Mulch Protects Garden Soil and Plants When Applied Correctly

Mulch is defined as a protective layer applied over soil to retain moisture, suppress weeds and moderate soil temperature around plants. Bare soil in garden beds and borders indicates that mulch should be added.

Gravel and stones reduce weeds and retain some moisture but absorb heat that can scorch plants and roots. Removing gravel later requires significant effort, though it is recommended in fire zones because organic mulches are flammable. Shredded tires should be avoided.

Crumb rubber can contain volatile organic compounds, lead and other heavy metals that remain in soil long after removal. Plastic sheeting presents disposal problems. It eventually reaches landfills and breaks down into microplastics that contaminate soil and groundwater.

Natural materials such as shredded bark, wood chips, straw and pine needles improve soil as they decompose. Arborist wood chips are preferred because they turn into humus on the soil surface and hold moisture longer than other organic mulches. Shredded bark mulch performs similar functions but absorbs less moisture and can wash away during heavy rain.

Dyed mulches are best avoided because the underlying wood may come from construction debris that contains harmful substances.

Three to four inches is the recommended depth for most plants. Mulch should be kept several inches away from trunks and stems to prevent rot from trapped moisture. Volcano mulching, where mulch is piled directly against tree trunks, can suffocate trees over time.

A properly mulched tree leaves the base flare exposed. The best time to apply mulch is after the last frost but before weeds emerge. Early application can trap cool soil temperatures while late application allows erosion and weed growth.