Plastic Mulch

Last year I made garden beds on very poor, thin soil that was lawn.  Three of my 6 beds were on an old gravel parking area and had about 1/2" of topsoil over the gravel.  In preparation, I smothered the grass for a few weeks, laid 'compost' (it was pretty crappy quality) 3-4" deep, laid out my weeper hose and covered it all with black plastic I bought from Home Depot.  By the time I planted, every hole I dug turned up 2-3 worms where I hadn't seen any before.  It took about a month before the garden really took off, likely due to the grass that was still alive when I planted, but applications of worm casting and compost tea also helped.  

Prior to that, I'd used straw and chip mulch, but I didn't have the fiscal or time budget to go that route.  My preference would be not to use the plastic, but I have to say that it worked incredibly well.  I was working out of town 5-6 days a week (living at the job site), so I didn't have much time for garden maintenance.  With the plastic mulch, I only had to pull maybe 10 weeds all season and those had come up in the spots where my plants were.  The black plastic really helped heat the ground up quickly and I found I didn't have to water as much.  My tomatoes, peppers and tomatillos did very well without any row covers, which I attribute, at least in part, to the warmer soil temps.

I'm very much in favour of reducing plastic use as much as possible, but I still use a lot of it.  I am very careful with my seed trays and I usually get at least 3 years out of them, even though they're paper thin, I've got a bunch of plastic pots I bought used and there's the plastic tote for water and the hose and weeper hose.  I was renting so I wasn't going to do any swales and I didn't have time for that in any case.

Personally, I feel that I'm using plastic to do as much good as possible.  I understand that natural mulch is better in many ways and I have had great success with it, but I found the plastic mulch superior for weed control and getting the soil temp up quickly.  It's also a lot cheaper to use plastic if you don't have a source of free/cheap wood mulch and, believe me, I tried that avenue first.  I think that it's very possible to cut out a lot of the plastic for gardening, but water storage and irrigation are much easier to implement with plastic products, especially if you're just starting out on that site.  

Does anyone here use plastic mulch?  What are your thoughts, good and bad, about it?

I see this coming up a lot.
Plastic mulch seems to work.
The downsides seem to revolve around how it's born and how it does.
Oh,  and anything it leaches out in between.
Given that plastic seems to be found everywhere,we could just shrug it off, but how about finding alternatives instead?
~Silage plastic is super durable,  so it will last a long time.
~Hardboard is exploded/compressed wood fibers, and lasts a long time in contact with the ground.
~Basalt fabric could last a lifetime

I only have direct experience with hardboard.
It's the stuff pegboardis made of.
I lay it down for to suppress weeds/mud.
It doesn't roll up,and at 10 -12 bucks for a 4x8 sheet it's s lot more expensive than plastic, but it does last for years.

Another alternative material could be carpet.  I salvaged several rolls from a church renovation 5 or so years ago.  It was low weave grey or beige.  I first used it on my driveway for weed control, and it blended right in with the gravel look.  I've moved pieces around in order to establish new garden spaces.  It handily smothers meadow grasses to give me time to add amendments and structure.  These pieces are artificial fibers, so will eventually need to be landfilled, but they certainly are paying more utility than going straight to the landfill.  I haven't used them as permanent mulch, but I'll bet you could cut planting holes.  However, be aware that moles love to tunnel under the carpet in the field.  I've now got an old wool rug that I intend to use similarly, and will see how well it composts.

Whatever plastic film you use, do try to find a Trex recycler for eventual disposal.  My local Piggly Wiggly has a collection box, and I've recently become aware that it's not just plastic shopping bags they accept, but pretty much all films - https://www.trex.com/recycling/recycling-partnerships/

William Bronson wrote: I see this coming up a lot.
Plastic mulch seems to work.
The downsides seem to revolve around how it's born and how it does.
Oh,  and anything it leaches out in between.
Given that plastic seems to be found everywhere,we could just shrug it off, but how about finding alternatives instead?
~Silage plastic is super durable,  so it will last a long time.
~Hardboard is exploded/compressed wood fibers, and lasts a long time in contact with the ground.
~Basalt fabric could last a lifetime

I only have direct experience with hardboard.
It's the stuff pegboardis made of.
I lay it down for to suppress weeds/mud.
It doesn't roll up,and at 10 -12 bucks for a 4x8 sheet it's s lot more expensive than plastic, but it does last for years.

