Benefits of Mulch
If your soil is clayey and poor, with little organic matter, like it is in many areas of Colorado, using weed barrier fabric underneath your wood mulch or bark is a big mistake! Mulch is beneficial in gardens here in Colorado for a number of reasons. It reduces the amount of moisture that evaporates from soil, it helps keep plant roots cool – even in really sunny spots, and it helps control weeds. It can also make gardens look more attractive and well kept! But one of the greatest benefits of using wood mulch in gardens with naturally poor soil is that it gradually improves soil quality. That benefit is hard to beat! However, to enjoy this perk, you need to avoid using weed barrier fabric under your mulch.
Too Much Lawn
When we moved into our current home, our yard had been landscaped with just a few trees, and a light sprinkling of shrubs and perennials. Mostly there was lawn – lots and lots of lawn. The lawn was green and lush and was obviously the previous owner’s pride and joy. So naturally, one of the first things I did once I moved in was tear out a good portion of that beautiful green lawn to replace it with garden beds!
Building Garden Beds
Low maintenance beds, especially in my front yard, were a priority. I carefully planned out the shapes of the beds and tore the grass out of those areas. For the front yard beds, I brought in a big load of garden soil and mixed it in with our native soil, which is awful, poor, clay with next to no organic matter. (My back yard beds didn’t get the special treatment of amended soil which was a lousy decision that I will discuss another time!) I shaped the beds to mound up into just the right shapes. And then, thinking it would make my beds lower maintenance, I installed the best quality weed barrier fabric I could find over my perfectly prepared beds. What a massive mistake!
I spent a lot of time putting down the weed barrier fabric, not to mention how much money I spent on it! I carefully cut holes out of the fabric and planted my trees, shrubs and perennials in them. Finally, I spread a layer of mulch over the fabric. I was really satisfied with the results at first. But it only took a couple of years to realize what a terrible mistake that weed barrier fabric was!
Weed Barrier Fabric is a Poor Choice for the Indecisive Gardener!
I am an indecisive gardener. More often than not, when I plant something, I will dig it up and move it within a year – or maybe even within a day! It was a real pain to cut holes in the fabric every time I planted or moved something. I ended up with loads of holes that no longer even had anything planted in them. This is definitely one good reason to avoid weed barrier fabric if you are an indecisive gardener. But it wasn’t the worst problem I had.
Don’t Separate the Good Soil from the Poor
The biggest problem with using weed barrier fabric under mulch is that the mulch breaks down and creates fabulous, rich, fertile soil that piles up on TOP of the fabric. This broken down mulch becomes better soil than almost any native soil that you will find in Colorado yards. And it will most likely be better than the soil that is underneath the fabric.
Soon, many of the plants in your garden will realize that they prefer the soil on top of the weed barrier fabric over what is below it. They will then begin to grow new roots ON TOP of the fabric! Once their roots really take off in the fertile soil above the fabric, the existing roots growing in the poorer soil beneath the fabric begin to wither away. Before you know it, they may no longer have their original roots down in the soil below and will only have roots growing along the top of the fabric. That is how I lost one of my favorite plants!
Time to desegregate
I had an absolutely gorgeous Pink Elephant Hardy Hibiscus. I planted it in a bed lined with weed barrier fabric and mulched around it. This was a bed in my backyard, and the soil that the hibiscus was planted in had barely been amended. After a few years, I realized that I had several inches of fantastically fertile soil on top of my weed barrier fabric and that it was never going to be naturally churned into the existing soil. I really wanted the benefit of eventually having better soil due to years of adding mulch to my yard, having it break down and work its way into my poor soil.
The weed barrier fabric was not reducing the amount of weeds growing in my garden; the mulch did that. If my layer of mulch got too thin, weeds would quickly pop up in the fertile soil on top of the fabric.
I was sick of cutting pieces out of the fabric every time I planted or moved anything in my garden. And the rich soil was burying the fabric deeper and deeper, making it more difficult to cut holes in. So I decided to tear out all of my weed barrier fabric.
Trying to Right a Wrong
As I started tearing the weed barrier fabric out of my bed with the Pink Elephant hibiscus, I realized there were loads of big roots growing all over on top of the fabric. I pulled them off of the fabric to preserve them and traced them back to whichever plant they belonged to. But I wasn’t overly careful about it because I assumed that the plants would still have plenty of roots growing down into the soil beneath.
Tearing out the fabric was a big task. It was spring and I had a lot of work to do in my garden! So I just tore through the job so that I could move on to the next project. A rather large number of the roots seemed to trail back to my hibiscus, but I still wasn’t worried. I had looked at the hibiscus before starting and I could see some tiny little green bumps just beginning to push their way up from the very base of the previous year’s old stems. The plant had survived winter and I was very excited to see it grow.
Losing my Pink Elephant!
After tearing out the fabric, I rechecked my beloved hibiscus about a week later expecting to see that the green bumps had grown. They hadn’t. Instead, they were losing their green color. I checked again about a week later and I knew at that point that it wasn’t growing – it had died. I waited about another month, hoping that maybe it was just in shock, but would somehow pull through. It didn’t. When I finally gave up on it, I decided to see how many roots were growing into the native soil. I was beginning to suspect that I had damaged too many of its roots when pulling out the weed barrier fabric. Well, it turned out, it had NO roots still growing down into the native soil! I ended up killing one of my favorite plants without even realizing it.
Let the Rich and Poor Mix
The death of my hibiscus just goes to show that the soil produced when wood mulch breaks down is really good stuff! You don’t want this material separated from your poor, natural soil. You want that wonderfully, rich, organic matter to be mixed up with your existing soil to improve its quality (you can thank your earthworms for taking care of mixing the broken down mulch with your native soil!)
Use Bark or Wood Mulch, but Avoid Weed Barrier Fabric!
As your mulch or bark breaks down, you’ll need to replace it. You can probably re-mulch well every couple of years or so, or just top it off every year. I prefer to top off each year because it feels like it is less overwhelming of a job and I think it keeps the beds looking better. Don’t look at it as a waste when the mulch breaks down and needs to be replaced. If you have lousy soil, like I do, just think about how much rich, organic matter is getting worked into that soil each year! So go ahead and mulch those garden beds – and whatever you do, avoid weed barrier fabric!
Have you lost a favorite plant and don’t know why? Learn about one of the main reasons plants don’t survive Colorado winters.