Landscape fabric is a permeable material used in gardening to create a barrier between the soil and the open air. Although often marketed as a permanent solution, the fabric does not chemically or physically destroy established plants beneath it. Its function is strictly to suppress future weed growth, primarily by preventing new seeds from germinating and emerging.
How Fabric Suppresses Weed Growth
The primary mechanism for weed control involves blocking the sunlight required for photosynthesis. By creating an opaque barrier, the fabric starves emerging weed seedlings of light, preventing them from establishing themselves above the soil line. This light deprivation is particularly effective against annual weeds, which rely heavily on surface sunlight to begin their life cycle.
The fabric also acts as a physical barrier, preventing weed seeds already present in the soil from pushing through to the surface. While it helps maintain consistent moisture beneath, the lack of light stops the germination process for many dormant seeds. This suppression limits the number of new plants that can sprout.
The barrier must be permeable enough to allow water and air to reach the underlying soil, supporting the health of desirable plants. This permeability is a balance: the fabric must be tight enough to block light but open enough for essential gas and moisture exchange. If the fabric were completely impermeable, it would damage the soil ecosystem and the roots of planted specimens.
Material Types and Permeability
Landscape fabrics are generally available in two main categories: woven and non-woven, each offering a different balance of durability and permeability. Woven fabrics are constructed from interlocked strips of material, often polypropylene, giving them high tensile strength and making them durable against heavy foot traffic or sharp aggregate like gravel. However, this tight weave can result in lower permeability, sometimes causing water to pool on the surface before slowly seeping through.
Non-woven fabrics, including spun or bonded varieties, are made of synthetic fibers that are heat- or needle-punched together, giving them a felt-like texture. These materials generally offer better water flow and are often used in flower beds or under mulch where superior drainage is desired. While more permeable, non-woven fabrics are less durable and can be more susceptible to tearing or penetration by aggressive perennial weeds.
The choice of material should align with the application, as the fabric’s inherent properties directly influence its long-term performance. A heavy-duty woven fabric is better suited for use under a paver or gravel path, while a lightweight, more porous non-woven option is generally preferred in planting beds where drainage is prioritized.
Installation for Maximum Effectiveness
Proper ground preparation is the first step in maximizing the fabric’s effectiveness and lifespan. Before laying the material, all existing weeds, especially aggressive perennial varieties, must be completely removed, and the area should be cleared of sharp debris that could puncture the fabric.
When installing, it is essential to overlap seams by at least six to twelve inches to create a continuous weed barrier. A small gap between pieces will provide a clear path for weeds to emerge, completely compromising the installation. The fabric should be secured firmly to the ground using specialized landscape pins or staples, placed along the edges and every few feet within the body of the fabric to prevent shifting.
For beds with existing plants or for new planting, small, X-shaped incisions should be cut into the fabric using a utility knife. These cuts must be kept as small as possible, just large enough to accommodate the plant’s base, minimizing the exposed soil area where weeds can sprout. Securing the perimeter by folding the edges up against borders or burying them slightly also prevents weeds from growing underneath the sides of the barrier.
Common Reasons Fabric Fails Over Time
Even when installed correctly, landscape fabric’s effectiveness is rarely permanent, often declining significantly after one or two years. The most common cause of failure is the accumulation of organic matter on top of the fabric. Wind-blown dust, decaying mulch, and falling leaves break down over time, forming a thin layer of nutrient-rich soil above the barrier.
Once this new soil layer forms, wind-dispersed weed seeds find a viable medium to germinate and root directly on top of the fabric. These weeds are particularly difficult to remove because their roots often grow down and become entangled in the fabric’s fibers, making simple hand-pulling nearly impossible. If left unchecked, these roots can pierce through the material, creating permanent openings.
Strong perennial weeds, such as nutsedge or bindweed, possess the necessary vigor to push their shoots directly through even heavy-duty non-woven fabrics. If the fabric is exposed to direct sunlight, the ultraviolet (UV) rays cause the synthetic material to degrade, leading to tears and brittleness. Over time, fine soil particles can also clog the fabric’s pores, reducing its permeability and leading to water pooling, which suffocates the soil and the desirable plant roots beneath.