I agree that it's not without its issues.  I like silage plastic and billboard plastic because they'll last longer, but I've never seen silage plastic in black, so I don't know if it would be as effective in heating up the ground, which can be very helpful in cold climates.  I would look at hardboard, but I would think storage would be problematic for any sort of quantity and I think I'd be more worried about what would leach out of it than the plastic.  I'd have to do some reading up on the binders used.  Basalt fabric looks promising, but a quick search came up with a price of about $30/sq yard, which may never be in my budget.

At one place I built raised beds, a foot high, with a 3-4" base of my deep chicken litter.  The top bit of the litter was fairly hot, though the bottom was definitely composted to a good degree.  I then put about 8" of topsoil, topped it with rabbit pellets, and mulched with chips.  That worked incredibly well in all regards, though I did have significant weed pressure with only an inch of mulch.  I didn't have that option for the next garden, hence the plastic mulch.

Hi Ruth, I've seen some people mention using carpet.  I think it would be great for small areas but very cumbersome for a garden of any size.  If I had some I'd put it to use, but I wouldn't bring it in.  I'd be more worried about leeching from carpet than plastic.

I have been using cardboard with great success and it was free, almost.  I may have had to pay shipping on the things I bought that came in those boxes.  It is also a way to recycle it and not put it in the landfill.

Here is a thread that might be interesting:  https://permies.com/t/85144/Worst-Decision-rid-pieces-landscape

I have had luck with a rug made of natural fibers. Laid it on the ground and the weeds grew up through it. I ripped it up quickly and most of the weeds came with it. Immediately laid it on another section where the weeds were already up. I put it upside down so that the roots would dry in the sun. It was a pretty small test but it worked.

Women go to salons to have a similar thing done with wax.:-)

I wouldn't use carpets that weren't natural fibre throughout. That's essentially like sprinkling your soil with microplastics.

I would be interested in how remediation would go with that. Would oyster mushroom slurry work to break down the plastics in the soil?

I would go with cardboard. I think the absolute best cardboard to use is some that can't be recycled, like pizza boxes, or anything else that is "contaminated" with something that's just soil food, but would muck up recycling processes.

One thing I have been thinking about is vegetable-based transparent plastics. I don't know much about them, but I have seen, for instance, transparent rolling papers, a novelty smoking accessory, that were completely food-grade, and completely transparent. I would have absolutely no qualms about using plastic mulch in the field if I knew that after a lifetime of weathering, whether that's a season or ten, that it could be left in the field to be degraded, frozen, and broken to tiny bits, and would become food for soil organisms that would return it to the soil.

But I would want hard data on how these vegetable plastics degrade and are digested. If they turn out to be as bad biologically as the petroleum-derived variety, I think I would use cardboard. I might consider a longer-lived, more durable vegetable plastic, in that case, as a more sustainable glazing option than one derived from petroleum, but only if the processes checked out to be not harmful and ultimately sustainable.

-CK

Chris,

I hadn't even been thinking about the carpets shedding fibers.  I'll have to examine that.

you said:
"One thing I have been thinking about is vegetable-based transparent plastics. I don't know much about them, but I have seen, for instance, transparent rolling papers, a novelty smoking accessory, that were completely food-grade, and completely transparent. I would have absolutely no qualms about using plastic mulch in the field if I knew that after a lifetime of weathering, whether that's a season or ten, that it could be left in the field to be degraded, frozen, and broken to tiny bits, and would become food for soil organisms that would return it to the soil."

I have experimented with a plastic drink cup and lid that were advertised as compostable.  (I'm assuming plant-based here)  I set it and a regular plastic cup side by side.  They each contained and were sitting in soil and water, and weather exposed.  It took 5 years for the compostable cup and lid to disintegrate, but they actually shattered into tiny shards.  Not encouraging.

(sorry, can't figure how to properly use the quote feature.)

I've had good experiences using whole, non shredded, fall leaves. They tend to mat together and block out the majority of anything trying to get through with a pretty small layer. They are also usually darker in color too, so like you mentioned above they can slightly warm the soil.

I had a difficult time removing black plastic and landscape fabric that was leftover from the previous homeowner when we bought our home.

This thread talks about some of the difficulties with using black plastic. https://permies.com/t/85144/Worst-Decision-rid-pieces-landscape

I like that with using leaves, I can put it down and forget about it, and I don't have to worry about things later, and if i need to add more mulch, I can put more right on top of it, and it's also building nutritious leaf mold too for healthier plants!

Here's a article from Forbes about some if the effects of plastic in the soil

https://www.forbes.com/sites/linhanhcat/2019/05/01/microplastics-changing-agricultural-crops/amp/

Not all bad news,  but still no reason to promote moreplastic our environment.

