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I know there will be differing opinions on this subject, from different people. I, for one, have always used bark mulch, and can attest to the fact that when used properly, it will build soil and grow healthier plants (ime).I have also heard that a layer of plastic, covered by gravel, is the best mulch. To me, it seems that this can only depreciate, and doesn't build soil at all, and may even leach chemicals out of the plastic into the ground. And then there are those who think that undecomposed mulches are bad, and you should go with compost. imo, compost is one of the best things you can add to soil, but doesn't take the place of mulch.

So, why are there differing opinions from experts? Shouldn't people with experience come to a similar conclusion? Or do different ways work comparatively well enough that it's pretty much whatever you like better?

Please don't answer if you feel like arguing with someone, just lay out what your reasons are for why you use the mulch you use, and your experience with that mulch.

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Won't pros and cons vary depending on things like climate and current soil condition? –  Alpar Aug 20 at 8:39
    
@Alpar yes, which makes it useful that so many users answered. –  J. Musser Aug 21 at 21:21
    
Thanks for starting this conversation I am finding it very helpful. I think I am leaning away from bark mulch due to this and other sources. –  treeNinja Aug 27 at 14:13

6 Answers 6

I have never heard of anyone recommending a layer of plastic with something over the top, gravel or anything else. Plastic will stop water permeating the ground, and any gravel on the top would be floating! A layer of permeable membrane (geotextile fabric) with an ornamental mulch (pebbles, gravel, limestone chippings, slate, pea shingle) keeps weeds down, moisture in and can give a decorative finish in certain types of garden, particularly urban environments, but does not contribute to the soil, as you've said. It's also not exactly a permanent solution to weed growth either, despite what everyone says - soil particles inevitably end up in the topping, allowing weeds to germinate, and if left, some of those weeds will actually root through the membrane (couch grass in particular).

Because most of the ornamental gardens I've worked on are small in comparison to many in the USA, my personal preference is always an organic mulch, usually composted animal manures or good home made garden compost or composted leaf mould rather than bark. These break down quicker than bark, yet if laid 2-3 inches thick on damp soil in spring, will do a good job of keeping down weeds throughout the growing season, and keep moisture in. It's also humus rich, so as it breaks down, the soil will be enriched without the need for digging, which is a bonus both from the point of view of my back, and the structure of the soil, which will not then be constantly disturbed by frequent tilling/digging to remove weeds and break up any panning which may occur after irrigation. I'd usually replenish the mulch annually or biennially.

Bark chips I reserve for wilder areas, or very large gardens, particularly around large, mature shrubs where there is little groundcover in terms of plants.

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So more of a compost user. Good. Very interesting. –  J. Musser Aug 20 at 20:56

For ornamental use

  • In my area, the most common mulch for landscaped ornamental beds is premium shredded bark mulch (my source)

    enter image description here

    It's very nice to work with, is partially decomposed (usually very hot when I get it), decomposes in about a year (when I reapply), and adds to the organic matter content of the soil. The earthworms appear to love it, and will go up through a pile that cooled off, and turn it into compost. It does keep weeds down exceptionally well. It is a byproduct of the sawmill. The biggest cons are that it fades within two months, and forms a moisture barrier when laid too thick.

  • The second most common mulch for ornamental purposes is black dyed mulch. Because the dyed mulches are so similar, I'll cram them all in here. (my source)

    enter image description here

    I hate this stuff. it's so unnatural, looks poisonous, and takes way too long to break down. I think they make the dye by burning coal tar, to get 'carbon black'. I never use this on my own property, and only use on others properties if they can't accept something else. Is does go on easily though (one pro) :/.

  • The last one used locally as ornamental is cocoa mulch. (my source)

    enter image description here

    This stuff is extremely expensive, and doesn't last long, but it builds soil and adds OM. I usually have to apply twice a year, to keep a good weed barrier, making this even more expensive.

Soil building/Edibles

  • Grass clippings are big soil builders, and I use all the grass clippings I can find.

    enter image description here

    Besides going into the soil quickly, adding lots of nitrogen and OM, they form a mat that seals in moisture, prevents weed germination, and keeps the soil temperature even. It is a great mulch for most vegetable garden plants. The only cons - It burns when piled too deep, not a problem for me. And, depending where you source, there may be pesticide residue on them.

