Mulch vs 'Black Plastic'

I have heard the advice to shape mulch not in the shape of a volcano, but instead to shape it into a donut shape around plants many times, and it makes sense to me. The claims are that it allows the plant and soil to breathe, and reduces the chance of rot/pests. (Mulch also helps with water retention and breaks down into organic matter but my point in this is to talk about the shaping of mulch.)
My question is, how do plants placed tightly in black plastic so that just their stalks are coming out, survive? I wonder if it has to do with the kinds of inputs that these plants that should suffocate are being given? Would these plants grow and produce better if allowed to breathe?

I sometimes listen to a call in gardening radio show here in Canada and the expert consistently gives the advice that to cut back on some pests you have to break their life cycle. So he advises people that hygiene around their fruit trees is a big thing to keep up, since by taking away the pests' place of incubation (around the tree), you can break the life cycle. Again this makes sense to me, but how come in some permaculture paradigms placement of plant material around the base of plants is advocated? Are we promoting good AND bad organisms with this practice? Do we gain more on the positive side than we potentially lose out on the negative side?

-Full of questions in Canada.

Actually a good question. It's one of the those things where the benefits outweigh the negatives. Mulch may provide a place for pests to exist, but look at the positives it brings; keeps the root zone cooler/warmer, holds moisture in the soil, eventually contributes to the organic matter of the soil, keeps weeds at bay (which compete with young trees especially. So yeah, it may harbor pest, and if piled onto the trunk can kill the tree, but mulch properly used is vastly beneficial. I'd even go so far as to say it mimics nature. When a tree drops its leaves it's essentially mulching itself, the leaves help shade out other plants, slow soil erosion, and trap other organic matter in the root zone of the tree. Also, in a well designed system, the habit for pests also provides habitat for the things that prey on them.

Black plastic mulch doesn't suffocate plants either. To be fair it can solarize the soil and kill beneficials, but it retains moisture, eliminates competition, increases warmth to allow earlier growing, and the light reflected off certain plastic mulches (onto the underside of the leaves) has been shown to increase plant growth by exposing more leaf area to usable light. The slits where the plants come through the mulch allows plenty of water infiltration, especially seeing it's less likely to evaporate away once it's in the soil.

Thanks Blake, my intuition about organic mulch was fairly accurate, but I didn't know that black plastic could have some benefits. I will keep these things in mind!

Saying that mulching with organic materials mimics nature is half correct.

In nature, of course, a layer of organic materials builds up underneath trees but only in a minority of aleopathic trees does this layer eliminate everything else growing under the canopy and even these are usually selectivly aleopathic, allowing certain (theroetically mutually beneficial) plants to grow under the canopy. most trees do not drop a 6 inch thick layer of leaves that, while suppressing weeds, supports pests. In your position, I would more likely plant a cover crop than apply an organic mulch.

Something else that you may have overlooked, in nature, pest populations are largely controlled by predators. Some permies "introduce" predators by making a chicken pen around their orchard. Others forgoe the mulch entirely and pasture their sheep in the orchard. Or course, livestock comes with its own set of problems and chores and is unlikely to be very labor or time efficient unless you are already inclined to raise them.

Observing that organic mulching occurs in nature and coming to the conclusion that mulching therefore "mimics nature" would be the equiviant of observing that annuals thrive in areas that are dug up by critters and concluding that tillage mimics nature. It is one small part of the puzzle and without including the other factors, is going to present its own problems.

I'm not a fan of black plastic as it restricts both air and water from the soil/plants (although it does dramatically increase soil temperatures).

Mulch 'may' create a habitat for some pests, but it also creates a habitat for predators of those pests while it increases soil moisture, moderates soil temperature and will slowly break down to feed the soil food web.

