Weeds & The Evils of Landscape Fabric
Updated: Jan 9, 2021
I have mentioned a few times how much I dislike landscape fabric and I thought it was time I explained myself. I will apologize in advance, as this might get a little ranty. It just makes me miserable to see people waste their time and money in the garden. So please indulge me a little as I get this off my chest. Here goes.
Landscape fabric is most often used as barrier material under a layer of rock or mulch. Sometimes it is laid underneath paving stones. It is supposed to prevent weeds from growing up from underneath the fabric. Along with the rock, it is touted as the ultimate in a maintenance free yard. You will never again need to do any work whatsoever.
Unfortunately, that's not how it works in real life. This is what actually happens:
It looks great for a year or two. During that time, the wind blows small particles of dust and dirt into your rocks. Maybe some leaves or other small pieces of organic material get blown in as well. Maybe the neighbourhood rabbit decides it's a great place to leave a few brown pellets too. All this material sinks down between the rocks and settles on top of your landscape fabric. Using a leaf blower may get rid of some of this, but it will never get rid of it all. That organic material just keeps building up.
The other thing that blows in is weed seeds. Lots and lots of weed seeds. Most of the weeds that grow in our yard are from seeds that are blown in, not ones from deep down in the soil. (Unless you turn over your soil and bring those seeds to the surface. Which is why the no-till method of gardening is something I am a big supporter of.) So, you now have weed seeds that have found the perfect home on nutrient rich, well-drained soil that is now built up enough to be exposed to the sun.
And those seeds will sprout. You may wonder what the big deal is. If we had bare soil the same thing would happen right? Yes, it would. The problem is that the roots of those weeds now grow into, and get tangled up in, that landscape fabric. When we pull weeds that are growing in bare soil we can get the whole root out. If it is a weed growing in mulch it is even easier to pull and get the whole root. When we pull a weed that has its roots entwined in landscape fabric we leave a good chunk of those roots behind. They are physically impossible to get all of. So even when we pull it, that weed is not only still there, it has an already established root system allowing it to come back stronger than ever.
I did say weed seeds underneath the ground are nothing to worry about, and that is true, but tree roots are another story. If you have any trees or shrubs nearby that like to sucker (aspen, chokecherry, lilac are just a few of the many), those roots will flourish underneath landscape fabric. And they will continue to run until they work their way up through any tiny tear or weak spot. It doesn't matter how industrial strength your fabric is, nature will eventually find a way. And once it starts to sprout, it is impossible to get rid of. The way you usually remove suckers is to simply dig from the shoot all along the root as far back to the main tree as you can. Under landscape fabric, you need to move the rock and pull up the fabric along the entire root line, pull up the roots, then replace fabric and the rocks again. And then fix the hole in the fabric. The pictures below illustrate an aspen sucker under heavy duty landscape fabric and gravel and just the start of the roots underneath. That's a lot of roots!
A quick note about herbicides, which I have often seen used to control weeds in rocky areas like we are describing. Keep in mind that insects and other microorganisms live here too. Some of these are beneficial to us and some are food for birds and other animals in our neighbourhoods. Not only that, spraying with herbicide will only temporarily stop the weed growth. It will only kill what is actively growing and will add even more organic matter to your soil topped fabric with the dead weeds themselves. Then you must reapply it, again and again. Herbicides will also be absorbed by any tree suckers or roots growing under your fabric and travel through those roots back to the tree they originated from, poisoning and potentially killing it.
You may be a very attentive gardener that consistently picks weeds out of their rocks, but leftover weed roots and tree suckers will eventually degrade the fabric until you are left with a weedy mess that is impossible to control and shredded landscape fabric underneath that no longer functions in any way. The only option is to rip it all up and start again. Not so low maintenance is it?
So what is the alternative? How do we keep the weeds under control? How do we have a low maintenance yard? There is an easier way (and cheaper too!).
