Does Mulch Affect Plant Growth?

Mulching and Irrigation

• Mulching has many benefits. It reduces surface evaporation and runoff, which can help reduce irrigation needs. Mulching also helps protect soil from foot traffic and erosion. Plant growth is often improved by larger root systems, because plants are better able to effectively use water in the soil. In coarse or sandy soil, addition of organic mulch can reduce loss of water and nutrients, according to West Virginia University Extension Service.

Mulching and Weeds

• Plant growth can be enhanced when weeds are inhibited by mulching. A layer of mulch can prevent weeds from sprouting by blocking light. Weeds that have already sprouted can also be blocked from sunlight by applying mulch, and they eventually die. According to Oregon State University, woody mulches such as wood chip or bark are the best choices for inhibiting growth of weeds. They are most effective on annual weeds.

Other Benefits of Mulching

• Mulching can improve a plant's resistance to diseases, according to Oregon State University. Regularly adding organic matter to soil can help suppress disease organisms. When mulch is tilled into the soil before planting, it may help increase soil fertility, which improves plant growth. Dark-colored materials used as mulch may increase soil temperature, which may encourage emergence of seedlings.

Problems With Mulching

• Although use of mulch is usually beneficial for plant growth, there are certain circumstances in which mulching might be detrimental. For example, while some types of plants benefit from the increased moisture that mulching provides, in other cases excessive moisture might promote pathogens. Mulch that is applied too thickly can lead to water-logged soil. Heavy layers of mulch applied in the fall can attract rodents.

Considerations

• Mulching contains elements that are essential for plant growth, but shouldn't be considered substitutes for fertilizer. Mulch is usually applied in the spring and fall, according to West Virginia University Extension Service. When using materials that have high carbon to nitrogen ratios, such as wood chips or straw, it is necessary to apply nitrogen while mulching.