Don't get me wrong, I'm not a proponent of plastic, but I want to get started with about 1/2 an acre.  I sure don't see carpet or even cardboard as a viable way to do that, and when faced with buying chips, I don't have the resources to do that.  I'm not talking about a long-term solution, but a way to get started on land that is currently in grasses/weeds.  

My experience with several methods of smothering and mulch leads me to believe that plastic has some overwhelming advantages.  I've found that 6mil plastic can last for at least 3 years, can be purchased at a fraction of the price of other options, helps heat up the soil, is very quick to put down or take up, and doesn't take up much space when stored.  To me, that makes it worth using to be able to grow food for me and mine and hopefully sell to others.  I do think that intent and use should come into play; does the benefit outweigh the harm?  If plastic mulch is a no-go, then do you have to avoid hoop houses with plastic, greenhouses with the same, plastic irrigation, etc?  Conventional ag doesn't use plastic mulch, that I've seen, yet I don't think anyone would claim that it's better than my use of plastic mulch, all things considered.  

After a year of growing, I hope to be able to mulch naturally for the most part, but plastic still seems to be better for smothering beds or covering them temporarily.  I also think that it may have a place with some leaf crops where chip mulch can't be spread thickly enough to smother weeds without smothering the crop.  

I would be interested in how remediation would go with that. Would oyster mushroom slurry work to break down the plastics in the soil?

Chris, I think they would, but they would also quickly degrade your cover too. I have a raised bed garden of trees inoculated with oysters, will have to see how they do. The best mycoremediation fungi are fairly high temperature "oysters" and I don't know if pleurotus would be as effective. I suspect they would do it, but slower.

I've used all the suggested mulches listed in the thread above—black and clear plastic, wood chips, and card-board—everything but carpet.

For every situation, there is an appropriate tool.  This includes plastic mulch.  For stubborn weedy areas where I don't want to cart in wood chips or other organic mulches, I'll use black plastic.  It usually doesn't stay down for longer than 2 months at the most. but it's a very effective way of smothering weeds and channeling water to flow where you need it.

Perhaps some day they'll find that prolonged use of black plastic mulch leaches something horrible into my soil, but I don't see any evidence of that.  I don't use it very often, but if it's the right tool for the job, I've got no moral or biological qualms about using it.  As for the small amount of oil that is required to manufacture a roll of plastic, there are a zillion other places in most of our lives that we use petroleum-based products, internal combustion engines, electricity produced by fossil fuels, and plastic containers of all types.  If I draw the line at "no black plastic mulch", then being logically consistent, out goes the garden hose, the 5-gallon buckets, and a pretty much every other thing I use in my garden that also contains elements of plastic.  Just being consistent.

If it's good enough for Stefan Sobkowiak, it's good enough for me.

https://beyondorganicnztour.files.wordpress.com/2015/02/permacultureorchard-answers.pdf    

This is another plastic type mulch but more sustainable just because it's long-lasting and a waste product.

EPDM Rubber roof lining material and pond liner often become unsuitable for their original purpose due to leaks. This material can be laid out to smother weeds when creating a new garden. I don't think I would ever want to leave a plastic mulch in place for the season, just as a means of killing grass and other weeds, early in the season.

Scrap sheet metal is another choice for short duration weed killing. Metal heats very quickly in the sun and  can kill most ground covers in a few hours. This is best done on a clear hot day.

Like Dale said, I have used corrugated metal from old barn roofs and metal buildings to good effect to kill weeds at the beginning of the season. Depending on age, you might need to worry about old lead paint. Also, I use the thick black plastic from old cow troughs (the kind with metal legs holding a long bent piece of plastic). The plastic flattens out once the trough legs rust and fall apart. It doesn’t disintegrate like most plastic mulch and I can find some in a lot of pastures and farm dumps around here.

I think a waterproof mulch layer could be a problem unless you want everything in the area to die from lack of water. I used cardboard in my front yard about 2 years ago, and this spring as I dug in to plant I discovered there was a fine plastic mesh remaining. So I guess I should have tried tearing up the cardboard prior to using it to ensure it didn't have plastic in it.

Ah, I was thinking of a kill mulch—normal mulch, definitely not waterproof!

Today I called a local  coffee roaster, looking for free burlap to start a green roof.
They had no pure burlap handy,  but they did have plastic  lined sacks,  and they had something called coffee chaff.
The internet says the chaff is kinda waxy and semi-water repellent,but breaks down eventually.
Kinda like matted autumn leaves.



Stefan Sokowiak has a permaculture orchard that uses plastic.
He has had it so long that that there is a 4-6" layer of soil atop the plastic layer.