Let me get two things out of the way before we continue:
There is no such thing as a maintenance free yard. Lower maintenance, yes. Maintenance free, no. Even an entire yard of poured concrete will eventually end up with cracks and weeds that will happily grow in those cracks.
Weeds are going to happen. They will find a way. Every single garden in the world has weeds. There are steps you can take to greatly reduce a weed's ability to germinate and grow, but you will need to remove young weeds early and often. Yes, every single gardener weeds.
Sorry, but it's true.
Like in many sports, the best offense is a good defense. So let's begin with some methods to discourage weed growth in our space:
To start with, don't till your soil. Tilling brings weed seeds to the surface where they are exposed to all the things that make them grow: sunlight, moisture and oxygen. And trust me, there are tons of weed seeds down there. This goes for your annual vegetable beds as well as mixed flower beds.
Make sure your existing plants are healthy. Ensuring your soil is full of nutrients and organic matter (hint: add good quality compost every year) will result in big healthy plants that can easily out-compete weeds. This is doubly true for lawns.
Ensure your garden beds don't have big empty spaces. Weeds can't grow where there isn't any available space for them. Dense planting where sunlight cannot reach the soil between plants will result in less weed seed germination. Dense planting above ground also means dense roots below ground, and less room for weed roots to get established. If there is room, mother nature will find a way to grow something. So make sure it is something you actually want to be there.
All that is great for our garden beds, but what about all those areas that don't really grow anything well? What about the dead spots that are the usual targets for fabric and rock? I'm looking at you, shady narrow side yard! There are some areas out there that are really challenging to grow in, but it is always less work in the long run (and better for the environment) to work with nature, rather than try and suppress it. You are going to need to do a little research into what you can grow in your particular area. Go to your local garden center and talk to the people in perennials and trees and shrubs. Tell them about your space and its challenges. There is almost always something that will work. For example, Snow-on-the-Mountain (Goutweed or Aegopodium podagraria) is a tough, resilient groundcover that can handle zero sunlight and very poor soils. It works fabulously in areas where nothing else grows. There are also a number of ground covers that work in sunny areas, or that are shorter and better able to be walked on if you have a high traffic area. See the pictures below for just a few of the many options for ground covers. Chances are there is something that will grow well and out-compete your weeds. And it will look beautiful, create oxygen for you, improve your soil and be a home and food for wildlife. One more way to help save the bees. That's a lot more than rocks and fabric will do for you!
From left to right: Creeping thyme, Scotch moss, Speedwell (Veronica), Creeping Jenny, Moss phlox.
By far, the most effective way to prevent weeds from growing is to use mulch. A good thick layer of it. Straight over your soil, no fabric in sight. This works for those areas in your flower beds between plants and it also works for those large swaths where you don't want any growth at all (although, I still think you should try growing something!). Any weed seeds landing on top of the mulch don't germinate because they are not in contact with soil, and those that do work their way down to the soil level have no sunlight for germination. You need a good 2-4" of mulch for this to work well. And you will need to top up this mulch every 4-5 years to ensure it stays at 2-4" deep. This is not a miracle cure. You will occasionally have a few weeds that germinate. But, you are going to be attentive and get them when they are young and small and super easy to pull out (along with their entire root), right?
If you don't stay on top of things, you end up with beds that look like the one above. Many garden beds in city parks look just like this. This is what happens when you don't use deep enough mulch, don't pull weeds when they are small and manageable, and don't top up your mulch. I must give the city credit though, at least they don't use landscape fabric underneath. Mulch can be beautiful in and of itself, but it also benefits your garden in a number of ways, besides just weed suppression:
Breaks down and adds organic matter and nutrients to soil.
Promotes beneficial fungal ecosystems.
Prevents water evaporation, so you need to water less.
Buffers the soil temperature keeping it cooler in the hot summer months and warmer in the winter.
Prevents erosion of soil due to water runoff and wind.
Suppresses diseases by preventing soil (and soil borne diseases within it) from splashing up onto plants during rain or watering.