I used to make tons of compost and vermicompost. I'd haul all kinds of materials, build heaps, turn and turn, then eventually haul to the garden*. I'm in my 60's now and it makes more sense to me to just mulch/sheet compost right in the garden and eliminate all the pre-processing WORK. Oh I'll prolly still make some compost heaps, but more and more I want to turn my garden into a worm bed and that requires a constant cover of materials....leaves, grass clippings, hay...In an orchard, or in perennial beds and foundation plantings, I'd use wood chips, but not in the garden except maybe for pathways. (wood chips are fine on the surface, but not tilled in as they would tie up too much N2 decomposing).

(*One fall many years ago I put a 12' ring of snow fence (about 4' across) in the garden and piled in (mostly maple) leaves 3-4' and just let it set over winter. I removed what was left in the spring to till. My ground was tough and tilling was a chore back then...but when I got to the spot where the leaves had been, the tiller sank effortlessly to it's maximum depth. The soil creatures had tilled the soil for me. This was a huge lesson in the power mulch and of no till permaculture - just let nature do the work! [but of course, this requires a good cover])

One thing to not overlook with black plastic mulch is it will eventually break down, creating a mess. I know from experience as my garden was covered in the stuff when i moved in. It had been covered by soil and Bermuda grass and was so old that any attempt to pull it would just break a tiny piece off. I was cursing the person who laid this down to grow "organic" veggies and then did not think it was their duty to clean up their garbage.

I prefer living ground covers because
-they are alive!
-they perform the functions of other mulches
-they can be chopped and dropped to add nitrogen and organic material into the soil
-i will never have to pick them up and dispose of them
-they can be function stacked since they have flowers that attract bugs, can be used as medicinals, or they can simply be food
-did i mention they are alive

I know some people have good luck with plastic mulch and they view it as a necessary evil, maybe they produce more than people who use living mulches, i dont know, but if you put it down, please make it your duty to pick it back up. Plastic mulch is a form of littering if left to rot.

Zach Muller wrote:One thing to not overlook with black plastic mulch is it will eventually break down, creating a mess. I know from experience as my garden was covered in the stuff when i moved in. It had been covered by soil and Bermuda grass and was so old that any attempt to pull it would just break a tiny piece off. I was cursing the person who laid this down to grow "organic" veggies and then did not think it was their duty to clean up their garbage.

I have dealt with something similar, although it is definitely the case that not all plastic sheet mulches are created equal. Plastic fabric is terrible stuff. The logic is that a woven material will breath better and allow water infiltration. In practice the fabric breaks down into little strips of plastic fibre that get into everything and need to be picked out of the soil piece by piece.

On the other hand, in the Permaculture Orchard video they advocate using heavy duty black plastic sheeting and cutting slits to plant through. They showed in the video healthy soils and thriving orchard trees. This sheeting will not break down to small pieces, except over a very long time, and will be much easier to retrieve and reuse, as it is not prone to getting tangled with lots of roots and plant fibres. In their setting heavy black sheeting was a clear win over not using sheeting as demonstrated by vigor and yield of trees in adjacent rows.

dan long wrote:Observing that organic mulching occurs in nature and coming to the conclusion that mulching therefore "mimics nature" would be the equiviant of observing that annuals thrive in areas that are dug up by critters and concluding that tillage mimics nature.

What a great idea to add to my justifications for tilling... The one I typically use is: Since I am growing on river delta soil, and since the river traditionally flooded every year and laid down a fresh layer of soil, therefore I figure that now that the river no longer floods my fields that tilling is a close approximation to the natural conditions that existed in my garden before agriculture.

Yeah i remember the discussion about plastic mulch and permaculture orchard here. It is true that not all plastics are created equal, and the type can make all the difference in performance.

Honestly I did not get the dvd, but i was not really sold on the idea of plastic mulch from the discussion. I realize it works and functions excellently for many people, but i would rather design my systems another way. Ive seen my fruit trees growing and thriving without plastic mulch, so i know there are other variables at play. I live in a climate where woody mulches do not last long at all so i would call them temporary, just as i would call plastic temporary.
Companies can claim a specific lifetime of their plastic products, but plastic was only first invented in the early 1900s, any claims that a product will last 100 years is questionable at best.

