The term "mulch" implies any material spread on the ground to help conserve moisture, deter weeds, prevent erosion and keep plant roots cooler. Mulch material can be organic or inorganic. When choosing between pea gravel and shredded tire mulch, you should consider several important factors. The type of soil, the steepness of the area to be mulched, sun exposure and the kinds of plants in the area are all contributing factors when making your decision.
Determine the acidity level of your soil by taking a soil sample to your local agricultural center. Shredded tire mulch is not recommended on soil with high acidity because the mulch may contain shredded steel belt reinforcement wires. This metal leeches into the soil and contaminates it. Acidic soils quicken this process.
Observe the bed to be mulched and determine where water runoff flows. If the area is at the base of a hill, under a downspout or anywhere else where water will be flowing, pea gravel is a poor choice. Due to the small, round shape of pea gravel, it is easily washed away or even blown away when the winds are high. Rubber mulch does not float and holds to the ground more effectively.
Consider the mulching location. Areas that are enclosed or receive strong sun exposure should be mulched with pea gravel. Shredded tire mulch emits an odor that increases as it heats up. When the mulch gets hot enough, it releases toxic gases that may cause irritation to the sinuses, nausea and headaches. Only use rubber mulch in open areas, set apart from the home.
Use shredded tire mulch in areas such as driveways, around trees or within a hardscaping design. When mulching around smaller plants and flowers, use pea gravel. Research done at Becknell University has discovered that the leachate from shredded tires contains high levels of zinc. Many plant species absorb toxic levels of zinc, which eventually kills them.
Cover playground areas with pea gravel rather than rubber mulch. Pea gravel is not toxic in any way. It is safe to walk on even if barefoot. Parents have reported children getting splinters from shredded tire mulch.
Calculate the area you want to mulch. Pea gravel is far more compact than rubber mulch. Therefore it will require more pea gravel to cover any given area. Pea gravel is more expensive than rubber mulch, per cubic foot. If cost is an issue and the area is a good choice for rubber mulch, it will be a cheaper ground cover.