[Grant]

OK, what do y'all think about laying landscpe fabric under mulch to prevent weed growth? I get asked this question frequently and logically it makes some sense. However, practically I find that the fabric does little if any good in preventing weed growth as most of the weeds germinate in the mulch that's above the fabric. Additionally, if you ever have to go back to plant anything else, you have to deal with the fabric. What do you think?

[stoneridge]

Its pointless to put a weed barrier fabric under mulch. Your better off using a pre-emergent, or getting down on your hands and knees and picking the few that germinate in the mulch.

[Pelican]

Don't bother with it for weed control. It's a myth that weeds sprout from the soil, they grow from the top down whether the fabric is there or not.

The fabric can be used to keep your mulch from being absorbed by soft, moist soils. This is especially true when using stone mulch. Other than that, you're wasting your money.

[GLAN]

Ditto........

[4seasons]

I think it actually magnifies your weed problem.
fabric is just about a pain in the hind end when doing anything in the flowerbeds.

[johnkeegan]

I'll present the other opinion... First off don't use the cheap stuff. DeWitt Pro 5 is good. Keep the mulch at around 3" (more is not better). And don't blow lawn clipping (i.e. weed seeds) into the bed.
Nothing is 100% effective. Certain weeds germinate in mulch. Does that mean we don't mulch because it's not 100% effective? Of course not . Mulch HINDERS most weeds. Just as weed mat HINDERS many weeds and suckers and invasive plants, especially those that move underground.
It also slows the decompositon of the mulch by 30-50% because it creates a barrier between the mulch and organisms in the soil that break it down.
Plus, on many larger jobs we can do our planting and lay the mat right over the sod and then mulch. No need to remove the grass.
So, will it stop future weeds that can germinate in anything from mulch to stone dust ... no. But will it will it stop many of the initial weeds and invasive underground runners and slow the breakdown of the mulch...yes. Are either or both used together 100% effective... no.

[TrickyDick]

Whether landscape fabric helps prevent weeds for a year or two seems pretty irrelevant to me when you consider the inevitable disaster that will appear after a year or two of freezing and thawing soil (in places where that is an issue). Black stuff sticking out through the mulch all over the yard and absolutely no good way to fix it once it starts starts to show. Either cut out the exposed stuff or fultily pile on more mulch. Just my opinion but I will never use the stuff except somethimes under stone. And I don't know for sure about this but the smartest plant guy I've ever known told me that if a fabric is thick enough to prevent things growing up through it it is also thick enough to inhibit plant respiration, etc. and can be harmful to the landscape plants.

[4seasons]

tricky
you typed word for word exactly what I wanted to say!
As for the last part, I've seen shingles,plastic,and cardboard; all used under the mulch or on top. They didnt seem to phase the plants. The plants that were thriving in these conditions seemed bothered more from the animals or constant butchering.


Bruce

[johnkeegan]

I'm surprised you wrote about plant respiration. I thought it was common knowledge that landscape fabric is porous to air and water. Hold it up to light and you can see tiny pinholes of light passing through. These tiny holes allow plenty of air and water to pass through but are small enough to hinder most (not all) weed runners and suckers.
Again, I thought this was common knowledge so I'm surprised your "expert" was unaware of this.
I do wonder sometimes if many landscapers are turned off by landscape fabric because they've only used the cheap stuff. Products like the DeWitt Pro 5 I mentioned are MUCH more expensive than the 2 and 3 oz. weight products. But guess what? You get what you pay for. Many of my customers ask to buy some off me for themselves because it's simply not sold anywhere. Even my local wholesale nursery stop stocking it because they say most guys want the cheaper stuff.
By the way "freezing and thawing" of the soil do not cause the fabric to pop up. It simply wasn't installed properly. For instance, some guys leave large folds or flaps when they lay it and it surfaces after a few heavy rains. Or they lay it over stumps, rocks etc. Or they extend the mat too close to the bed edge and the mowing guy snags it.

[TrickyDick]

John I think the point was that those same little holes allow some of the more industrious weeds to grow through the fabric, unless you are putting down gortex, and that anything with a tight enough weave to prevent that is going to prevent more than just weeds from getting through. This is a general statement that is obviously less true of some products than others. Most weed fabric does not hurt plants but also does not do much to stop weeds from growing. The stuff you use probably works a lot better than what most people use but it still only works for a short time until the mulch starts to break down. Then you've got soil forming ON TOP of your fabric with plenty of weed seeds in it and plenty of airborn weeds to grow in your mulch. Yeah it may take a couple of extra years but your going to end up with the same stand of weeds or brush or whatever if it isn't maintained well and the fact is that most clients who are interested in having fabric put down want it because they don't want to have to maintain it well. The only difference over time is that one weedy yard will have landscape fabric six or eight inches under the soil and mulch while the other will not which will make it easier to clean up the mess. The fabric is a short term solution to a long term problem that can only really be dealt with through good maintenance practices.