  • Straw is a good carbon mulch, which I use more for winter protection and composting.

    enter image description here

    I get this very cheap from local horse farmers that it spoiled on. Mold isn't good for horses, but it's one step closer to where I want it. It's great for strawberries, veggies, even fruit trees. It pulls a little nitrogen while decomposing, but no big deal, the nitrogen is suspended in the new humus for future plant use. The same goes for all carbonaceous mulches. Cons? Not many. It can be hard to lay if you're not used to it.

  • I live right in the middle of mushroom country, so mushroom soil (byproduct) is cheap and valuable.

    enter image description here

    This has a high nitrogen level, and is a great addition to soil, compost piles, or used as mulch. It is cheap, brings OM from outside, so you build fast. It basically starts as a horse manure compost pile, and the mushrooms break it down into what you buy. Great for mulching, or adding directly to soil, as a conditioner. Cons: It smells like crazy a day or two after spreading (because of the nitrogen content).

  • Hay is a good mulch, with a balanced c/n ratio for compost (around 30/1).

    enter image description here

    Spoiled hay can be used as straw, and is usually free/almost free in my area. It goes down easily, and builds soil fast. I usually use alfalfa hay, cause it has a higher N content. The biggest con is that badly grown hay (the cheap stuff) is likely to have weed seeds, possibly weeds that aren't currently in your garden.

  • Shredded leaves are higher carbon, and last longer. They work well for root protection.

    enter image description here

    Leaves should be shredded before use as mulch, so they don't mat down. I use them for invasives control on the woods edge, and under shrubs. Evergreen needles can be used as well. Leaves take a long time to decompose, so they should not be stirred into the soil.

  • I use composted animal manure as a mulch in my vegetable gardens.

    enter image description here

    This is costly in my area (I don't have time for many animals anymore), but IMO entirely worth it. This is about the best soil builder there is. It is balanced, rich, high in OM, and basically good for plants. Composted properly, there is no smell or weed seeds. There are no cons.

Inorganic mulches

  • White marble pebbles on geotextile fabric

    enter image description here

    This is one of the only cases of non-organic mulches in my area. I find this mostly around newer commercial complexes with a few shrubs growing through. It really looks good for only the first couple years, before the pebbles get green and dirty, and weeds find their way through. Also, taking this stuff out is a mess.

  • White marble pebbles on black contractors plastic.

    enter image description here

    This is a very bad idea, because is completely cuts the soil off from air, water, and light. I've only seen these a few times, and they were a mess. Don't ever do it.

  • 1/2 inch landscaping gravel on geotextile bed.

    enter image description here

    This lasts well, and I've seen good results when used in walkways, but it is bloody hard to get under, without getting some in the soil. I usually use/see this around buidings and in walkways. It also costs quite a bit initially.

The mulches listed above are the main ones in their category that I worked with a lot. Obviously, the mulches in the soil building/edibles section is limited by imagination, and there are many good suitable mulches. I've listed the few that I use a lot, and left out some that are too localized, or are generally horrid ideas. :)

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We have gone through a number of mulches with various results.

  • geotextile landscape fabric and peastone gravel. Looks good, if a good quality fabric is used, resists weeds for many years. Very hard to plant things in and almost impossible to improve the soil underneath and leave the fabric/stone in place
  • bark chips: not as cheap as they used to be, popular with earwigs, you need to wear gloves when working with it as bark splinters in your hands are painful. Fades over the years and needs to be renewed
  • leaves mulched with a lawnmower work great. After being cut up they break down in one or two seasons and stop weeds quite well. Has to be renewed and does not have that crisp aesthetic look some people like
  • white marble chips: some people like them but they get dirty with a green algae growing on them
  • pine needles: our current favourite, available for free from most people who have a lawn with a mature pine tree. Nice orange colour fading to a light brown with time. Slowly breaks down and may make the soil more acidic. When newly applied a strong wind will blow some around but as it packs down this is not a problem.
  • cedar mulch: when on sale at the garden centres this is a cheap and long lasting mulch which keeps the weeds down and has a nice neutral colour
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So you're more of an undecomposed om user. Kinda like me, but I usually have to put down what customers have/order. –  J. Musser Aug 20 at 20:55
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End use is an important consideration. High traffic walkway areas benefit from a fabric/inorganic mulch like peastone or gravel, garden beds are easier to deal with when mulched with an organic mulch. –  kevinsky Aug 20 at 23:16
    
