mulch faq

Q. What is the purpose of using mulch in the garden?
Q. What makes good mulch?
Q. What do you use for mulch in your garden?
Q. When do I apply it, and how much should I use?
Q. Do I have to move the mulch before adding compost and fertilizer?
Q. Are cocoa hulls good for mulching?
Q. Can I use mulch made from recycled tires?
Q. Is black plastic or landscape fabric a good mulch?
Q. What about Ruth Stout’s mulch methods?
Q. Do you mulch your pots and other containers?

Q. What is the purpose of using mulch in the garden?

A. Mulch (such as bucketful, above, about to be spread) serves several purposes. It will not just suppress weeds and slow moisture evaporation, but should also break down into the underlying soil gradually and thereby improve the soil’s texture. A layer of mulch helps moderate soil temperatures. Mulch serves as a buffer from soil compaction caused by rain, and helps prevent the crusting-over of bare soil that can sometimes prevent moisture from being absorbed.
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Q. What makes good mulch?

A. This can be very confusing, particularly because what’s sold as “mulch” in many cases isn’t really very suitable for performing the full range of duties that I think mulch should accomplish (above). Briefly, I look for a material that is:

  • An organic substance (meaning deriving from some living or formerly living matter);
  • Fine- to medium-textured so it will break down gradually into the underlying soil…
  • …but substantial enough to stay put;
  • Preferably aged before I use it;
  • Dark in color, like soil is (if for the ornamental beds);
  • Available locally at a good price, preferably in bulk delivery unbagged;
  • Not a source of contaminants, pests or diseases.

To elaborate: Any mulch I use in my ornamental beds must be fine-to-medium textured and dark colored so it looks good. Forget anything that’s going to sit there and never break down, like big hunks of bark (which I call “baked potato mulch” because they look like giant spuds sitting on the ground to me), or anything that’s bright orange. I am completely opposed to dyed mulches.

One caveat: Very fine-textured materials like sawdust do not make good mulch as they can cake and fail to decompose. Even pure compost is not my idea of mulch–I put mulch on after a top-dressing of compost in spring.

Why use a product that has been aged or composted before you use it as mulch? That extra step really makes a difference in the mulch being ready to do its job as a soil-improver.

I used to use bagged mulches, including cocoa hulls and various bark products. I have since switched to local materials I can have delivered in bulk, sans plastic bags (and minus all the fuel used in processing and trucking of bagged stuff across the nation to my local garden center). Environmentally, it’s important to buy locally when you can, especially with bulky items.

Technically, plants can serve as a sort of living mulch as well; that’s why certain ones are termed groundcovers, but many other plants can shade the ground and help prevent weeds and so on. Landscape architect Claudia West famously has said, “Plants are the mulch,” and I love her philosophy (explained here).

Borrowing tactics from farming, cover crops (whether grasses, legumes, grains…) can also be sown as living mulch on idle areas of the garden to help keep weeds down and also then be turned in to add organic matter.
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Q. What do you use for mulch in your garden?

A. On my ornamental beds, I use a composted stable bedding product–a local agricultural byproduct from horse or dairy farms that has been allowed to age first. It’s simply wood shavings (not too fine, not too coarse, as you can see in top photo) that farmers spread on the floors of animal stalls to absorb manure and urine, and then muck out and compost afterward to recycle it. (It is composted “hot” to kill weed seeds in it.) I expect you can find a local source via your county cooperative extension office; this website give a sense of the kind of product I am talking about, though I buy from a local farmer in the Hudson Valley (at this link).

Leaf mold (partially rotted and shredded leaves) would also be great, if your local landfill offers it, or start a leaves-only compost pile in fall and pre-shred it like this.

In my vegetable garden, I sometimes use straw (which is of course not dark-colored), preferably chopped, or the rotted, shredded leaves. In rough areas such as along the roadside outside my fence, I will use wood chips from the power or phone company, or from a fallen tree. I will also use wood chips or bark chips on utility-area pathways (behind sheds, between vegetable rows).  I pile up wood chips and let them age before using them. Again: I do not use chips in my beds.

