Yes, you must remove all existing weeds before laying down a weed barrier, also known as landscape fabric. This permeable material, typically made of synthetic fibers, suppresses weed growth by blocking sunlight and preventing new seeds from germinating. It is not designed to kill established plants. Skipping the removal step will cause the barrier to fail quickly, leading to a maintenance nightmare where weeds become nearly impossible to remove.
Why Pre-Installation Removal Is Mandatory
Leaving established weeds underneath the barrier severely compromises its effectiveness because these plants have stored energy reserves in their root systems. Tough perennial weeds, such as bindweed, thistle, or nutsedge, possess deep underground structures like rhizomes or tubers. These root systems allow the plant to persist through unfavorable conditions, like a lack of sunlight, and they will continue to push upward.
Trapped weeds will attempt to grow horizontally or exploit any small gap or seam in the fabric, eventually emerging at the edges or through cuts made for planting. Some weeds will exhibit etiolation, growing pale and weak as they search for light, but they will still push against the fabric until they find a way through. If a weed anchors its root through the woven material, pulling it out often tears the fabric or leaves a portion of the root behind to regenerate.
Furthermore, any plant material left on the ground will decompose over time, turning into new soil material directly beneath the fabric. This decomposing organic matter creates a new medium where airborne weed seeds can land on top of the fabric, take root, and grow down through the barrier. This process reverses the barrier’s function, making the weed problem worse. The entire area must be cleared of all organic debris, including roots and fallen leaves, to prevent future soil buildup.
Effective Weed Clearance Methods
Achieving a completely cleared surface requires eliminating the entire plant, especially the root systems of perennial varieties. For smaller areas, manual removal is highly effective, but requires careful attention to remove the entire taproot or all fragments of rhizomes, which can regenerate from tiny pieces. Tools like a specialized dandelion weeder or a garden fork can help lift deep-rooted plants without snapping the root off at the soil line.
For larger, heavily infested areas, non-chemical methods like solarization or smothering provide a comprehensive solution for killing both weeds and dormant seeds. Solarization involves covering the area with clear plastic sheeting for several weeks during the hottest part of the year, superheating the soil to lethal temperatures. Alternatively, you can briefly use a non-selective herbicide, such as glyphosate, on established weeds. Strictly follow the label instructions and allow the recommended waiting period—often one to two weeks—for the chemical to fully kill the root system. The goal is to ensure the plant is entirely dead before the fabric is laid down.
Proper Installation Techniques for Maximum Suppression
After the soil is completely cleared of weeds, debris, and sharp stones, the ground must be raked smooth and level. This ensures the fabric lies flat against the soil, eliminating air pockets and gaps where weeds might try to grow or water could collect. Once the area is smooth, unroll the landscape fabric, making sure to avoid stretching the material.
When covering a large area, overlap all seams by a minimum of six to twelve inches to prevent weeds from growing through the joints. Secure the fabric to the ground using U-shaped landscape staples or pins, placed every few feet along the perimeter and all overlapping seams. For areas with existing plants, cut an X-shaped slit into the fabric and tuck the flaps neatly around the stem base to minimize exposed soil.
The final step is immediately covering the newly installed fabric with a thick layer of mulch or gravel, ideally two to three inches deep. This top layer protects the fabric from ultraviolet (UV) light degradation, which breaks down the material over time. The weight of the mulch also helps hold the fabric securely in place, completing the weed suppression system.