Problem
The sad fact is, when xeriscaping, nothing can stop the weeds. Even if you clear the weeds completely, install weed barrier, and lay 2”+ of gravel, there is a possibility for them to come back. Nut Sedge roots and Bermuda rhizomes can run as deep as 22”, and they can sprout back as soon as the first rain after “removal.” Weed barrier does delay weeds, but it also makes it more difficult to remove the weeds once they come back due to the root being under the barrier. Not only that, exposed weed barrier is most definitely an eye sore. What can you do? Should you install weed barrier or not?
Proper Preparation
While the issues mentioned above still remain, the best way to being xeriscaping is by preparing the areas properly. All weeds must be removed by the roots 2-3” beneath the surface of the ground. Some people choose to use pre-emergent herbicides, which can delay the amount of time it takes for weeds to emerge. Tillers end up turning too many weeds back into the ground. We like to use a sod cutter to do all of our prep work. Taking the time to properly remove all the weeds is the first and best defense against “xeriscapes gone wild.”
Material Selection
Different landscape materials affect the growth of weeds in a variety of ways. Some materials can promote weed growth while others tend to inhibit it. For example, decomposed granite seeds to be a perfect conduit for Broadleaf Spurge. Further, seeds can sprout and grow in decomposed granite in the absence of soil. The larger the landscape material, the harder it is for weeds to thrive. An inch and a half river rock will stifle weed growth better than a smaller gravel. Material volume is also an important factor. When installing landscape material it is best to lay the material 2”+ in thickness. Hardwood mulch is best installed at a 3-4” thickness. However, we do not recommend using weed barrier under mulch. The more material, the better— cost is the only prohibitive aspect with regards to volume of material used. The thicker the material laid, the less need for weed barrier there is.
Sun and Water
Most plants require two important things to grow: sun and water. Weeds are not excluded from this. When installing any xeriscape beds, note that there will be more weeds in sunny and/or irrigated areas. It will be especially difficult to deal with the weeds in these areas, as this is where they will thrive. To help manage the watering aspect of things, we recommend a directed type of irrigation such as drip irrigation or bubblers.
All Things Considered…
Using this information, you can make the decision for yourself. Here at Terra Dura, we will continue to use weed barrier to slow the weeds down in the sunny areas and use discretion in shaded areas. When (not if) you get weeds in your xeriscaped beds, it will be much harder to remove weeds in their entirety if weed barrier is installed. Maybe 20-30 years down the road there will be an amazing new innovation in landscaping that takes care of the weeds, until then we will continue to use weed barrier. We hope this helps in your next xeriscape project.