For more details about pros and cons of different mulches, try this fact sheet from e-Organic (part of the Cooperative Extension services).
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Q. When do I apply it, and how much should I use?

A. I mulch my perennial and shrub beds in spring, but not until after the soil has a chance to warm and dry a bit. I also am conscious of areas where I want biennials and other self-sown plants to have a chance to do their thing; mulching these too soon may prevent successful reseeding.

You want a 2- or 3-inch layer, generally speaking, and if you use the right stuff, about half of that will work into the underlying soil before you go to replenish in fall or the next spring.

Keep the mulch a couple of inches away from trunks of trees and shrubs; never pile it up, volcano-like, against them, as that can invite pests and diseases.

Anytime I work in an area and disturb the mulch, I add a bit more rather than leave bare spots. I apply mulch to new beds whenever I plant.

Mulch is sometimes also used in winter in cold zones to help keep newly planted things frozen solidly in the ground (applied after the ground freezes), or to shield tender plants from damage (such as the graft union on roses). For that purpose, materials like evergreen boughs (which would not normally be good for mulch) may also be used.
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Q. Do I have to move the mulch before adding compost and fertilizer?

A. If you use a mulch that has the correct texture and has been composted first, this should not be a problem. I simply “topdress” (spread compost and all-natural organic fertilizer right on top of last year’s partly decomposed mulch) then replenish the mulch as needed.

The problem with most mulches, even bagged shredded bark, is that they haven’t been composted before they are sold and/or are too coarse, so they don’t break down very well, but rather form a sort of coating on top of the soil.

Good mulch, on the other hand, breaks down and improves the soil below. I don’t mean it breaks down in a week or a month, but over the course of a season or two.

If you have a thick layer of mulch that’s not breaking down nicely, and the layer is just getting thicker and thicker each year, rake some away and then add your amendments and start using a new, better-quality mulch this year on top of that.
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Q. Are cocoa hulls good for mulching?

A. I used to use bagged mulches, including cocoa hulls, many years ago. I have since switched to local materials I can have delivered in bulk, minus the plastic bags. There is no cocoa-processing plant nearby and hence no local source of this recycled product.

Cocoa hulls can be very high in potassium, which can be a problem for some plants in some soils, and they may be toxic to pets (particularly dogs) if they are swallowed. So those factors added to the “buy local” environmental argument put them on my “no” list today.

Additionally, cocoa hulls are hard to spread and either blow away or clump together if the bag got wet (sometimes they can be moldy in damp weather, too). However, they have many of the qualities I want in a mulch: They are dark in color and fine textured and look good on the beds.
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Q. Can I use mulch made from recycled tires?

A. To me this is a real environmental no-no–yet another wacky thing that is being tried out on us unsuspecting consumers. Yes, it’s re-using worn tires…but putting them into the landscape, and nature, in shreds is as bad or worse as piling them up at the dump whole. They don’t break down and become incorporated into the soil, so they’re no good, and even dangerous. Remember that animals and much smaller living organisms interact with and inhabit the soil–I don’t think a worm wants to process tire shreds while making worm castings, or a robin wants to rustle around in the tire litter (though they love the leaf litter!), or worse: choke on a piece mistaken for something to eat.

My rule: To be a mulch, it must be organic (a living/formerly living material) so it can decompose over time and return to the soil, not taint it. The one exception to my mind re: the organic rule would be some stone materials used in certain zones and certain types of landscapes.
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Q. Is black plastic or landscape fabric a good mulch?

A. Black plastic can be used to heat up an area (such as for sweet potatoes or pumpkins), and as part of the weed-control regimen, but should not be left in place as it prevents moisture from entering the soil and otherwise interferes with soil health. Roll or fold it and reuse the plastic year after year (I use 5 mil or 6 mil sheeting, not flimsy one-use plastic).

Suppressing weeds with black plastic is called tarping, technically; using clear plastic is called solarizing. Those useful tactics are explained by a University of Maine researcher in this interview.

Landscape fabric, or so-called geotextiles, are not a substitute for mulch. They should not be used in garden beds, though they may have a role as a weed-block beneath gravel of pathways or patios, for instance, or on the floor of a greenhouse.
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Q. What about Ruth Stout’s mulch methods?

