The lone voice of horticultural reason

“Using weed barrier fabric means you won’t have weeds.”

Nothing could be farther from the truth. Few products foisted on homeowners by landscapers and the gardening industry are as worthless as weed barrier fabric.

In the photo you see a shrub bed (that’s a Rhododendron upper right) we renovated this summer that had weed fabric spread atop ever inch of soil by the previous landscaper, except where circles had been cut to plant the shrubs. I use this photo because the landscaper, after laying the fabric, cutting all the circles, and planting all the shrubs, mulched the bed (and every other bed on the property) with three inches of gravel mulch. If you’re not from the Midwest, well, gravel as mulch in garden beds is a wholly unexplainable phenomenon.

Everything that’s green in the photo, except for the rhodie leaves, is a weed. A year or two after mulching, organic material has filtered down into the gravel (from spent flowers, leaves that aren’t completely removed in fall, microscopic soil particles carried by wind and rain) and when weed seeds hit (often airborne), they germinate and grow just fine.

If weeds will grow in rock mulch atop weed barrier fabric, what is the weed barrier fabric doing there? Annual weeds germinate just swell in shredded wood mulch, of course, so again, the weed barrier fabric beneath the mulch is doing what—beyond not allowing an organic mulch to slowly decay and rejuvenate the soil?  Oh, it’s blocking the light and killing all the perennial weeds in the soil. Yeah right, tell that to anyone who has ever combated Canadian thistle (Cirsium arvense). Most perennial weeds blast right through plastic week barrier fabric, and however many inches of mulch.

Weed fabric is superfluous. Mulch, preferably organic, in a three- to five-inch layer, blocks out all the sunlight and keeps weed seeds in the soil from germinating. Weeds that germinate atop the mulch are inevitable, and need to be pulled by hand about once a week. Be diligent about it and by midseason the weeding of your beds takes minutes per month. Weed barrier fabric serves no purpose, except driving you crazy every time you alter or add to the planting scheme. You will eventually tear it all out, or I will.

Don Engebretson
The Renegade Gardener