My view is highly affected by the fact that i do not have a commercial orchard, so keep that in mind. If i was going into business i would attempt to design my system so i would not get to the point of needing plastic ground coverings. I would try every other alternative before going with plastic-including redesigning the system, just as i am going with every method to seal a pond before resorting to expensive plastic sheets.

Joseph Lofthouse wrote:
What a great idea to add to my justifications for tilling... The one I typically use is: Since I am growing on river delta soil, and since the river traditionally flooded every year and laid down a fresh layer of soil, therefore I figure that now that the river no longer floods my fields that tilling is a close approximation to the natural conditions that existed in my garden before agriculture.

I'll confess that I (too) still get my Troybilt tiller out once or twice a year (or more if/when I grow green manure like buckwheat or winter rye to till under).
However, I also realize that it upsets if not destroys elements of the soil food web. Now that I'm in my 60's and thinking forward to when horsing that tiller around won't be that much fun, I'm thinking more and more about no till. My 'plan' is to put enough organic matter into/on the soil (mulch/sheet composting) that the soil critters will do my tilling for me...after all, as nature (and permaculture) teaches us, nature doesn't till and things seem to grow just fine. I think the ticket is a good thick cover.

I'd like to weigh in with an additional consideration regarding plastic mulch: what is the effect on the nutritional content of the food grown under said mulch compared with cover crop or organic mulch? In a study designed to evaluate the effects of cultivation methods on nutritional content, sea buckthorn (Hippophae rhamnoides) was grown with plastic vs organic mulch, and the phytonutrient content of the leaves was measured via HPLC. Plastic mulch decreased the concentration of phytonutrients (gallic acid, hydrolyzable tannins, and condensed tannins) compared to the other mulches used. These phenols and tannins are the same constituents that give green tea its health benefits, and the reason I ferment tea from the leaves of the sea buckthorn I grow.

As an aside, a second finding in this study: The concentrations of phytonutrients—gallic acid, pentagalloylglucose, quercetin-3-rhamnoside, monocoumaroyl astragalin A, total hydrolyzable tannins, and condensed tannins—were significantly higher in plants grown on flat surface than on low hill surface. This finding may have some bearing on where on a swale one sites certain plants.


www.ncbi.nlm.nih.gov/pubmed/17002439

Hi folks! This is my first post here. Other than a couple of books I had back around 1980 I'd never heard of permaculture until a few weeks ago. I have been gardening for a long time and using some of what I now know are currently called permaculture techniques. This site is great! Hat's off to Paul.

My take on mulch around trees is that it all depends. First, my understanding is that it's not good to put the mulch right on the tree trunk because it draws little critters that may eat on the bark while hidden under the mulch. The other thing pertinent to the area right around the trunk is that not much tree activity takes place there. My take is that from about a foot away from the trunk to about a couple of feet outside the drip line is where you'd benefit from mulch. That is the area where most root action is taking place including uptake of water, oxygen and nutrients

As for plastic, someone already noted that plastics come in many varieties. The lowest quality is usually what you'd find at a lumber yard. I have some clear plastic (made for green house use) that has been out in the sun (intense sun at over 6k ft in southern Colorado) for five years already and is still useable. Even the cheapest plastic will last a very long time if it is completely buried. It's the sun that does it in. I don't know why you'd want to bury plastic, but I just thought I'd note this little detail.

The plastic fabrics also vary a lot. I had some a few years ago that was was to thin and to tight a weave to let much air through. I threw it all away. The Colorado state foresters sell a course rough plastic type fabric that is mostly used to start new trees on dry ground. I used it to start a bunch of junipers on dry prairie (20" or less precip). It worked well enough with about an 80% survival rate of bare root trees, but I consider it just a temporary thing to be pulled and pitched after the trees are established. Without that mulch I'm guessing that hardly any of those trees would have survived. I also put a stretch of snow fence along the west (wind) side to try to grab/hold a little more moisture.

IMO, the worst thing about plastic is that it's plastic… has to be manufactured and, someday, pitched.