Insulates plant roots in winter so they have a better chance of survival. This is especially important here in Calgary where we don't have much winter snow cover to insulate.
Please make sure that, whatever mulch you do use, it is plant based. That means no plastic (that's a hard no) and no rock. Bark, shredded leaves, straw (not hay, that has seeds), chipped wood and pine needles are all great things to use. Anything that will break down and add to the organic matter nutrients in your soil will be fine. Try to stay away from dyed mulch if you can. The dye is vegetable based, but the wood used tends to be suspect. It is often from pallets that may have been treated with chemicals. There is a lot more information to talk about regarding mulch. Look for an article coming out soon that will go into everything mulch in detail.
If you are still having problems with weeds, it helps to know why. Figuring out exactly which weeds are growing in your yard and why they are growing is a good start to preventing them from growing in the first place. Have you ever noticed that it is weeds that grow in abandoned lots or on really poor soils? You never find a rose bush growing lushly on an old construction site. That's because weeds usually grow in soil that is compromised in some way. They are opportunistic growers. Dandelions are a perfect example. They grow in very hard, dense soils. They have a long tap root that is fantastic for breaking up those compacted soils. (They actually help to improve poor soils over time, as most weeds do, by the way.) So one solution to a dandelion problem is to decompact your soil. Yarrow (the weed, not the ornamental perennial) grows in very low fertility soils (especially those low in potassium) that are sandy and dry. You can figure out how to resolve that, right? Compost will add organic matter to help with the sandiness and the dryness, as well as increase the soil fertility.
Think about having your soil tested if you have any concerns about severe nutrient deficiencies or toxins. Use the results to improve your soil. Again, ask at your garden center for recommendations to address specific nutrient deficiencies. Healthier soil will help wanted plants to grow and discourage weeds that prefer less ideal conditions. If the results point to toxins or heavy metals, consider contained raised beds with new soil. And do some research into plants that bioaccumulate toxins. There are many plants used in remediation that take up specific toxins and heavy metals so they can be safely removed and disposed of. It is always better to improve your land rather than cover up and ignore any major issues. By the way, that is one of the major principles of permaculture. Our aim is to be more than sustainable, it is to be regenerative.
We talked a lot about weeds and how much we really don't want them in our yards in this article, but I also want you to think a little about the good side of weeds. Dandelions are often the first food available to our bees in the spring. Chickweed not only tastes fantastic in your salad, it is a nutritional powerhouse too. There are quite a few edible weeds, actually. Plantain, mullein, yarrow, nettle and wormwood are all weeds that are widely used in natural medicine. So pause just a moment before you pull that weed and identify it. Would it be okay if it hung out in your garden for just a while? Maybe just until it was done flowering and before it set seed? Or maybe just until it grew to its full yumminess so you could harvest and eat it? Just saying, pulling may not always be your only option.
So now that I have smack talked it for an entire article, is there ever a time or place for landscape fabric? Actually yes, there is. It belongs in a place that is not going to get anything blown onto it (seeds or soil) and that will not be exposed to sunlight. The only place that qualifies is under your completely sealed off deck. That's it. Sorry landscape fabric industry.
AGAT Laboratories (https://www.agatlabs.com/agri-foods/agricultural-analysis/soil-profiling.cfm) for soil testing in Calgary
What Weeds Tell You About Your Soil (https://www.almanac.com/news/gardening/gardening-advice/weeds-indicator-plants#) by The Farmer's Almanac
Weeds as Soil Indicators (https://www.motherearthnews.com/organic-gardening/soil-indicators-zmaz87jazgoe) by Mother Earth News
M. Cristina Negri, Ray R. Hinchman, Plants That Remove Contaminants From the Environment,Laboratory Medicine, Volume 27, Issue 1, 1 January 1996, Pages 36–40,(https://doi.org/10.1093/labmed/27.1.36)
5 Best Plants for Bioremediation (https://land8.com/5-best-plants-for-phytoremediation/) from Lanscape Architects Network