Growing Greener Podcast – Wood Chips with Brian Vagg

How to Make Wood Chips a Basis for Soil Health

Brian Vagg of the Compost Academy discusses how wood chips, if properly managed, can be a cheap and reliable means for supplying the organic matter—and microbes—that most garden soils are lacking. Listen and read the transcript.

September 9, 2026

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Transcript

Growing Greener host Tom Christopher

Welcome to Growing Greener, your guide to environmentally informed gardening. Produced in partnership with the Perfect Earth Project, this program brings you each week some expert who puts you in touch with a different aspect of gardening in partnership with nature. Our goal is to make your personal landscape healthier, more beautiful, more sustainable, and more fun.

This is your host Tom Christopher, and today I will be talking to Brian Fagg, one of the founders of Compost Academy and a soil health consultant, about the use of arborist wood chips as an amendment for your garden soil. There are very few bargains left in the gardening world, but wood chips, which typically may be had for free and delivered to your site, definitely qualify as that, as long as you apply them correctly. Before we go to the conversation, though, I want to thank Growing Greener’s sponsor, the Garden Conservancy, a national nonprofit dedicated to preserving, sharing, and celebrating America’s gardens and diverse gardening traditions. Through preservation, education, and public access, the Conservancy helps protect these living works of art for future generations. Learn more and discover gardens near you at GardenConservancy.org.

Welcome to Growing Greener, Brian.

Brian Vagg

Thank you. Thanks for having me.

Tom Christopher

Brian, it’s said in your online bio that you have a scientific background. Can you clarify?

Brian Vagg

Sure. Well, my scientific background comes from the high-tech industry. My formal college education was in information systems management, so I worked on large-scale compute systems. I kind of finished my career in the high-tech world working on large supercomputers.

It’s interesting because that doesn’t seem on the surface to translate very well into understanding growing systems and ecology and those kind of things, but there actually is some kind of transference there. In those large compute systems, there’s a lot of complex interactions that have to occur. You have to kind of understand how the system works and how it flows.

It’s the same thing when I look at ecology and plant ecosystems. Understanding those complex interactions is extraordinarily important. I think my education in the high-tech industry has translated very well, actually, into understanding how plant systems work.

Tom Christopher

Well, that is very interesting. Did that play a role in attracting you to Dr. Elaine Ingham’s teachings about the role of the life in the soil, all the microorganisms, bacteria, and fungi, and the part they play in creating a fertile soil for plants?

Brian Vagg

For sure it did. I think taking what Dr. Elaine really kind of spoke about, I think I took to it like a duck to water in that sense because she really gets into a lot of the nuance and the science behind it. For me, I fall right into that, so that definitely helped. But really how I came about all this is my wife and I had a homestead in Northern California. We were really trying to grow our own food and really establish good plant systems, but my experience from my childhood was very conventional, so using rototillers and applying fertilizer and whatever “-cide”, like a fungicide, pesticide, whatever, to deal with whatever problems you have.

Really, after a number of years trying to run our homestead that way, it just became problematic. Plants formed less, I had to put more inputs on, and I was really just struggling with putting chemicals in the ground or on the plants I’m eating. In fact, I remember distinctly one day I had a pest problem and I was looking at this material that I was going to put on my plants. I’m reading all the warnings. This is dangerous. Go seek immediate medical attention if you spill this on you. I’m like, why am I putting this on my food? There’s got to be a better way. I really came about it first through permaculture. I started looking at permaculture systems and that kind of interaction. It wasn’t until I read a book by Jeff Lowenfels, Teaming with Microbes, and Dr. Elaine Ingham wrote the foreword to that. I went, oh my gosh, so many dots just got connected in my brain. I went out and I looked online, found a bunch of YouTube videos, and then I just said, okay, I need to know more. This is really something I can dive into. Our passion around these growing systems really started there.

Then from that, I had to make a decision somewhere in my career. I said, you know what? I don’t want to be doing the high-tech industry anymore. I think I want to help people understand how to grow things and understand these biological systems and how they work. That’s where it’s led me today.

Tom Christopher

You’re the co-founder of Compost Academy. What is that?

Brian Vagg

Compost Academy is an online education school where we really try to teach the practices of regenerative agriculture, horticulture, with a focus on understanding the role of microbiology and soil ecology. Really, our goal here is to help teach practitioners. This is from a small scale, so the homeowner or homesteader, all the way up to large-scale agriculture or horticulture. Really, these principles apply in any growing system. We do have students that really stretch that gambit from very small scale to very, very large scale.

Tom Christopher

Well, let’s move on to wood chips, which is my present preoccupation. My experience as a gardener has been that almost every soil I’ve ever worked with, and I’ve gardened a lot in different places in the Northeast and also in Central Texas. And all these soils I worked with shared a common problem from a gardener’s perspective. They were all low in organic matter. Maybe that’s because I’ve always gardened on sites that had a history of use by humans, such as residential areas of long-settled towns or former agricultural fields, where I’m speculating now, but maybe human mismanagement had depleted the soil. Is that something you’ve also noticed is a problem?