The bark mulch you're familiar with is probably different than what I'm used to. You describe it as 'bark chips' which seems different than the stuff I use (see my answer). –  J. Musser Aug 21 at 21:30
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Pine needles do not have a measurable affect on soil acidity. (See my comment on this answer for cites gardening.stackexchange.com/a/13782/3473) –  Philip Aug 21 at 21:36
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@Philip See my question here gardening.stackexchange.com/q/13789/499 so we can explore this question in detail –  kevinsky Aug 21 at 23:56
  • My absolute favorite mulch, feared by some (only legitimate if you go too thick at once, when it will start to heat and slime) is lawn clippings, about 2-3" deep. Looks very tidy, breaks down well, stops weeds fairly well. It's robbing the lawn to feed the garden, but that's an OK trade in many households. Dead easy if you have a bagging mower.
  • My blueberry/acid bed is mulched with pine needles - lots of pines and a large deck handy, so they are easy to get with a broom - you can also import "pine straw" in bales, but I suspect that runs to money quickly. Any tendency to acidity is desireable here. They could stand to break down a little quicker than they do, from the POV of soil nutrition, honestly. For a non-acid bed you could lime under them; I toss sulfur into the blueberry bed from time to time for the opposite effect. If you wanted to build nutrition faster (dubious in a blueberry bed, which are sensitive to over-fertilization) you could fork most of them off, add compost (& lime if wanted), and fork them back on.
  • I've had the misfortune to have a bed done with landscape fabric and bark mulch thrust upon me - it was horrid, from a plant point of view, under that plastic layer. I ripped it out within a year or two. Rarely have I seen such dead soil, and there is no way to do anything for it with the fabric in place.
  • I use shredded paper and sheet newspaper in the vegetable garden for keeping weeds down, especially on paths. The shreds are OK around plants. While there is some concern for robbing nitrogen while it breaks down, IMHO it's limited if the material is ON TOP rather than mixed into the soil. I think I have read of folks using rolled brown kraft paper (thicker than newsprint, no seams) in the same manner that rolled plastic mulches are generally used, but without the plastic disposal issue at the end of season. Have not tried that one personally yet. Newspaper does NOT look good unless you have enough of something else to bury it out of sight.
  • Cocoa hull mulch smelled wonderful, looked great for a little while, was expensive and imported, and proceeded to mold in short order
  • Not really a fan of bark mulch, as it's trending towards stuff that breaks down far too slowly; and I find the dyed colors somewhat over the top, really. Straight woodchips make a nice path if you have a supply, and renew them occasionally.
  • Straw is nice if you can afford it (expensive and imported here) - hay tends to have too many weed seeds to be much fun.
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Nice list. I also rank lawn clippings very high. –  J. Musser Aug 21 at 1:51
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Pine needles do not have a measurable affect on soil acidity. Uncomposted pine needles have the same acidity as rain water, which of course doesn't make your soil more acidic every time it rains. wildlifegardeners.org/forum/feature-articles/… davesgarden.com/guides/articles/view/2702 –  Philip Aug 21 at 21:34

I am particularly fond of organic solutions for most everything we do on our farm. What I'm ultimately trying to do is improve the fertility of our soil and add as much organic matter to this otherwise heavy, red Virginia clay.

I lean toward mulches that I have here on the farm - grasses and shredded leaves. These are "free" to me and are quite effective at suppressing weeds and they break down readily - this is of primary importance to me because at the end of the day, it's all about the soil.

Straw is something we import onto the farm. I'm a big fan of this for keeping weeds under control in the veggie garden. I mulch heavily around the tomato plants and the straw holds in the moisture - I've watered my tomatoes only 4 times this season after they went in the ground and the straw has kept things moist. I put several inches of straw down and it works swimmingly well. It is not free but its cost is well worth it as it frees me from doing any weeding among the tomatoes. Straw runs perhaps $5 per small bale so it can get expensive quickly.

Spent hay is a good substitute for straw mulch - I use it sometimes and there are no weed seeds by the time I'm using it. It breaks down quickly though.

