landscape fabric, a sly antagonist of the garden
Landscape fabric has become an omnipresent feature of conventional landscaping in the U.S. due to its assumed weed and erosion prevention capabilities, but it is necessary to take a step back and consider what it is, as well as its lifespan, impacts, net value, and the alternatives.
There are several types of landscape fabric, but most are made with polypropylene or polyester, which are both forms of plastic. These plastics are petroleum-based (made from oil or natural gas) and break down into microplastics that are persistent in the environment. This persistence is a double-edged sword -- it's great when the designed product is serving its purpose, but it's harmful when
the product reaches the end of its useful life and begins to pollute the surrounding environment as it degrades.
If you have ever worked in a garden (or been in one), there is a high probability that you've stumbled across disintegrating landscape fabric. Most landscape fabric will start to decline after a year, or maybe less. Not only does this lead to the release of microplastics in soil (as aforementioned), but it is also unsightly and very cumbersome to work with. Plus, it is no longer as impervious, leading to deterioration of function. Soon, it will have to be replaced or disposed of, adding to the expense associated with landscape fabric.
Landscape fabric has ecological consequences which can be detrimental for the health of the garden and the organisms that inhabit it:
Earthworms cannot breach the surface, so the fabric discourages them from this area. This means that the soil health of the covered area will decline, as earthworms aerate and fertilize the soil, which fosters the cycling of nutrients and encourages root development.
Natural mulch (fallen leaves, pine needles, etc.) cannot replenish soil nutrients due to the fabric barrier.
Fabric interrupts the exchange of gases which are vital to plant health. Plant roots respire (intake oxygen and release carbon dioxide), and obstructing the soil surface causes an increase in carbon dioxide concentration and a decrease in oxygen concentration, inhibiting plant growth.
Landscape fabric reduces carbon dioxide movement between the soil and atmosphere about 1,000 times more than wood chip mulches do (see resource #5).
Reproduction and spreading of desired plants is limited, as seeds cannot penetrate through the fabric and sprout.
However, weeds, which are highly resilient, often still grow on the surface of the landscape fabric and bore through it with their roots. Weeds often find their way onto fabric via wind, and any mulch or soil on top serves as growing media. (Roots of weeds penetrate the landscape fabric too, making it harder to remove them later on.)
Runoff from storm events cannot infiltrate as thoroughly if fabric is present, resulting in a higher runoff volume and drier soil. (Because the soil is less aerated under these areas, roots are become less drought tolerant, meaning soil dryness will affect the plants more.)
The primary purpose of landscape fabric is to prevent the growth of weeds. Unfortunately, its presumed ability to accomplish that purpose well is misleading, and there are many detrimental consequences for our gardens and the environment at large. When considering that this product also has a somewhat substantial cost and required amount of labor associated, it is probably best to avoid using landscape fabric.
Another common use of landscape fabric is to prevent against erosion by stabilizing soil and/or rocks. The problem of a short lifespan, combined with the fabric bearing a significant load of soil and/or rocks, will result in disintegration, if a little delayed. Having to remove the soil and/or rocks to replace the fabric is a time-consuming and therefore expensive process, which is also best avoided.
There are many natural alternatives that can serve the purpose of landscape fabric:
For weed prevention...
Organic mulch - Pine straw, wood chips, compost, saw dust, grass clippings
Builder's paper or cardboard - If existing weeds are a big problem, and you need to block out the sun, use one of these! Save your boxes and remove any tape or adhesives.
For erosion prevention and/or stabilization...
Coir (coconut fiber)
Riprap - Rough, loose stone 6-8 inches wide
Timber/stone baffles or terraces - Baffles are obstructions which slow or divert storm runoff and are buried perpendicular to the direction of the slope; terraces are composed of retaining walls which separate terraced levels.
Steel screen mesh - For layer division between drainage rocks and soil in container gardens (see below).
There are some cases where a geotextile may be necessary to prevent settling of landscaping rocks / stones, such as for high-traffic areas, or to more permanently prevent plant growth, such as in pathways between rows of crops. Geotextiles are thicker, stronger, and more durable than landscape fabric. However, they are still made of plastics and should similarly be avoided if possible.
Collecting Microplastics in Gardens: Case Study (i) of Soil (journal article)
Polluting microplastics harm both animals and ecosystems (article, with journal article references)
Earthworm Activity Increases Soil Health (NRCS article)
Review and Evaluation of Root Respiration and of Natural and Agricultural Processes of Soil Aeration (journal article)
Carbon dioxide and oxygen exchange at the soil-atmosphere boundary as affected by various mulch materials (journal article)