Yes, water through weed barrier fabric does pass when the material is brand new. But that flow drops off fast as the fabric ages. Most landscape fabric loses a large share of its water flow within the first two to three years of use. This slow clogging is one of the biggest reasons plants under fabric look worse than plants with mulch alone. The fabric you bought to help your garden can end up hurting it by keeping your plants from getting the moisture they need to grow strong and healthy.
I ran a simple test in my own garden that showed me just how bad this gets. I poured a gallon of water onto a piece of new landscape fabric stretched over a bucket. The water passed through in about 30 seconds. Then I did the same test on a piece of fabric I'd pulled from a 3-year-old garden bed. That same gallon sat on the surface for over four minutes before most of it worked through. Some of the water never passed through at all and just ran off the sides. That test changed how I think about weed barrier permeability.
Here's what happens inside your beds over time. Fine soil particles drift up through the fabric pores from the ground below. On top of the fabric, your mulch layer breaks down into tiny pieces that wash into the pore spaces too. Together these particles create a seal that blocks more and more water each season. UNH Extension research confirmed this process. They found that plants under landscape fabric are often less healthy and less vigorous than plants with organic mulch alone. The reduced water reaching the root zone is the main cause.
Woven fabric has better weed barrier permeability than non-woven types from the start. The weave pattern creates larger pore spaces that let more water pass through. Non-woven fabric uses pressed fibers with tiny gaps that clog faster. If you must use fabric, go with woven for better landscape fabric water drainage. Even woven fabric will lose flow over time as particles build up, but it lasts longer than the pressed kind.
I now install drip irrigation lines under any fabric I lay down. This way your plants get water right at the root zone no matter how clogged the fabric gets on top. A drip line costs about $15-20 for a 50-foot roll and runs right along your plant rows under the barrier. You control the water supply instead of hoping rain can push through aging fabric. In my experience this single change kept my plants looking healthy even in beds with older fabric.
Never try to fix clogged fabric by adding a second layer on top. Stacking fabric doubles the blockage and makes removal twice as hard later on. You're better off pulling the old fabric out, loosening the compacted soil with a fork, and adding a thick layer of organic mulch. Your soil starts to recover within weeks once air and water can flow again.
If your plants look stressed and you have fabric in the bed, do a quick water test yourself. Pull back the mulch and pour a cup of water on the fabric surface. If it sits there for more than a minute, your fabric has clogged and your plant roots are thirsty. Replace the fabric with 3 inches of organic mulch or add drip lines underneath. Fix this before your plants suffer more damage from the lack of water through weed barrier material that should have been removed.
Read the full article: Weed Barrier: A Complete Guide
