Wonderful wood chips

I’m in love…with arborist wood chips.  These are not your beauty barks or other packaged mulches, but the chipped branches and leaves fresh from the tree crews. It’s a great way to keep this resource out of the landfill – and don’t even get me started about using this great mulch material for a “biofuel!”

I’ve written about wood chip mulches a lot, but thought today I would post some photos to show you how well they work in suppressing weeds and promoting growth in restoration sites.  We published a paper on this in 2005, though we’ve been using them in ornamental and restoration landscapes for about 10 years.

Here’s a recent project: a wetland buffer enhancement was being installed in an area that was covered in Scot’s broom (Cytisus scoparius) and blackberry (Rubus discolor):

Heron's Glen-6

We had a brush cutter mow it to the ground, then put a foot of wood chips down.  Later, we planted poplar, ash, willow and alder on the site:

We had to keep records, both written and photographic, for the county who monitors wetland projects.  So we took photos every year at the same points for comparative purposes.  Here’s what part of the site looked like immediately after planting and then after 5 years:

That’s not to say that we haven’t had to battle resurgent blackberries.  They migrate over from the wetland itself (which we can’t touch) and tip root.  But the increasing shade and competition from the trees has weakened their ability to take over, and the Scot’s broom has been gone for years.

So that’s one reason I love wood chips.  I’ll do a follow up some week showing how they can be used in the home landscape.

Published by

Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors "The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors Books: http://www.sustainablelandscapesandgardens.com

49 thoughts on “Wonderful wood chips”

  1. Nope! You can, of course, but you don't need to. Plus, it smells great when it's fresh. No issues about either disease or nitrogen deficiencies (I can send links to those materials if you want them).

  2. I've used fresh wood chips for my ornamental garden in the past because I was too cheap to buy mulch. The only issue I had is that it breaks down more quickly than bark mulches, so it must be replenished more often.

  3. Cheap is good! And you're right, Dave, they do break down faster. At home, I generally put down about 6 inches in the spring. It settles pretty quickly to about 4 inches. In general, that lasts until the following spring.

  4. i remember clearing glossy buckthorn patches back when i worked for a park district in the midwest. we would then use these chips in our parks. quite a few weed seeds in that stuff! i guess its a trade-off for the cheapness.

  5. You're right, JD, the quality of the chips can be variable depending on the source. I try to avoid loads that have English ivy, poplar and willow in them as younger stems can easily reroot. Cheap is good as long as it doesn't add to your labor costs with increased weeding!

  6. Nothing makes me happier than a load of woodchips gently steaming in the driveway. I view arborists chips as instant duff. What could be better for woodland plants like rhodies?

    Breaking down is not a bad thing. It enriches the soil. Bark, being suberized, never really breaks down to enrich the soil. My soil is sandy. It needs all the organic matter it can get.

    I guess the fact that it takes me a few days to spread the chips is a good thing. The pile heats up to 130 degrees, and kills seeds and twigs.

  7. Wow, Deirdre, you sound like my clone! I too have a steaming pile of chips in the driveway every spring. Since I prefer conifer chips, it smells like Christmas. And it keeps your hands warm on cold spring days!

  8. I recently removed 50 year old junipers from a steep hillside. Want to mulch before planting. Will arborist chips work or will they slide down the hill? As an alternative I can get "compost" from the landfill. It has a high content of shredded brush, leaves, and grass, but hasn't really been composted yet. The particles would be finer in the "compost". Suggestions? Thank you!

  9. Phyllis, you can use them on slopes. What we've done is a couple of things: 1) lay down coir cloth (like burlap, kind of) over the top to keep them in place or 2) create deadfall terraces along the slope to keep the chips back. You can do this easily with large branches/small tree trunks, held on the slope by two wooden stakes on either end on the downhill side of the timber. <br><br>
    You can also use the other compost-type material, but you can't lay it on thickly. It tends to reduce water and air movement, given its finer texture.

    1. Hi—we recently moved to a house in northern NJ, and our backyard is a steep slope down to a small river. We love the view but along the switchback path to the river are wedges of completely overgrown, tangled and prickly brush, which we’d love to make a bit more attractive and safer for our 2 kids. We’re wondering about covering it now (before it grows up again in the spring) with a thick layer of wood chips which is infinitely less expensive and more environmentally sound seeming than most of the options landscapers have presented us with. Our worries are that we have read that it can harbor bugs and termites and lead to significant problems, and that it will all just slip right down the slope. Do you have any insights on this? Thanks so much for your help!!!!