I've used kraft paper - it works OK - and newspaper but we generally shred the newspaper to mix with wood shavings for our rabbit hutch. So we don't use newspaper much as a mulch. And kraft paper isn't free so I tend to use that sparingly.

Around my beehives I use spun poly weed fabric, pinned to the ground. It does a reasonable job at keeping weeds and grasses from growing up around my hives and that cuts down on the pests causing problems in my hives. I have used it as walkways some but primarily I use it as a floor covering in my high tunnel hoop house for the walkways.

We compost everything we can here. I have four large bins made from pallets and wire fencing. This compost is a key ingredient in my soil improvement efforts and it is very useful as a mulch in some places. The price is right and that, for me, is very important.

Bark mulch breaks down slowly - which is good or bad depending upon one's view and intended use. For paths it works well but I don't like it in the veggie garden - that's just my POV and I know some folks swear by it. The big negative for me with bark mulch is that I have to purchase it and I'm not fond of that. We do buy some for the rose bed but that's it.

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Nice answer. I see this is mostly on edibles. I don't use tree (bark/chips) mulches in veggie gardens either. I usually use grass clippings and/or straw (which I can get for almost free when it's badly spoiled, and it still works). –  J. Musser Aug 21 at 1:43

As humans build developments, homes, malls, roads and parking lots, they strip off the topsoil leaving the top of our urban and suburban areas virtually sterile. Deserts have more life in their soils than our cities.

In order to sell properties after homes and offices were built, contractors simply used the cheapest path to landscaping. Bought the cheapest plants, plants on sale by nurseries because they'd been in a pot too long, stuck them in by the foundations and front doors, put sod down in front yards and worse, installed bark to cover the bare subsoil and 'keep the weeds down'.

People learn aesthetics. Most people relate bark with a new home, a new development. This look is popular and well-known. After purchasing their home they continue keeping bark on their soil 'to keep the weeds down' and because it looks 'new'.

There are a few contractors out there that put back some topsoil. They are rare. This practice has literally turned our urban landscapes into deserts. Some people who understand plants and soil know they need to improve their soil and do a little composting, or throw coffee grounds around but that is about the extent of undoing the sterilizing our development practices have caused. The timber companies make money, the fertilizer companies make money, sod companies make money and plant nurseries make money as we continue to replace dead or dying plants and lawns and dump non-decomposed materials on top of 'starving' soils just 'to keep the weeds down'.

Now, there is a plentiful product out there that can turn soils back into thriving communities, bring our birds back to our neighborhoods and make our landscapes lush with healthy plant life AND 'keep the weeds down'...

This renewable and plentiful product is human manure. We already know steer manure and chicken manure but although these products are great for our soils they also have a lot of weed seeds, are in differing states of composition, have varying amounts and types of medications and antibiotics and aren't tested. They don't look very uniform and aren't used for top dressing. Mostly used for vegetable gardens.

Human manure is mixed with a fine sawdust and decomposed under strict guidelines by our government. It is tested 5X. When it is completely decomposed the final product is NOTHING like its original ingredients. Chemically totally different. For one thing, it smells wonderful. (If it doesn't someone has by-passed the government somehow and it is not completely decomposed, don't buy it, don't use it!) The properly composted stuff is high in nutrients (you have to reduce your fertilizing routines a bit), a gorgeous NATURAL dark taupe color that is very fine in texture. No sticks, no stones, no pesticide residues (a huge problem found in mulches using homeowner lawn clippings and landscape debris), no weed seeds!! Maybe Grizzly Adams's manure has weed seeds but highly unlikely in our societies' manure.

All one has to do is install 2 inches on top of their soil and weeds, keep away from the trunks of trees and woody stems as you should do with any mulch and one's job is done. Soon organisms make a home in your soil and proliferate. Organisms in the soil have a symbiotic relationship with plants. They bring nutrients to the roots and the plant gives back carbon. Instead of waiting for hundreds of years or longer for topsoil to be made it is done within a year. Even non-gardeners will be able to see the difference in plants after just one week.

Anything that blocks the light from seeds will stop germination. Still weed seeds are blown onto our properties, bird droppings are full of seeds. There will be weeds growing on the top of any mulch. Not from beneath unless the mulch was thin. But oh so easy to pull out.