A. Long before phrases like “lasagna garden” were making the rounds of the as-yet-uninvented internet, Ruth Stout (author of “Gardening Without Work,” 1961) was layering all her organic materials on top of her soil—sheet composting, as it might be traditionally called. Her tactic served to thwart weeds, reduce the need for fertilizers, conserve moisture and spare her the work of composting in a conventional heap with all the toting and turning of materials.

Her approach to gardening starts with the foundational principle of applying mulch, mulch and more mulch, and then simply moving it back a tiny bit each year a bit to make room for a row of seeds rather than all that turning and tilling (and weeding).

She said the “aha” came one spring when the plow man hadn’t come yet to till, and she was eager to get planting. She saw that the asparagus (a long-lived perennial vegetable crop) was already up and growing, right through the layers of fallen leaves and such. “I walked over and said to the asparagus, ‘We don’t have to plow for you; why do we have to plow for the other vegetables?’” Stout recalls. “And the asparagus said, “You don’t.’”

Where do you get all that mulch? The garden creates it, or at least some of the raw material that becomes it: spent cornstalks and uprooted pea vines and the like, to which Stout added fall leaves and also bought-in straw or hay (“spoiled” hay was fine, and cheaper; don’t worry about a little decay, she said).

More on Ruth Stout’s methods (plus video of her) is in this post.
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Q. Do you mulch your pots and other containers?

A. I do apply mulch to the soil surface in my containers, to help keep roots cool and keep moisture in. Depending on the plant, I may use composted stable bedding or a small stone (pea stone).

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    1. margaret says:

      Hi, Gabriela. Love mulch — but not when it tries to show off! I used dark-brown, not-too-coarse textured material that feeds the soil as it breaks down further and keeps moisture in and weeds down a bit, too. It’s not something that’s supposed to attract your eye, but to enrich the soil and otherwise serve to make a healthier garden.

  1. Eileen says:

    Great article on mulching. There was a period some years ago when certain garden people were saying you did not have to mulch if plants were grown close enough. I never did believe this and continued to mulch. I use shredded spaghnum moss on my vegetable bed, looks good and adds to the soil. I have a small raised bed so it is not that expensive to do.

    I moss all of my baskets and containers with oregon moss that I order, decorative and keeps them moist.

    Eileen

    1. margaret says:

      Thanks, Eileen (and hello!). I love mulch, and think of it as my best soil-building tool. Hope to see you again soon.

  2. Bonita says:

    We’ve had a country garden for a dozen years in a valley that was impenetrable with brambles, thistles, and willows. It was plowed once by a neighbor then we fought with difficult heavy clay clumps that created low yields of veggies, high yields of weeds. We read Ruth Stout and started adding sheet compost of leaves,wood chips, grass clippings, hay, and cardboard and news paper, seeing some improvement the first few years. Then we began keeping a flock of a dozen or two laying hens. The straw or hay bedding mixed and fertilized by the chickens, composted in a heap for six months and then added to the vegie garden has worked wonders. We now have excellent tilth, balanced fertile soil that tests very well for nutrients and minerals. Somewhere I learned that adding the wood ashes from our stove would discourage slugs. Our neighbors are overrun with them, but we haven’t had a problem. Any gardener that can keep some chickens can have a great mulch source and be one step closer to permaculture, cuz the chickens eat most everything from the garden that we offer them.

    1. margaret says:

      I am so jealous, Bonita. Want chickens like crazy, but so many wild animals in this rural area, it’s really a challenge to keep everyone out of a henhouse. Most people end up with total bloodbaths here (weasels, fishers, coyotes, raccoons, fox, you name it). I keep almost building a coop and trying anyhow! :)

