Landscape fabric, often called a weed barrier, is a synthetic material rolled out over soil. It is designed to act as a physical barrier to inhibit weed growth by blocking sunlight. Mulch is a layer of material, such as wood chips or shredded bark, applied to the surface of the soil. The central question is whether the fabric should be placed between the soil and the organic mulch layer, a highly debated topic among gardeners.
Reasons People Choose Landscape Fabric
Homeowners often install landscape fabric primarily for immediate and long-term weed control. The material prevents weed seeds already present in the soil from germinating by depriving them of sunlight. This initial suppression offers a quick solution for newly established garden beds.
A secondary motivation is the fabric’s perceived ability to retain soil moisture by reducing surface evaporation. For applications involving inorganic materials, such as gravel or stone, the fabric serves as a separation layer. It prevents the aggregate material from sinking into the underlying soil, which keeps the stone clean and reduces the need for frequent replenishment.
Common Problems Caused by Landscape Fabric
Despite its initial appeal, the long-term use of landscape fabric under organic mulch introduces several problems for soil and plant health. The fabric acts as a physical barrier that prevents organic mulch from decomposing and incorporating into the native soil. This decomposition process is how mulch naturally adds beneficial organic matter and nutrients back into the ecosystem, a process the fabric completely disrupts.
Over time, this blockage leads to a decline in soil structure and fertility beneath the barrier. Furthermore, the fabric’s pores frequently become clogged with fine soil particles and decomposed organic material from the mulch layer above. This clogging significantly impedes the flow of rainwater and irrigation, often leading to dry, water-starved soil directly beneath the fabric while the surface remains wet.
This lack of air and water circulation contributes to anaerobic conditions and soil compaction, inhibiting beneficial soil organisms like earthworms. The most common failure of the fabric is the return of weeds, which germinate in the debris that accumulates on top of the fabric. Once a weed takes root, its roots often weave into the synthetic fibers, making manual removal extremely difficult.
When to Use Alternative Methods
While landscape fabric is generally detrimental in planting areas, it is an appropriate and effective choice in specific, non-planting applications. It should be used under hardscaping projects, such as gravel pathways or patios, where soil health is irrelevant. In these scenarios, the fabric provides a stable sub-base that prevents the decorative material from mixing with the soil and sinking over time, reducing maintenance.
For perennial beds, vegetable gardens, and areas around trees and shrubs, the fabric should be strictly avoided to promote healthy root development and natural soil improvement. The most effective alternative for weed control is applying a thick layer of organic mulch, maintained at a depth of two to four inches. This depth effectively blocks sunlight and smothers germinating weed seeds without preventing water or nutrient exchange.
Another effective alternative to synthetic fabric is the use of a temporary, biodegradable barrier like cardboard or newspaper. When laid down in overlapping layers and covered with mulch, these materials suppress existing weeds by blocking light and eventually break down naturally. The decomposition of cardboard or newspaper adds carbon to the soil, attracting earthworms and improving the soil’s structure.