The tests show, no surprise, that it has a higher level of heavy metals so it should not be used on vegetable gardens. Of course most of the rest of the world has always used human manure, raw, to fertilize their crops. They have been spraying our skies with heavy metals for over 60 years playing with changing the weather. News to you? Look it up.

Ideally, this stuff should be replaced every year. Every other year even every third year works just fine. The companies that make this stuff usually have a service where it can be blown in on your beds. They are very neat and tidy! The more sterile your soil the faster it disappears as the soil organisms eat this stuff, take it down into the soil and poop it out. They do all the mixing and aerating a healthy soil needs. No need of any help from us humans. In fact, the tilling of our soils is an enormous CO2 source in our atmosphere. Don't believe me? Check it out. Being lazy in this case, albeit smart, is the best way we can improve our environment.

Admittedly I was spoiled. I used this stuff exclusively for 30 years. I had to do a lot of re-education and still most my clients were hesitant. But, when their neighbors saw the difference they'd try it. No one to my knowledge went back to the out-of-fashion, ugly (too coarse of texture and unnatural color detract from the look of a landscape), and does nothing for the soil except deplete nitrogen but it does 'keep the weeds down' as good as any mulch would.

The use of plastic beneath mulch is the worst sin a landowner or landscraper can commit under the guise of 'gardening'...in my opinion. Unless one is purposefully solarizing with plastic this practice should be illegal. For reasons of cruelty to our domesticated plants and harming the environment! It is purely ignorance. Landscape Fabric was never meant as 'weed control'. It was designed to keep gravel from disappearing into the soil. They just found another way to get people who don't know any better to give away more of their money and called it Weed Control Fabric.

Unfortunately, until we get everyone to understand the basics of our natural world and start to demand this human manure plus sawdust decomposed organic mulch, I have found it isn't that available. I did learn that they were drilling holes in our agricultural lands and pouring the raw human sewage UNDER the top soils and into our water tables. Why didn't we wonder what was happening with this stuff?

Well, we should start demanding this mulch be made available as decomposed mulch, NOT hidden in our water like they have already done with the poisonous Fluoride they told us was for preventing dental caries (BLATANT LIES). It won't happen over night. As more of us try this stuff and get the word out, it will happen. We have to put life back into our soils. Anything that is organic and completely decomposed will work.

In Rome they used lead in their pipes and in their cooking tools. This may sound like a small thing but the use of lead in the pipes of Rome is what they think caused The Fall of Rome. These weren't stupid people but they had got to a point where everyone became specialized. They didn't have anything else that was affordable and worked so well. They must have known lead was poisonous but didn't know that it accumulated in bodies. Similar things happen still today. Heck, we used leaded gasoline! Lead in paint! Still have Fluoride in our water. We can't afford to lead such specialized lives that others who just want to make money use our ignorance and could care less about the health of our bodies and more importantly, our environment.

I'll include a copy of a brochure from the company that produces 'Gro-Co' (their name for this mulch) in Seattle, Washington, soon. We've just relocated to Oregon and as yet to find someone that produces a similar product. If anyone reading this uses this stuff, please let us know your thoughts and experiences with composted human poo as well as your source!

I am horribly allergic to bark but that isn't the reason I won't use it. I hope you understand why I won't use it and that you will question your use of bark for mulch or any other non-decomposed mulch. Do your own research! Prove me wrong! Bark is Bad!

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Very thorough. I believe GroCo™ Soil Conditioner & Mulch is manufactured by Sawdust Supply Co., Inc., in Seattle, Washington. –  J. Musser Aug 24 at 23:13
    
yes, that's them...I'll scan their brochure and put it up... –  stormy Aug 25 at 17:37
    
Maybe not the brochure, it would look like spam. It's better to support an idea or concept on this site rather than a specific business/industry. Now you could put up a link to their brochure. –  J. Musser Aug 25 at 17:53
    
Makes sense...sure hoping there are more sources out there...grin! Wow. Oh, bark could be used to make paper...great for walkways and driveways to reduce dust, play areas. Be back later. –  stormy Aug 25 at 22:10
    
The link you posted above is good. Better than brochure anyway. Few things they say I disagree with but great product. They sell bark, lots of bark as well. Need more pictures of this stuff. –  stormy Aug 25 at 22:13

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