  3. Bonita says:

    After hearing horror stories of chicken massacres from neighbors, I built a fortress for our chicks. I laid down chain link fencing ( scrounged from someone’s trash) so nothing can dig in. I built a sturdy building from recycled lumber ,windows, doors , and metal roofing. then added hardware cloth covering windows openings for safe venting. I latch the doors with padlocks at night, cuz raccoons are so clever with latches and hooks. I added an outdoor porch with more fencing for floor and sides plus metal roofing. We feed organic grain and throw kitchen and garden scraps in the outer yard which they compost for us. Third, I fenced a quarter acre of wooded area for their daytime pasture. Heirloom chickens seem very smart about hiding from the hawks. So far we have had good luck avoiding losses to predators. The girls are such joy and our friends who buy eggs @ 4$ /dz say they are the best they’ve ever tasted. I strongly recommend preemptive design and build to avoid the heartbreak of predators. Also introduce Jack so they become companions. Our cat Rover is a good mouser by the coop. Go for it and evangelize for more backyard flocks. Great fun, safe nutrious eggs, and terrific fertilizer for gardens.

  4. robert a says:

    One exception to your caution against using sawdust as a mulch: it’s great on the paths between the raised beds in my vegetable garden. Weathers to a nice dull color, feels great on bare feet, and cheap by the pickup load at my local sawmill. And perhaps because it’s mostly from pine and fir (resins?) it seems to really suppress weed germination.

    1. margaret says:

      Hi, Robert A. Yes, I use wood products in the pathways, too (more bark chips or shredded bark than sawdust, but same idea). I just don’t use uncomposted wood products of a coarse texture in growing beds around plants. Agree. Nice to see you.

  5. Tim H says:

    Hi Margaret,

    Although not previously an avid gardener, I bought a house with an incredible flower garden (several thousand dollars worth at least). I have Lilly flowers and Bee’s Balm, Coneflowers, and too many other flowers to name. I want to take care of this garden, in the MLS pictures I saw some cedar (I think) mulch. However, I do not know much about mulching until now (reading the article above, thank you!). I am worried if I mulch next spring, that some of the bulbs will not push through. is this a valid fear or am I WAY off base? I don’t want to do damage to what is already in place.

    1. margaret says:

      Hi, Tim. A good mulch (not too coarse!) applied to a depth of like 2 inches or thereabouts, not piles and piles, won’t give you any troubles. There are a few plants (peonies, for instance) that don’t like to be too far below the soil surface, but those are a real minority. Definitely keep in mind getting some good mulch that has been aged/composted first if you can.

  6. Dahlink says:

    I love all the points of view here, but count me among those who don’t love mulch. I do adore compost, and top-dress my beds at least twice a year. I also use small stones to “mulch” some of my herbs in pots (the lavender particularly seems to appreciate this). But my goal is to achieve a perfect tapestry of ground covers so that I never need to mulch again. I am getting there, little by little.

    My mother-in-law saved peach pits to use as mulch. Am I alone in not finding that either useful or attractive?

  7. Sharon says:

    I am reluctantly using mulch until my gardens fill in and the plants themselves provide most of the weed-preventative shade and I will then only need to top dress with compost soil-crust prevention.

  8. Lesley says:

    Do you have any mulch recommendations when artillery fungus is a problem? We were told to ‘mulch’ with stones but I really don’t like the look of that but I also am not fond of little spots all over my house.

    1. margaret says:

      Hi Lesley. I don’t know much about it so I just read this Penn State University Frequently Asked Questions page, and this pdf from Cornell. I am OBSESSIVE about using only mulch that has been well-aged by composting BEFORE it arrives at my site, which is said in both documents to reduce the issue. I don’t bring any wood chips/shavings/other products into the garden that are not composted thoroughly first for this and many other reasons.

  9. Angela L. says:

    I like to mulch with the neighbor’s leaves that they conveniently collect, bag, and place at the end of their driveway for me to pick up. (How handy!) Well, they don’t realize it, but I still thank them for their services. Anyway, I have fungal issues in my vegetable garden every year, and I can’t “move” my garden as is normally recommended because I live in a neighborhood full of tall trees with only one sunny spot in my back yard. I am concerned that by using my neighbor’s leaves I may be introducing more “contaminants” to my garden such as fungal disease spores, but aren’t these things floating around in the air in our neighborhood anyways? I was wondering if leaving them inside their black plastic bags for a while would help kill off some of the fungal visitors (it’s pretty hot in East Texas, even in the fall). Any thoughts on the pros and cons of neighbor’s leaves as mulch?

