Black Plastic Mulch: Weed Free Gardening
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A couple years ago, after a sob session about my very large garden once again being taken over by weeds, a friend shared with me her tactic for keeping a weed free garden for over 20 years: black plastic mulch.
We decided to try it last year. Friends, I don’t think anyone will convince me to go back to gardening without it.
What is black plastic mulch?
Black plastic mulch gardening basically refers to laying a black plastic film over the space you are using as your vegetable garden so the plastic can prevent weeds from growing. We cut small holes or long trenches in the black plastic in order to plant the things we want to grow.
Where do you get black plastic mulch?
You can head to Amazon or agricultural stores and buy plastic made specifically for this purpose. Be sure to pay attention to length, width, and thickness of the plastic. There are biodegradable black plastic mulch options available, but know that these options are usually very thin (.5 to 1 ml thick) and can be more of a challenge to work with than thicker options.
We headed to a nearby hardware store and bought a 20’x 100′ roll of black plastic, similar to this heavy duty plastic sheeting. The plastic we have used has been anywhere from 3 ml to 4.5ml thick. Because I put this over everything (and not just in growing rows or raised gardens) I prefer something thicker that will hold up to me walking on it.
Pros of using black plastic mulch
Black plastic warms the soil.
Spreading a giant sheet of black plastic mulch over your garden space will help warm the soil up. You know what this does? It helps your seeds to sprout faster. I’m in Minnesota and this is a big deal. Any jump we can get on our growing year is an itty-bitty miracle!
The first year we used black plastic mulch, I had cucumber plants popping out of the soil four days after the seeds had been put in the ground.
Like I said, itty-bitty miracle.
There are no weeds.
No weeds, friends. You’re covering and smothering where the weeds would normally be growing. They can’t grow if there is a black plastic sheet over them.
Okay, to be perfectly honest, the only place you might have weeds come up would be in the holes you have cut in the plastic to plant your seeds or started plants. The trick is to a) not make those holes or trenches any bigger than they need to be and b) spend a couple minutes poking around every so often to nip off itty-bitty weeds that do start.
But honestly, the weeds have.not.been.a.problem since we’ve started using this method.
Your plants won’t be choked out by weeds. You won’t be searching through a forest of overgrown weedy-ness for those plants you thought you planted but can’t seem to find. Your plants will be healthier when they aren’t competing for nutrients with their friendly neighborhood whatever-that-weed-is-called.
(By the way, what are you planting this year? And if you grow it, will your garden actually save you money?)
It’s actually a joy to look out at the garden. It’s not an overwhelming depressing mess. I enjoy gardening again. I mean, look at my garden!
Cons of using black plastic mulch
In full disclosure and honesty, there are a couple things to be aware of if you choose to use black plastic mulch on your garden. (And remember, some of these things are because we choose to lay the black plastic mulch over our entire garden, not just in the growing rows.)
More time planting
Because you have to cut holes or trenches in the plastic in order to plant your seeds or started plants, it does take a bit more time to plant. But it is completely worth it because have I mentioned, no weeds?
It’s hot to work on
Black plastic is hot to stand on. If there is anything you want to do in the garden, it’s best to try and do it when it’s cloudy, in the morning, or later in the evening.
It can be slippery
It’s important to keep in mind that you’re basically putting a giant slip and slide over your garden space. If it gets wet, it will become slippery. Be careful when you’re walking around. Or, you know, wear a swimsuit and make the most of it.
Before the plants are established, it’s a bit of work to keep the plastic down.
This was our biggest surprise the first year. We had bought garden staples and landscaping stakes with our sheets of black plastic assuming that this would be enough to keep the plastic on the ground.
It wasn’t. It might depend on where you live, the lay of your land, the consistency of your soil, and how big your garden is, but with the first windstorm we got, that plastic looked like one of those parachutes we all played with in gym class. The stakes and staples were trying their hardest to stay stuck in the ground, and they were mostly failing. Our black plastic mulch looked like a tent that was about to launch into the atmosphere. We grabbed every brick and concrete block we could find and even cleaned out my rock garden in an attempt to keep that plastic where it was supposed to be.
