Landscape fabric, often called a weed barrier, functions by creating a physical separation between the soil and the open air, denying weed seeds the sunlight necessary for germination. The primary purpose of this material is to suppress existing weeds and prevent new ones from sprouting from the soil below. For the fabric to perform successfully, the preparation of the area is crucial. The answer to whether grass must be removed before installation is a definite yes, as skipping this preparatory step almost guarantees the failure of the entire installation.
The Necessity of Complete Grass Removal
Laying fabric directly over existing grass or weeds quickly compromises the weed barrier’s effectiveness. Persistent, aggressive weeds like Bermuda grass, quackgrass, and nutsedges possess the structural rigidity to pierce through the woven fibers of the fabric from below. These tenacious plants will push through any weakness, including small pores designed for water permeability, negating the entire weed control effort.
Residual grass roots and plant matter trapped beneath the fabric will decompose, creating an uneven surface as they break down over time. This decomposition causes dips and hollows, which can lead to tearing of the fabric when weight is applied or when the material settles unevenly. Furthermore, the presence of dead organic material encourages insects and pests. A smooth, level, and completely clean soil surface is necessary to ensure the fabric remains intact and stable for its projected lifespan.
Practical Methods for Clearing the Site
Homeowners have several effective techniques to completely clear a site of vegetation and eradicate the root systems before installation. These methods range from manual labor to chemical application and heat treatment.
Manual Removal
Manual removal involves using a flat-bladed shovel or a sod cutter to scrape the grass and a few inches of topsoil away. This removes the entire root crown and rhizomes. While labor-intensive, this method provides immediate results and leaves the soil ready for the next step.
Mechanical Tilling
Mechanical tilling can loosen compacted soil, but it carries the significant risk of activating the “weed seed bank” deep within the earth. Tilling brings dormant weed seeds to the surface, exposing them to light and oxygen, which cues them to germinate. If tilling is used, it is recommended to wait a few weeks for the first flush of weeds to germinate, then kill those seedlings before laying the fabric.
Chemical Application
A chemical option involves applying a non-selective, systemic herbicide, such as a product containing glyphosate, to kill the grass and roots completely. These herbicides are absorbed through the leaves and translocate to the root system, killing the plant from the inside out. For full translocation and death of the root system, a waiting period of one to two weeks is required before disturbing the dead vegetation to ensure the treatment is fully effective.
Solarization
For a non-chemical approach, solarization uses heat to sterilize the soil’s top layer. This involves thoroughly moistening the soil, covering it with clear plastic sheeting that is 2 to 6 mil thick, and tightly burying the edges to trap heat. The “greenhouse effect” raises the soil temperature to between 110°F and 140°F, killing most seeds and pathogens within four to six weeks during the hottest part of the year.
Proper Installation for Long-Term Weed Control
Once the site is completely cleared, the soil must be raked smooth to remove any sharp rocks or debris that could puncture the material. The smooth soil base is necessary to prevent small irregularities from causing stress points that lead to tearing. The fabric should be unrolled and cut to fit the area, ensuring that any adjoining sheets are overlapped by a minimum of 6 to 12 inches to prevent weeds from finding a path through the seams.
The fabric must be firmly secured to the ground using specialized landscape staples or pins driven into the soil every 12 to 24 inches along the edges and seams. When planting through the fabric, only small “X” or circular cuts should be made, just large enough for the plant’s base, to minimize exposed soil. The fabric must then be covered promptly with a layer of mulch, gravel, or decorative stone that is at least 2 to 3 inches deep. This top layer protects the fabric from ultraviolet (UV) light degradation, which reduces its lifespan and effectiveness.