Robert Balek: Mulch much?

Adding mulch to your garden and landscape is the most often recommended way to reduce weeds, improve soil, reduce water requirements and improve the environment.

There are many kinds of mulches available and many reasons to use mulch, but not all mulches are created equal, and not all do the same thing.

And, like anything else, there is a right way and a wrong way to use it.

Mulch works only when the right kind of mulch is used and applied in the proper way at the proper time.

There are three main types of mulch.

Natural mulches are made from renewable natural products like wood chips, shredded bark, straw, leaves or grass clippings. These materials decay and release organic matter and nutrients into the soil.

Natural mulches are easy to find, lightweight, easily spread and relatively inexpensive compared to other mulches. However, natural mulch materials can easily blow away or wash out of the planting area. They also decompose rapidly.

To get the most advantages from your natural mulch, apply it in winter or spring before weeds sprout. If weeds are already sprouted, remove them from the soil surface before spreading mulch.

Apply natural mulch materials directly onto the bare soil surface after weeds are destroyed or removed. Be sure to use a thick layer of at least 5-7 inches to prevent weed seeds in the soil from sprouting. Additional mulch can be added as the layer depletes.

The biggest mistake in using natural mulch is to use a landscape fabric under it. The fabric traps decaying mulch particles and other natural materials, making a fertile seedbed for new weeds to sprout. Eventually, weed populations can be as numerous as with no mulch.

Because of their light weight and washability, natural mulch materials easily blow or wash away when placed on landscape fabric, exposing the fabric and ruining the desired aesthetic. Avoid landscape fabric under natural mulches.

Dyed mulches eventually fade, and rainwater runs through them releasing chemical dyes into the soil. Natural wood mulch does not pose that issue.

Rock mulch is natural but is not renewable. To use rock mulch, it is advised to use a landscape fabric on top of the soil before spreading the rock. The fabric prevents soil from working its way up between the rocks where weeds can grow. To keep the mulch in place, installation of a thick, sturdy edging is recommended on landscape beds where rock mulch is installed. Rock mulch is heavy to install but is much less likely to blow or wash away, remaining in place for many years. Colors and sizes can be selected to compliment the landscape.

White rock mulch is not advised because the reflectivity of the color can burn sensitive plants. Similarly, black rock mulches retain heat which can harm roots. Because of its relative permanence, rock mulch is not recommended for gardens where cultivation will occur, such as for vegetables, flowers, and fruits.

There are rubber mulch products available. These products are sourced from old rubber tires which have been shredded into small chunks.

Rubber mulch is lightweight as are natural mulches, blowing and washing away into other parts of the landscape. But rubber mulch does not decay. The bits, although transient in the landscape, remain permanently in the environment, often ending up in lawns, flower beds, and other areas where accumulation occurs.

Black rubber mulch retains heat and can be too hot to handle with bare hands in summer. This heat is harmful to plants and organisms in the environment.

Other environmental concerns include the potential for rubber mulch to release chemicals into the soil and water. Rubber mulch is not advised for landscape use due to these disadvantages.

Robert Balek is MU Extension’s Horticulture Field Specialist for Cassville and the Barry County area