  10. I have enjoyed reading the information about wood chipping. Really, entire discussion is more helpful and all the tips are more effective too. I am very glad to go through this kind of helpful article. Thanks for sharing a nice article.

  11. My husband and I learned about the value of wood chip through your Great Courses lectures. We live in north Florida. Is pine mulch a suitable option please? Many thanks!

  12. I am a hobby wood worker and have raised bed vegetable garden. Today Dec 31, I planed some alder and now have a large bag of wood chips. Rather than add these to my garbage, I have several alternative uses possible. Which if any would you recommend? 1. Add as a ground cover around various pants around the house (rhododendron, barberry, small evergreens; 2. Mix these chips in with my raised bed soil? Is yes, should I do it now or when I add a processed manure in the spring with mushroom mulch? 3. We have recently added fresh topsoil ( acidic) behind a new concrete terrace wall. The plan is to plant some arborvitae in the spring. Is there any benefit to mixing some of the alder chips be in with that soil?
    Thanks in advance.

    ORGramps (Rex)

    1. Hi Rex –

      Sorry for my late reply – COVID19 has just escalated my email and online work load! Anyway, do NOT mix your chips into the soil, but yes, do use it as part of a mulch layer. It will be rather inert, since this is processed lumber, but may adding some shredded leaves or even a little manure that will improve its functionality.

  13. Since I became aware of your advice on using arborist chip mulch a few years ago, I was thrilled to get some from a friend who had a couple of trees taken down. Since there were also a lot of large-ish bark pieces lying about, I brought them as well, and covered my garden path. The wood chip mulch has been a total success (thanks!) but I wonder if you would not have approved of using the bark in the path? btw, I am committed to doing the right thing, and am grateful to you and your fellow professor-experts to steer me in the right direction.

  14. This is a great article, thank you! I was just hoping for a tiny bit of enlightenment since I am a total novice. We have a secondary lot dominated by six 50 ft tall cypress (?) trees that have very aggressive roots and need to go. If I can convince the arborist to leave the chippings, can I spread them and smother the grass below? And if I wait a season or a year, will I be able to plant underneath the chips? I would love to have a blank slate for experimenting (though the poor innocent plants I bring back from nurseries may not agree!)

    Thank you again!

    1. Yes, you should absolutely keep the chips. Thick layers will block sunlight to kill the weeds (“smothering” is not a good term to use, as we are not excluding oxygen). But mow the grass first, so it’s very flat. You should be able to move the chips aside after several months to plant. Keep them to cover bare soil once you are done. Good luck!

  15. Hi Linda, I used to use a layer of newspaper underneath arborist wood chips and you’ve convinced me to omit that layer with very sound reasoning – Thank you! We’re working on a public space that will get little maintenance for liability reasons and I wonder if you can tell me if native wildflower seeds will germinate in the wood chip layer. It’s 9/1 now and we could apply wood chips this Fall. Seeding could be immediately, later in the Fall, or in the Spring, however the milkweed and goldenrod seeds (our two most important seeds) need stratification. Would love to see bloom in the Spring. Any insight and advice would be appreciated!

    1. Glad you are open to changing your practice to benefit the soil!
      The drawbacks to wood chip mulches is that NO seeds will germinate in them, including your desirables. I still recommend deep chip application in the fall. In the spring, you can pull back the mulch from the areas you want to seed. Just put your seeds in the refrigerator for winter and then they will be ready to go in the spring. You will need to watch for weed seedlings, as the seed bank in the soil will be full of them. Once your desireable species have taken over you can replace some of the mulch, or just hope that the wildflowers will outcompete the weeds. Good luck!

      1. Dr. Chalker-Scott,

        When you say “pull back the mulch…” is that 100% of it, or would it be good to leave some so the ground isn’t just bare soil? But thin enough to let light through to the seeds for germination? I’m afraid of erosion and seeds floating away (norther Virginia — springs can be rainy). Thank you.

  16. Definitely converts to wood chip mulch on the garden for many years now, but a few questions over potential incompatability of wood chip mulch and ground nesting bees? Also wood chips in our garden provide a ‘worm buffet’ in the soil, which attracts wildlife such as skunks and raccoons that relentlessly damage plants over summer and fall. What to do? Your comments very much appreciated. Thank you again.