    1. Margaret Alvarez says:

      Hi Angela, I’m reading your post in April 2014 so you may have figured this out by now, but
      when you think about how to amend the soil for different plants, remember that it’s the webs of mycorrhizae in the soil which enable plant roots to take in the nutrients they need to thrive.
      A lot of my own mulching questions have been answered by the book _Teaming With Microbes: A Gardener’s Guide to the Soil Food Web_ by Lowenfels and Lewis. In a scientific but very friendly way, they walk us through why we should care about the microbes in our garden soil, and which kinds of plants need which kinds of nutrients to best feed the mycorrhizae their roots depend upon.

      I had many “Aha” moments while reading this book, and recommend it to anyone who mulches. We can help our veggies, and our woody shrubs (here’s where you’ll want to use those wonderful leaves!) — but not with the same materials, because their roots depend on different kinds of microbes in the soil.
      Good luck!
      :)
      –Margaret

  10. Carolyn says:

    Just like Angela above, I am wondering how you know if your compost is contaminated? Anything with livestock manure could have residual herbicides in it that would actually harm plants (the hay the animals consumed could have been sprayed ) and I have read that piling it up or composting it actually makes the herbicide take longer to degrade.

  11. Carolyn says:

    Just like Angela above, I am wondering how you know if your compost or mulch is contaminated? Anything with livestock manure could have residual herbicides in it that would actually harm plants (the hay the animals consumed could have been sprayed ) and I have read that piling it up or composting it actually makes the herbicide take longer to degrade.

  12. jmack says:

    I have a gardening neighbor who uses sweet peat to mulch. I’m not even sure what it is but I understand it’s a non-renewable source which, for me, would also make it a no-no. Any comments?

  13. Kris Ra says:

    My neighbor’s tree drops alot of pine needles in my back yard. Are pine needles good mulch for vegetables? Does it add too much acidity to the soil for other plants, such as fruit trees? In the edible-free front yard, I’ve been pulling the weeds but they are overtaking my garden. I would hate to resort to chemicals but they are becoming more appealing for the ease of use and because I have a large space to cover. Please advise!

  14. Judith says:

    Hello Margaret, please may I enter the discussion. I really enjoy the comments and continue to learn from all. I have a large garden and mulch continually. Before laying down the mulch each year I water and then fling ! handfuls of blood and bone over the area, then lay down the mulch.Usually Lucerne hay, stable straw or shredded bark, never, never the dyed stuff.
    I like to ruffle up the mulch a little bit in areas were it is possible, think it allows the air into the layers and keeps the soil fresher, do you think this is a good idea?
    I do use newspaper in areas that are not too visible, but find it takes a long time to break down, is there anything I could put with it to speed up the process?

    1. margaret says:

      Hi, Judith. I like to fluff up the mulch if it’s sort of matted down in some spots, and I top it up with fresh as needed. As for the newspaper, besides moistening it with the hose thoroughly after applying, before topping with mulch, I don’t know.

  15. Mary Jane says:

    URGH! I just bought and put down cedar bark mulch (recycling the plastic bags).
    However, I “broadcast” in fairly lightly so I can hand-mix some peat moss with it. Does this redeem the bark a bit?
    I also use pebbles in service areas of the garden (like hose area) to hold soil, and to create low-labor pathways.
    Thanks, as ever.

  16. Mary Jane says:

    P.S. Related to Jack! he looks great on the colorful circle patterned rug.
    Maybe a jacket in that rather than a classic tux? Like Lionel H. might have worn playing the xylophone?

  17. Daniel says:

    When two large douglas firs were taken down, the limbs were chipped. The pile sat for about three months, about 8 feet deep, occasionally watered, but the Hood River Oregon heat dried it out. No nitrogen was added. That chipped (limbs, bark, needles) mulch has been spread 3-5 inches deep over an area that we are now, 5 months later, getting read to plant. Given your comments about un-composted mulch, what would you recommend? Scrape it all up (100 x 30 feet), about 6 -8 cubic yards (yikes!), or can we top it off with a nitrogen fertilizer? Chicken manure? (My wife sent me your article, with an ‘I told you not to do that’ admonishment. Thanks

    1. margaret says:

      I don’t use wood chips or other coarse wood products on my beds for vegetables or flowers, Daniel — only on pathways. Frankly, I don’t even use them on my beds if they are well-aged — wood just doesn’t “feed the soil” by breaking down gradually in place the way I insist a mulch does. Wood shavings that animals (cows, horses) have used as stable bedding, that then has been composted thoroughly (turned regularly, etc.) yes, but not chips/chunks.

