A lot of our customers ask us what they should do to prepare their yard for mulch. We always recommend pulling the weeds in the area first. A 3" layer of bark dust will then help to "shut the lights out" on the weeds below. But if suppressing weeds is your #1 goal then a weed barrier of some kind is even better.
There are a variety of cloths, plastics, and other materials that can be used to block weeds from growing. We even carry landscaping fabric in our retail yard. They vary in thickness and size and come in rolls to cover pretty big areas. They can be easily cut to the shape you need. But regardless of what you use, the goal for any barrier is the same: shut the lights out on anything growing underneath.
I decided to try the cardboard approach for the weed barrier in one of the beds in our office garden. This is something I'd heard about but never tried myself. Some of the benefits of using cardboard are:
It's easy to get. If you don't have a pile of it lying around somewhere, you can ask grocery stores or other businesses if they have any they can give you for free.
It breaks down over time. Unlike plastic or landscaping fabric which will often break apart and rise to the top, creating even more work and clean up in the future.
Oxygen flow to the soil isn't completely blocked. Meaning, plants can grow if you cut a hole in the cardboard. Worms and microorganisms don't die off.
Here's what the bed looked like before I began.
The first step was to clear the bed of weeds and try to level out the dirt. This was the most work!
Luckily, we've had a rainy spring so the ground was pretty soft.
I pulled the big ones out by hand then went over the entire area with a loop hoe. This cuts the smaller weeds at the root and helps level out the ground. I picked up a lot of the weeds but didn't worry too much about the smaller pieces since I'd be covering it with the cardboard anyway.
I rounded up some big pieces of cardboard and removed the tape and stickers.
I had read that wetting the cardboard pieces first would make it easier to work with. Actually, you can place the cardboard how you want it first, then wet it so you can shape it easily to your garden bed.
We have a drip irrigation system in this area, so I pulled it to the top in case I want to move it around in the future.
The next step was arranging the puzzle pieces to fit. I left a small strip in the middle for some dahlia bulbs I found while leveling out the area. We'll see if they come up!
Wetting the cardboard pieces here helped when I needed to shape it around the corners. I tried to get as close to the brick edge as possible.
Took a puppy break when Nellie came through 😍
Ok, back to work. We decided to go with fine fresh hemlock bark dust for the mulch. It's a really pretty color and we happened to have a lot of it around on this day. I was a little skeptical that it would blow away in the wind, but so far, a week later, it's staying put.
This is about a half cubic yard of bark.
To cover up the drip system I had to go about 3" deep, so this bed took about 1 yard in total. I also weeded between the bricks and cleaned up the edges. You know how it is - once you start it's really hard to stop!
I'm looking forward to seeing how long this lasts as a weed barrier and just how everything ages over time. There is one thing I'd do differently next time: excavate some of the dirt in the bed first. About 1 to 2 inches down. That way the cardboard would sit slightly below the level of the brick edging and the bark would be more flush to the edge. Nonetheless, I think it looks great!
What methods have you tried to block weeds before? I'd love to hear about it in the comments below!
~Heather in the office
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