    1. Dixie, what I do is leave space under my low shrubs and perennials unmulched. It’s not needed for weed control, and that way ground bees and other insects have a protected area for nesting.
      In terms of your healthy soil and its worms, the downside is wildlife damage. Where you can, use fencing to keep critters out (like the fencing I’ve used around my raised beds) https://gardenprofessors.com/why-soil-tests-matter-lessons-from-my-vegetable-garden/.

  17. Dr. Chalker-Scott,

    Thanks for all your wisdom on wood chips (and so many other topics). Question: how long should I leave the wood chips in place? I’ve seen some folks talk about “years” but elsewhere you’ve said “months” — how many? I’m sure it depends on time of year, location, etc.; I’m in Falls Church, (northern) Virginia and just (12 Feb) put down five yards of chips 12″ deep where I’m reducing our lawn to make way for native shrubs, trees, perrenials, and ground cover. When can I start planting? Native nurseries open next month…I’m impatient!


      1. Thank you. I’ve noticed that the second batch of chips (pine) seem to be “hotter” than the first (ash). The pine was hot and turning gray after sitting for one week in my driveway!

  18. I recently planted some very small tree seedlings – caliper less than my finger width. Now I want to use arborist chips to suppress the weeds that are growing up around them. I am worried that the decomposing chips will take so much nitrogen out of the soil that the seedlings will suffer. What would you advise?

  19. I am wondering about the mushrooms that often grow in wood chips. I had a tree company dump wood chips behind my house and it was more than I could use right away so most of it sat there a long time. Several different mushrooms appeared which I generally think of as a good thing. However one kind looked like it might possibly be deadly amanita. I am now wondering if there might be a potential problem using wood chips full of amanita mycelia on lettuces, herbs, carrots, etc.

    1. Correct ID is your first task.
      Amanita is toxic only when ingested. Manual removal of any volunteers is easily done once you know what you’re seeing.

  20. I spent the day, hauling apple tree branches on to my property from the adjacent neighbor’s orchard (which would otherwise have been burned) because I became a true believer in arborist chips after seeing an interview with you. Now I have a mountain of branches and no way to chip. Do chippers have settings that make them come out the optimum size? I guess I’m willing to invest in a chipper but I’d prefer a service. I’m in Oroville, WA and planning to create a hedge row, having just read the book, Nature’s Best Hope. Advice please.

    1. Chipper adjustment depends on the make of chipper.
      As far as chip size goes, the coarser the better. Avoid fine or small pieces, they can pack and interfere with water infiltration.

  21. I watched with great interest your YouTube video about using arborist wood chips as a mulch. I have very dense clay soil and parts of my front garden bed are infested with pernicious weeds (particularly, a miniature morning glory-type vine that strangles even well-established plants). I’m getting older and no longer able to keep up with the weeds, and it’s difficult to find people willing to hand-weed (vs. Roundup). Rather than resorting to an herbicide, I plan to put down 12 inches of arborist wood chips as a weed suppressant and (eventually, I hope) a soil enrichment, and then continue refreshing the wood chips at the surface to maintain a 6-inch depth.

    I received an order of arborist wood chips from Chip Drop, but there doesn’t seem to be any organic matter like leaves or pine needles among these chips. Can I use the chips as they are, for initial weed suppression, and then add a layer of bio matter in a few months (maybe shredded leaves or biochar or manure that I would purchase) before refreshing the woodchip mulch in the Fall? If so, what would be the best type of organic material to add to the wood chip mulch for shrubs and perennials?

    1. Any chips, with or without leaves, will work! You don’t need to add anything else unless you have had a soil test showing that you have a nutrient deficiency. The wood chips provide a low, slow feed of nutrients, which slowly builds soil. You’ll never need to add anything else.

  22. Articles in some of the gardening magazines I read say densely growing flowering plants that act as living ground cover are preferable to wood chip mulch because plants are more beneficial to pollinators. What is your opinion? And, what ground cover plants would you recommend that both attract pollinators and suppress weeds?

    1. Ground covers do not provide the substrate for mycorrhizae that most plants need for optimal growth – pollinators are not the only thing important in landscapes. They also compete for water and nutrients. Personally, I use a mixture of groundcovers, hardscape (walkways) and arborist chips. Which groundcovers work best will depend on your location – take a walk around your neighborhoods and see what looks good and works well.

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