As for freeze/ thaw...I disagree. Freezing causes the soil surface to heave unevenly, creating high spots and low spots over time. Mulch, soil or whatever will creep off the high spots and settle into the low spots. It happens slow but eventually you've got exposed fabric everywhere. And yeah you can keep piling mulch on it but because it is breaking down slower that's not a very good idea either.

I agree that there are rare occasions where putting the stuff down makes sense, like trying to choke out a buch of nasty invasive stuff that was just cut, and I agree that using the best products and installing them well will maximize how long and how well it works but I still think that at least nine out of ten times weed fabric is an unnecessary expense and a long term liability.

As for the common knowledge...you would think it would be but I don't think all the people I see spreading black plastic sheeting in landscape beds got the memo. I'm pretty sure though that my expert (I didn't say he was one...but he is) knows that that is not usually a good idea since it is not permeable like landscape fabric.

I haven't been in this business for too long and I could be wrong. There are many things that I don't know enough about but until someone shows me a landscape with a fabric weed barrier that is more than five years old where I don't SEE the fabric I'm sticking to my guns on this one.

[johnkeegan]

I agree that "good maintenance practices" are the real culprit with weed growth. For instance, if there are 6-8" of mulch on a bed, as you stated, there's going to be problems. Landscapers need to educate the customers on the fact that too much mulch is bad for plants. Of course, part of the problem is that some guys are really in the business of selling mulch and not interested in plant health.
Over the last 15 years since I've gotton heavy into design/planting, I've literally installed acres of landscape fabric and I still do work on many of those properties. Seeing fabric is extremely rare. Even in those cases, it's because one of my guys didn't follow the "weedmat-laying-guidelines" I mentioned above. If freeze-thaw was the culprit I'd see it everywhere I've worked.
Believe me, our job would be MUCH easier if we didn't have to install weedmat. It's a pain. And I know it's an added expense that I know many of my competitors like to skimp on. But I really believe that one of the things that will get return business from a customer that just did a plant install with us is that the beds are low maintenance. If there are alot of weeds the first year or two, they won't do any more planting. Therefore you've lost your most important asset...a happy, return customer. If the beds stay low maintenance over those two years,however, they have the confidence to move ahead with more planting projects... And you've got priceless referral.... And many of those return customers say, "...you're going to put that fabric in there again, right..."

[Nebraska]

Isn't it pointless to install a weed barrier fabric under mulch since after a few years when the mulch breaks down you will essentially have soil under the fabric and soil above the fabric?

[P-Train]

For the most part, weed fabric is a homeowner/big box store marriage that is like a functioning alcoholic.

[TrickyDick]

I guess from a marketing perspective you may have a point. A year or two of reduced maintenance will no doubt leave a client feeling like you did something magical to thier yard. One could also make the argument that it will leave that client with an unrealistic expectation of what maintenance is really necessary for thier yard and that they will be in for a nasty surprise when they or thier maintenance contractor starts spending extra hours each week on a trimmer or slinging a sprayer of round-up. It has obviously worked well for you John but for me that year or two of reduced maintenance and whatever marketing value that has are far outweighed by the long term liability of placing a layer of non-biodegradable stuff that will be in the landscape forever (or until someone performs the huge PITA job of removing it) that will only be effective for a few years. And I have to admit that irrespective of how effective it is it just kind of leaves a bad taste in my mouth to install something so permanant and unnatural when I am trying to create a little piece of nature in an otherwise manufactured environment.

Now if someone made an effective weed barrier that broke down after 3 or 4 years...I'd be all over that.

[johnkeegan]

I've noticed a misnomer that keeps getting repeated here. If mulch is not in contact with soil (because of weedmat) it does not turn into "soil" unless soil is added to it. Mulch is straight organic matter. Soil is "10-20% organic matter (decayed plant life, such as mulch), 80-90% mineral matter (rocks, sand, silt, clay)," as quoted from the "Victory Garden Landscape Guide," Thomas Wirth. (The only handy book I had with a "soil" definition).
Now if soil gets mixied in with the mulch from planting, bed edgings etc. I guess it then can be classified as soil.
This is why (near) 100% organic matter such as "mulch" is effective at retarding most (not all) weed growth and germination. Leave a pile of straight mulch and a separate pile of true soil in an open area and see which grows weeds first.
But once you allow the mulch to come in contact with the existing soil you create a richer soil than you originally had, which the weeds love once they can sink their roots into it. The landscape fabric creates a barrier between the true soil and the organic matter (mulch). Thus not only slowing the decomposition of the mulch but also preventing the creation of that super rich layer of soil under the mulch, which is like a shot of steroids for the weeds..... And, no it's not good for the plants you installed to have that super rich soil at the top. Encouraging roots to grow up is not a good idea long term.
...sorry for the boring soil structure ramblings.
..and Tricky,you say, "it just kind of leaves a bad taste in my mouth to install something so permanant and unnatural," I don't about you but I install alot of pavers and segmented retaining walls (with geogrid). They're quite "unnatural" and I hope they're around for a long time but it reallys doesn't create a moral dilemma. And which is more damaging to the environment, landscape fabric or weedkiller, which you may not personally use but along with pre-emergents seems to be the preferred way to combat weeds.