By Kathleen Cue, UNL Extension Horticulture Educator
Whether you use landscape fabric beneath mulch in outdoor spaces depends on what you know about it. The two main reasons landscape fabric is used are A) a desire to keep weeds down and B) employing any means necessary to keep rock mulches from sinking into the soil after a rain. Unfortunately, neither of these reasons assures landscape fabric will function as planned.
Here is why.
Landscape fabric is a temporary weed barrier, suppressing weeds for a few years. Ultimately soil and seeds blow in, settling over the fabric and creating the perfect environment for seed germination. Emerging weed seedlings send roots through perforations in the landscape fabric, growing their merry way downward. When these weeds are pulled, roots pushing through the landscape fabric will cling to the fabric as well. Then weed removal entails disentangling roots from the landscape fabric, which has been pulled up too. Once weed development becomes an issue, weed problems are ongoing because of continuing accumulation of soil and weed seeds above the fabric.
The second reason not to use landscape fabric, and a more compelling one, has to do with creating a healthy growing environment for desired plants to thrive. All plant roots respire as part of their natural growth and development, taking in oxygen and giving off carbon dioxide. This exchange of gases, as it is called, is interrupted by the presence of landscape fabric and rock mulch. The results are less plant vigor, more plant stress, and less natural defenses to ward off insect and disease problems. If you have ever removed landscape fabric, it was likely the soil beneath was slimy, a sure indication of a poor growing environment for plant roots.
Are there instances where landscape fabric has an application? Yes. In windswept environments, landscape fabric and rock mulch may be the only thing protecting plant roots. Master Gardener Lynn had just such a situation, with the wind rounding the corner of his house with the fury of a wind tunnel. Everything planted near this corner died, with wood chips and soil blowing away, exposing plant roots. He found landscape fabric and rock mulch were the only things immune to the wind and protective of plant roots. Lynn eventually converted the space over from landscape fabric and rock mulch to solely wood chips, once a nearby windbreak grew enough to provide protection.
When planning your landscaping projects, consider landscape fabric as one expense to do without. Not only will this save you some money and effort, but your plants will thank you with increased health too.
Go to Dodge County Horticulture Web Page for more gardening information.
Photo Below: Landscape Fabric