Once the plants are established (especially if you’re growing viney things!) this isn’t as big of an issue. Before that, it is very helpful to have heavy items on the plastic. Also, anything used in your garden that happens to poke into the plastic (tomato cages, trellises, t-posts for fencing) is an extra bonus!
Pro tip: the less seams, the better. Every seam is a place the black plastic mulch can potentially lift up in the wind. The first year we had a lot of seams. We planned differently for our second year and only had one long seam, right down the middle of the garden.
How to use black plastic mulch
Here is the way that we go about setting up our garden with black plastic mulch.
First prepare your soil. Whatever it is that you do to your soil before you plant, do it now. Once the plastic is on, it’s much harder to make soil amendments.
On a nice calm day (don’t even try to do this if there is a breeze) we spread out our plastic. This year we made our garden slightly smaller in order to only have to buy one giant sheet of plastic that we could cut in half (therefore only having one seam in the entire garden).
If you have a large garden this might require all hands on deck. Some people may have to lay on the plastic (it’s amazing what a little breeze can do) while other people are staking it down.
After landscaping stakes and garden staples are used around the perimeter and along the seam, we place large bricks around the perimeter and along the seam for extra wind insurance. We also place more bricks in random spots.
Our garden is fenced every year so that’s what comes next. We slam t-posts into the ground (through the plastic) which also helps to keep the plastic down. We then put our netting up. (If you’re fencing your garden, don’t forget to build a super easy garden gate!)
Then the garden sits for a few days until I’m ready to plant. I like to have that soil nice and toasty.
How exactly do you plant your garden if it’s covered in black plastic mulch?
For something that you’re planting in rows…
Cut a slit in the plastic the length of the row that you want to plant. Then at both ends of the row, make another perpendicular slit so you have a “T”. (Don’t make it a huge perpendicular slit. Remember, the length of the slit will be the width of your row. The wider your row, the more chance you have for weeds to sneak out.)
Fold the edges of the plastic under, opening up the area you’re going to plant in.
Dig in (these Honey Badger Gardening Gloves work great!), loosen the soil, drop your seeds where they need to go, and cover them up again with soil. It’s okay if you get a little crazy and some of the soil spills over on the plastic. It’s just one more thing to keep that plastic where it’s supposed to be.
You can add more bricks/staples/stakes along the spaces you’ve cut if you’d like. Keeping the plastic where it needs to be while those plants are getting started is super important.
For something you’re planting in hills (or a plant that’s already started)…
Cut an “X” in the plastic where you want the hill to be (or the started plant to be placed). Fold the edges of the “X” under so you have an open square.
Dig in, loosen the soil, pull up a mound of dirt to make a hill, and plant your seeds (or dig a hole and stick the started plant there). Again, you can use extra bricks, staples, or stakes around this new hole if you’d like.
And how do you water your garden if it’s covered in black plastic mulch?
A common question I get is how we go about watering the garden if we’re using black plastic mulch. Some people that use this method will employ the use of a soaker hose placed underneath the plastic. However, that requires knowing where you’re planting what before you lay down your plastic and I will fess up to you that I’m just not that organized.
When using black plastic mulch it is completely okay to use a sprinkler to water, although it’s a little overkill because you’re watering a lot of space that isn’t really going to get the water. Having said that, if you’re in for windy weather and worried that your black plastic is going to parachute off into the sky, running a sprinkler and letting the low spots of your plastic fill up a bit with water is an easy way to add weight and help the plastic stay put.
When we water, I just walk around with a hose or watering can and water the holes or trenches. It’s a nice way to spend 10 minutes (when it’s needed) and it gives me a chance to look closer at what’s going on in the garden.
Do you have any questions about black plastic mulch? Do you think it would work for you in your gardening set up? Leave a comment and let me know!