mulch faq’s

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 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 cake and fail to decompose.

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. Wood products in particular may also rob soil Nitrogen while decomposing, unless composted first (before they’re spread as mulch).

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.
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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. 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.

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 use straw (which is of course not dark-colored), preferably chopped. 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.

For more details about pros and cons of different mulches, try the Cornell Cooperative Extension mulch website.
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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 in the ground, 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 them 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 seems 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!).

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) 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.

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.
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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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66 comments
March 16, 2010

comments

    • 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. 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

  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.

    • 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.

    • 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.

    • 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.

    • 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?

  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. Lesley says

    interesting about sweet peat b/c I hd a few Master Gardeners tell me that was the best kind of mulch to buy.

  14. 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!

  15. 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?

    • 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.

  16. 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.

  17. 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?

  18. 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

    • 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.

  19. 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.

  20. 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!

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