I get it, weeds are a real pain. Anything we can do to save ourselves some time, and backache, is welcome. Enter: weed fabric, also known as weed barrier, landscape fabric, or underlayment. Whatever you call it, it comes with problems. Here, I’m going to list some of the disadvantages of using landscape fabric. Scroll all the way to the bottom to learn what to do if you have already laid some out, and what to do instead.
1 - Water
Though most products will claim otherwise, weed barrier fabric disrupts the movement of water from above ground to below ground, and vice versa. First, it can be hard for water to get through the fabric and down to the soil. This means your plant could be drying out, even if you are applying water around it. And second, if you happen to have slow draining soil (or have applied a lot of water in response to wilting), the weed fabric will worsen the problem. It prevents water from evaporating as quickly, which can lead to root rot, especially in plants that are sensitive to wet soil.
2 - Gas
Just like it disrupts the movement of water, it also changes the way gas can move between the soil and the air. The fabric can prevent the carbon dioxide emitted by the roots from leaving the soil as it normally would, which can lead to toxic build-up that harms or even kills the plant.
3 - Heat
Landscape fabric works a bit like a blanket, holding in heat around the plant. When the temperature under the fabric is much higher than it should be, the roots will usually just stop growing. If the temperature remains very high, they can go into a dormant state. This effect is worsened when parts of the fabric are exposed, as most weed barriers are very dark in color.
What if my garden already has weed fabric laid over it?
Rake away any mulch that’s under your plants. Peel the fabric away from the plant and cut away in an 18-24″/45-60cm radius around the base to expose the soil directly over and just outside the rootball. Replace the mulch. This will help the plants in the meantime, but the fabric should be removed eventually to ensure the long term health of your soil.
Why shouldn’t I use weed fabric in areas without plants?
It causes many other problems that affect more than just plants. It harms the soil and the microorganisms living in it through superheating and a lack of adequate oxygen and water. Worms don’t enjoy this environment, so they won’t be present as much to keep it aerated. Over time the soil can become compacted. It also prevents the soil from improving. Organic material is supposed to be able to break down directly on top of the existing soil layer, which adds nutrients below and enhances the structure.
How do I know if my weed fabric is causing problems for my plants?
Problems will show themselves in a few different ways. The most common is that your plant isn’t growing, and what growth you do have is sparse and unhealthy looking. Yellowing leaves or burnt leaf margins are also a sign of a water problem, which can be attributed to the weed fabric in this case.
What can I do instead of using a weed barrier?
– Use an organic mulch like wood chips or shredded leaves. It will help prevent the growth of many weed seeds.
– Plant a perennial ground cover. It will outcompete most weeds.
I need to use landscape fabric for my eroding slope. What do I do?
Select a natural woven barrier with large holes, like burlap. Thanks to its large holes, it won’t prevent the exchange of gas or water, but it will still stabilize the soil and prevent a washout. It will break down eventually, but your soil should be stable by then thanks to an established planting.
I want to make my small yard into a rock garden. I have been warned by friends who experienced the problem that if I don’t lay down a barrier it quickly becomes a pain to weed. Mulch breaks down (from my own experience) and using mulch just delays the weed problem a few years at the most and you don’t want to keep piling much on top of a rock garden..
Unfortunately, there isn’t an exception to using weed fabric for a rock garden. It creates poor conditions for all soils in all garden types. If fabric is laid down and each plant is given a wide hole in the fabric, it this would still create poor conditions surrounding the plants and for the organisms that are trying to keep the soil healthy. Wish I had better news, but the answer is just an unsatisfying one.