  18. Russ says:

    I have used grass clippings this year, gathered with my bagger on my lawnmower. I have mulched rows of bush beans with the grass clippings, and it has worked wonderfully well. I’ve had almost no broad leafed weeds coming through the mulch, but just a few that I could carefully remove and pullout sticking through the mulch. Some types of grasses have poked through the mulch moderately in some areas of the bean patch. However this year was the first year I have used this piece of ground and it was previously growing in grass. Next year I think I will have killed most of the rest of the remaining grasses that had grown on this ground when I roto-till the ground in the fall, and then again next spring a couple of times before I plant next years garden.

  19. Eliza J says:

    Hi Margaret…. Love this post! We have been very frustrated with the weeds in our garden and keep hearing how mulch helps. We use leaves with household and garden veggie material to make compost. Mulch ~ has just plain confused me. We were planning on trying newspaper this year to help keep the weeds down, but then have to figure out what to cover it with. We have a 75′ x 20′ garden that is about 6 years old. This is on the outskirts of an old pasture so there are lots of weeds around. We have no shortage of leaves and are planning on getting a leaf shredder this Spring. Thank you for all the wonderful information on mulch. I have printed this off and will be reading and re-reading this along with my husband. Happy gardening!

  20. John says:

    We have mulch from the city. We can pick it up. Theres fresh and old decomposed mulch very dark almost totally decomposed. I have been picking this up, because i think id the best for my fruit trees, bluberries, raspberries and also vegetable garden and flower garden. Is this correct? Do you think the older is better? And can i use it everywhere, do i need to feed some help with Nitrogenio? Orbecause is decomposed should be fine? Should i get the oldestmulch as possible or the fresh?
    Many thanks

    1. margaret says:

      Hi, John. Aged is always better, but what age exactly has the best composition and fertility would be impossible to know without testing it. You don’t say what the mulch is made of — wood chips, or compost from vegetables and other plants (leaves etc.) or what?

  21. bluespinningplanet says:

    Great article on mulch and I love that you mentioned that, when you buy it, you get stuff that isn’t bagged. As gardeners, caring for the earth is foremost and plastic just isn’t environmentally sound. Neither, actually, are those dyed mulches. Going one step further, I will say that I’ve never, ever in my life bought mulch. My mother taught me that it’s everywhere and it turns out she was right. I gather seaweed at the shore, pick up manure from local horses, keep every leaf that falls on my own property and pick up bags of them put out for pick-up day, help myself to wood chipped branches the town offers, grab Halloween straw bales when neighbors are done with them, etc. etc. I have incredible soil and I credit it all to mulch.

  22. bluespinningplanet says:

    Great article on mulch and I love that you mentioned that, when you buy it, you get stuff that isn’t bagged. As gardeners, caring for the earth is foremost and plastic just isn’t environmentally sound. Neither, actually, are those dyed mulches. Going one step further, I will say that I’ve never, ever in my life bought mulch. My mother taught me that it’s everywhere and it turns out she was right. I gather seaweed at the shore, pick up manure from local horses, keep every leaf that falls on my own property and pick up bags of them put out for pick-up day, help myself to wood chipped branches the town offers, grab Halloween straw bales when neighbors are done with them, etc. etc. Some goes right on the garden beds; some sits in a compost pile for a while first. I have incredible soil and I credit it all to mulch. With years of mulch, I could actually plant daffodil bulbs with my bare hands; no trowel needed!

    1. margaret says:

      People who come to my workshops here are shocked when I dig my hand into the beds to move something. So I agree: nothing like regular additions of organic matter to make the soil so welcoming.

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