color and texture to the ground plane. Determining the best mulch to use depends on where you are, the type of landscape you are working with and your aesthetic goals.

June Scott Design

In this Los Angeles front yard, densely growing drought-tolerant plants make added mulch unnecessary.
Types of Mulch
Listed here are a number of materials used as mulch, along with what they do well and where they fall short. They are broadly grouped into organic, living or once-living materials, and inorganic materials, which include minerals and synthetic products.
Organic Materials

Living mulch. Living mulch consists of low-growing plants that, once established, form a dense layer of ground cover. It may be a single species or a variety of plants that form an interlocking matrix. This is most like what you would encounter in a meadow or woodland setting. Examples of living mulch plants include sedum, lady?s mantle (Alchemilla mollis), moss phlox (Phlox subulata), golden ragwort (Packera aurea) and green and gold (Chrysogonum virginianum).
Pros: Retains moisture, reduces erosion, allows water permeation, supports beneficial organisms, and offers good temperature control and excellent aesthetics. Weed suppression is dependent on the density of planting.
Cons: Takes time to develop thick growth and requires more maintenance during establishment. It can be difficult to tell the difference between desired and undesired plants (weeds).

Lee’s Oriental Landscape Art

Shredded bark, used in this sloping garden in Maryland, tends to interlock and resist being washed away.
Shredded bark. This is made from the outer layer of trees and is a byproduct of the lumber industry. Properties and appearance vary depending on the type of tree. Trees used for shredded bark mulch include hardwoods, cedar, hemlock, pine and redwood. The types available depend on your location. Coarsely shredded grades last longer but don?t look as nice in some settings as finer grades. Over time, shredded bark breaks down to enrich the soil with organic matter. Read product information carefully since sometimes chipped or shredded wood is dyed and resembles shredded bark mulch.
Pros: Suppresses weeds very well, offers good moisture and temperature control, allows water permeation, and breaks down over time to help build soil and support soil organisms. Aesthetics vary depending on the type and grade used.
Cons: Needs to be replenished on a regular basis (one to three years) and fades over time. Coarser grades can float away, and finer grades can become compacted if applied too thickly.

Gardens By Monette, LLC

The bark nuggets in this Ohio yard complement the outdoor furniture, and set off the seating area from the surrounding beds.
Pine bark nuggets. These are actual chunks of pine bark and are available in a variety of sizes. Larger pieces last longer but have a coarser appearance and a greater tendency to float away or otherwise migrate around the garden.
Pros: Similar to shredded bark, but pine bark nuggets are slower to break down than other wood and bark products, and can hold their color for several years.
Cons: Larger pieces tend to move around in the landscape, it?s more difficult to walk on than shredded products, and it has a coarser appearance.