This isn’t the first time I’ve ranted about bad mulch choices and it certainly won’t be the last. But this pictorial cautionary tale is too important to pass up.
We already know that sheet mulches can be death to microbes, plant roots and animals living in the soil underneath. Our newly published research shows that landscape fabric reduces carbon dioxide movement between the soil and atmosphere about 1,000 times more than wood chip mulches do: plastic mulches are even worse. Oxygen movement will be likewise affected. And while gaps and holes in these barriers can lessen the impact, the question remains: why would you use ANY mulch that reduces gas movement? 
Yet people persist in using fabrics and plastics, usually to “smother” weeds (and that verb should set off alarm bells for anyone thinking about collateral damage to soil life). But weeds are weeds for a reason, and they will eventually colonize the surface of sheet mulches as soil, organic matter, and water collect over time.
So without further ado, here is a case study of what happens when sheet mulch is used for landscape weed control.
These irrigated landscape beds are in Wenatchee, Washington, which has hot, dry summers. As you can see, bark mulch has been used to hide the shame of sheet mulching. And from a distance it looks…okay.
Upon closer inspection, you can see the shroud of death emerging from the bark mulch (which has no means of staying in place, especially on a slope).
And even close you can see the soil that’s blown in, along with the bark and other organic matter. Just add water, and you get weeds!
Weeds, weeds, weeds! Lots of weeds. Sunny weeds!
And shady weeds!
Border weeds!
Rocky weeds!
The weeds are thriving – but the trees are not. The crowns are dying…
…and the trunks are suckering.
But you’ll note that the trees in the first photo outside of the beds are thriving.
And it’s all because of that “weed control fabric.” Which is working so well that this landscape had to be treated with herbicide the day I was there – to control the weeds.
We use the fabric under rocks only areas. You are right that is doesn’t control weeds or grass in the flower beds.
Not to be pedantic, but “suckering” is a trigger for me. I agree these sprouts are indicators of tree stress, but they aren’t “sucking” anything more than other branches do.
Branches don’t sucker – they have watersprouts. Suckers arise from the roots. These are definitely from below ground.
I think this is more of a casual definition than a scientific one, but I’ll accept it. In that case, aren’t the roots suckering (not the trunk, as stated in the caption)?
To be honest I don’t know since I didn’t rip the whole thing apart as I was sorely tempted to do. In any case, it’s a water stress response.
whoa – it looks like they *wrapped* the tree flare with plastic! Landscape fabric comes up over and over when customers complain about tree/shrub decline. I’ve learned to ask “how did you prepare the bed,” and sometimes uncover this step. “How else am I going to keep down the weeds?” is how they respond. Nobody wants to *tend* their gardens, they just want to have them done – I show them around the nursery – we weed ALL the time by hand and hula-hoe! Otherwise “pave paradise and put up a parking lot!”
As I recall, the practice of ‘mulching’ with plastic began in the 1970s. When we moved into our current garden 14 years ago, I discovered that an enormous area had been landscaped in the mid-1970s with heavy black plastic topped with about 12 inches of soil, then another layer of black plastic (into which shrubs were planted) and then topped with 4 inches of river rock. It probably looked good at first but the plants obviously suffered over the years.
Leaves and other debris filled in spaces between the rocks and eventually the shrubs’ roots began to grow into the rocks. What a mess! It took me 3 years to remove most of it but I couldn’t get it all. Several of the sickly rhodos died in the process.
That landscaping philosophy is still alive and thriving today. Too often I hear friends and relatives talk about their landscaping plans which they assume includes the need to put down landscape fabric.
How did you remove the fabric which is covered by layers of soil and “stuff”? We just moved last year and all the foundation plants around the house are planted in landscape fabric. I would like to remove it so I can plant new plants. I can’t even get a pointed shovel or knife through it! Been there for years. Thank you for your help.
You will have to dig everything out. Use scissors to cut the fabric away from the plants and remove it piece by piece. When you’ve removed a section, cover the area with a wood chip mulch and water well to protect the soil and roots. It’s a slog but if you are careful you can do this.
Because I have artillery fungus, I use flexible screening under pebble mulch at the house perimeter to prevent the stones from sinking into the soil and, of course, pull the weeds as they pop up; otherwise it’s wood chips throughout the landscape.
A reputable landscape architect and instructor told me “Nothing is wrong with landscape fabric as long as it is made of coir (coconut fiber) [because it] is biodegradable.” Do you agree?
Landscape fabric, as understood by most people, is densely woven fabric. That’s what you see in stores. Coir cloth is sold as such. It does not keep out weeds but serves to keep mulch in place. It is loosely woven so it does not block water, air or light for that matter. Its function is entirely different from landscape fabric and the names need to be kept distinct to reflect that.