Posted on | March 27, 2017 | 4 Comments
IF GARDENING know-how is the product of observation over time, then a guideline long overdue for orthodoxy is: Weed cloth always fails. Not sometimes, not most times, but always. Look for the evidence and you start seeing its black lumps protruding like coattails from shallow graves in parkways and tree wells across the country.
This is not about the practice of solarizing, which is a method of killing weeds by overlaying them with plastic sheeting until they cook to death, though there are far more wholesome ways to kill weeds or an unwanted lawn (see sheet mulching). No, this is about a porous synthetic textile also known as “landscape fabric” that has been designed to allow water to penetrate but not air or light, thus depriving weed seeds of two of three essentials for germination.
The first rub for those of us suckered into using weed cloth, or even required to do it by rebate guidelines, is that one of the very few things that weed cloth is good for is growing weeds. After a gardener covers open soil between shrubs and perennials with weed cloth and mulch, fugitive dust settling in the gravel or bark chips soon creates what amounts to potting mix. Within a year, certainly within two, this mix will be brimming with ryegrass, burclover or whatever local weed whose seeds were blown into into it. This, believe it or not, is one of the better outcomes. The photo above, taken during a trip to Los Angeles in November 2016 in advance of record rains, would have lost most of the chips to the street in the first good downpour. The upshot? A most excellent drought-resistant tripping hazard.
Meanwhile, below the weed cloth, earthworms and other organisms will have been barred from working their magic aerating and enriching soil. That’s as long as the fabric remains intact, which won’t be long. If you’ve made enough gardens, you’ll be familiar with how it becomes ripped and soon becomes not a barrier but simply a persistent and pervasive soil pollutant.
Given a propensity for failure, how did weed cloth become so widely prescribed? I’d have harsher words for this San Francisco Chronicle article extolling it were I not ashamed to be among those who have recommended it. I once accepted and repeated a landscape contractor’s insistence that weed cloth should be used beneath decomposed granite paths. Upon reflection, it occurs to me that while the contractor whose protocol I repeated had laid thousands of paths, he quite possibly had never weeded one. The beauty of DG surely is that you may pluck a weed, tamp down the DG down and have a path that’s good as new. Moreover, a more typical place for weeds to appear along DG paths is the earthen bank where they enjoy drainage. There’s a beautiful answer to this called wildflower seeds.
It’s even more tempting to use weed cloth underneath a path made of pavers because weeding the intersections is both tedious and hard on the knees. So, is weed cloth preferable to the more toxic pathway treatments such as RoundUp? That’s only a choice if you believe that weed control boils down to options ranging between bad and worse. There remain three far more wholesome, time-honored approaches to weeds: A) Pull them. B) Put up with them. C) A combination of A and B.