Minimizing weed growth in garden beds is an issue for all gardeners. There are several weed management practices available, one of which is the use of landscape fabric. The fabric is laid on the soil surface and mulched over, to prevent the germination of surface weeds and weed seeds. The idea of applying what appears to be a relatively permanent solution to stopping weed growth is very appealing. However, there are drawbacks. We will explore the options and present some of the good and not-so-good uses of this product.
What is Landscape Fabric?
There are a variety of landscape fabric products on the market. Agricultural fabric (photo above) is used to hold down weed growth in areas around crop plants. This is a single year use of a plastic product that can make sense to minimize weed growth, albeit in an unsustainable way.
The landscape fabric that is sometimes used as a weed barrier in non-agricultural gardens is typically a woven plastic or a spun polyester fabric. It is marketed using claims of a long-term ability to suppress weeds while allowing air and water to permeate through it, providing a good soil environment for plants. It is sold in rolls at garden centers and is widely used by commercial landscapers. It can offer a short-term weed management solution when installed directly on the soil and covered with an organic mulch.
Does Landscape Fabric Do What It Claims?
The fabric does prevent weed growth for a while and its claims about water and air penetration are valid, initially. The idea that it provides a “forever” weed solution is misleading.
The fabric allows water and air to move through it for a short period, but it becomes progressively clogged with soil particles, diminishing air and water permeability. Eventually some weeds from the soil beneath the fabric will break through and grow anyway. And, weed seeds blowing onto the surface mulch will germinate above the fabric as the mulch breaks down. If the mulch used is the finely ground type commonly used commercially, it decomposes during the first year, allowing surface seeds to grow above the fabric. To make matters worse, roots from surface weeds can penetrate downward through the fabric creating a weed-pulling challenge that can yank the fabric to the surface, creating coverage and appearance issues. In addition, trying to plant through the fabric, which typically requires cutting it with a cutting instrument, is frustrating at best. Finally, the fabric degrades when exposed to the sun, ultimately depositing plastic into the soil.
The photo above shows a bed (from a neighbor’s lot, not mine) that was covered with landscape fabric and then mulched with 2 inches of finely ground hardwood mulch a little less than two years ago. The mulch has decomposed and eroded, exposing the fabric, showing how the surface weed seeds germinated in the remaining mulch and that the roots grew through the fabric into the soil below. The bottom line is that landscape fabric is at best a short term weed deterrent that is cursed with many longer-term issues that make its use in garden beds ill-advised.
What is the best weed control option?
There is no known way to prevent weed growth forever. Weeds are survivors that are tough if not impossible to eliminate. There are practices however that can minimize weed issues if applied carefully and renewed as needed.
There are chemical and herbicidal weed killers available. They can kill weeds but carry other health and environmental drawbacks and are not recommended here. Some more desirable solutions are listed below.
One possibility is to mechanically remove weeds prior to mulching to minimize immediate growth of surface weeds. When covered with a thick organic mulch this practice can help reduce weed generation. I have had success using a stirrup hoe to cut weeds slightly below the soil surface and below the plant crown, most often killing the weed while leaving the organic matter from its roots to decompose in the soil.
A more aggressive option is to use newspaper, a few sheets thick and overlapping a bit, to cover the bed, and then mulch generously on top of it. This provides a short term weed barrier but will ultimately allow air, water and critters to move through to the soil surface. As the mulch decomposes, it will add organic matter and nutrients to the soil. Select the newspaper with some care. Colored printing is ok, but don’t use glossy paper which has too many undesirable components. Rolls of landscape or construction paper are also appearing in home improvement and garden supply establishments as the public desire to keep plastic out of the soil increases.
Single thickness cardboard, overlapped to avoid gaps for weeds to pass through, is another potential weed barrier. It takes longer to decompose than the newsprint but will break down in a year or two. Moisten the ground and the cardboard prior to adding mulch. Be sure to remove plastic tape and labels from cardboard and don’t use any glossy product.
Use of coarsely ground wood chips or arborist waste as mulch provides a longer lasting cover than finely ground wood mulches. When a thick layer is applied (experts typically suggest 3 to 6 inches), it provides protection against extensive weed growth, although it must be supplemented, typically annually, to continue to be successful. Most commercial landscapers seem to use the fine-ground mulch materials that look nice and smell good but decompose quickly and succumb to surface-seed-generated weed growth within the first year. Coarser chips may be viewed as less stylish, but they offer better air and moisture permeability and a significantly longer life.
Other mulch possibilities include pine needles, straw, and shredded leaves. They break down faster than wood chips and have a different esthetic but can help restrain weed growth, especially if a layer 4 to 6 inches thick is applied.
Use of non-organic mulches (plastic and rubber) and rock mulch are not recommended. Covering the surface with organic material that will ultimately break down and strengthen the soil is a far more sustainable approach.
Conclusion
It’s best not to obsess over weeds. We have discussed a couple of simple ways to start a bed without major weed infiltration in the first year, but weed growth is basically inevitable over time. Using paper-based soil covers along with a healthy layer of coarsely ground wood or other organic mulch is a practical way to minimize weed invasions, although it will require regrooming periodically to maintain the bed’s appearance.
In any case, non-organic landscape fabric, while it may start off appearing successful, inevitably causes problems with weed growth, soil condition, and plant health. As usual, adding organic material to the soil provides the best solution for long term gardening success.
SOURCES:
Featured Photo: Weeds and tree shoots growing through landscape fabric. Photo: R Morini
The disadvantages of landscape fabric | Illinois Extension | UIUC
Landscape Fabric | Nebraska Extension (unl.edu)
“The Myth of Landscape Fabric,” Microsoft Word – B&B #17 – landscape cloth.doc (wsu.edu) (Linda Chalker-Scott, Ph.D., Extension Horticulturist and Associate Professor, Puyallup Research and Extension Center, Washington State University)
Putting an End to My Landscape Fabric Nightmare (psu.edu)
Should I use landscape fabric to keep weeds out of my perennial garden? | Extension (unh.edu)
Landscape Fabric: A Good Option for Controlling Weeds? | Gardening in the Panhandle (ufl.edu)
Mulches for Home Grounds – 7.214 – Extension (colostate.edu)
Thank you for this most informative article on landscape fabric. I would like to add one additional point to be considered in using such plastic fabrics on edible gardens. Being made of petroleum products, it occurs to me that these chemicals may leach from the fabric and enter the soil, negatively affecting the soil organisms, and possibly being picked up by the roots of the plants we eat. Hence, such use of the fabric does not sound like a healthy proposition to me. I did use this fabric on my vegetable garden, and stored the fabric over the summer in plastic garbage bags. When I opened these bags in the fall to reuse the fabric, the odor of petroleum products was extremely strong. It is then that I realized it would be best to discard the fabric and instead cover my garden with mulched leaves – a healthier practice!
Paulette W. Royt, Green Spring Gardens Master Gardener