Brian Vagg

For sure. Low organic matter in soils, usually caused by heavy disturbance or heavy use, is a very common problem. And we see that in both agriculture, where a lot of agricultural systems are run in such a way that the organic matter depletes over time. Like you said, in residential systems, I’ve been in plenty of situations where they’ll go in and remove all the topsoil, and they’ll grade out the land, and pretty soon you’re left with a subsoil that doesn’t have a lot of organic matter, and then people are struggling to grow. And for me, wood chips are just one of the most essential tools to be able to incorporate that organic matter back into the soil. Now, it’s not without problems or troubles. I mean, people have definitely documented and showed, hey, I added wood chips to my growing situation, and my plants performed horribly, or they turned yellow, or they seem to be lacking in nutrients.

So it’s really about understanding how the wood chips are going to behave, and what types of wood chips you’re working with becomes extraordinarily important. Knowledge, in this case, is really going to arm you to deal with the nuances that exist, and be able to use wood chips as a really effective tool.

Tom Christopher

Yeah, because I’ve tried a lot of different materials for increasing the organic content of my garden soils. Years ago, we used sphagnum peat, before we knew how environmentally harmful the strip mining of peat bogs is. I’ve used manure, a good deal of animal manures, from stables and farms, and even for a while from the Bronx Zoo in New York. I’ve used spent growing media from mushroom farms, too. And all of these things had their problems, and securing them in bulk involved considerable expense and or lots of work in picking them up. And this is one of the reasons why I’ve become so enthusiastic about wood chips, because arborists will typically deliver them for free to your driveway. And if they come from tree prunings or tree takedowns, they’re about as free from contamination, I think, as anything you’ll find.

Brian Vagg

I agree with you. I have the same feelings that you have, which is, I always try to look for what local sources do I have versus anything that I have to bring in. One, there’s a cost almost always associated with that, just a financial cost. But then you talked about peat, you know, there’s also an environmental cost that you want to try to avoid. And so looking for sources that are local and also sources that are renewable, like wood chips is an example.

For arborists, it is a waste product. If they don’t drop off their wood chips, they have to go drop it off at a composting facility and they have to go pay a tipping fee. So, it is a cost to the arborist. So, having a system where you’re able to take somebody else’s waste stream, utilize that waste stream, it’s really a win for everybody.

The arborists don’t have to transport those materials, which consumes gas and all these other things that potentially have environmental costs. So, I think looking for those sources to improve our growing systems that we can really take on locally is a fantastic way of going about it. And I think wood chips in particular, once you get that chip drop from an arborist, just really thinking about how you want to use it really dictates how I’m going to start my process here, which is, am I going to age these wood chips or am I going to use these wood chips as fresh? Just having some of that basic knowledge then really helps you deal with those products effectively and not introduce problems.

If I take a fresh wood chip and I decide I’m going to till it into my soil, I’m probably going to run into problems. But if I let that wood chip age for six months to a year and then incorporate it into a soil or soil blend, it behaves much, much differently.

Tom Christopher

Yeah, I read that in a brief article about the use of wood chips that Compost Academy sent around by email. And I was very interested by that, partly because if you read almost anything, and I would exclude your article from that, almost anything about using wood chips in the garden, you’re going to run up against the same warning. Wood chips, the writers are going to say, will tie up the nitrogen in your soil. And nitrogen is the nutrient that plants use in the greatest quantity. So, wood chips are going to cause your plants to, as you say, go chlorotic, turn yellow and produce only weak growth. That’s according to your article, which I found very interesting, just not true.

Brian Vagg

Yeah, well, there is a truism in there. You know, with the previous article, you cited, you know, a body of work sites that wood chips tie up nitrogen. And really, there’s more to it. It’s not necessarily the wood chips that are tying up or what we call immobilizing the nitrogen. It’s the microbes, the decomposers that are going to bind up and tie up that nitrogen, because they need nitrogen to create amino acids and enzymes and all those wonderful compounds that they use to break down the wood chips, to do their role of decomposing.

So, yes, when you put wood chips down, either in the soil on top of soil, there’s going to be some amount of nitrogen immobilization. What we want, though, is we want nitrogen mineralization, which means it’s going to release it back into the soil in the form that the plants can then consume as food or nutrients to be able to support their growth.

This is where understanding the role of soil ecology in the soil biology is extraordinarily important. If you have bacteria and fungi, which are usually always early colonizers of any kind of ecosystem, they’re going to start doing their work. They’re going to try to find whatever sources of nitrogen they can to be able to create those amino acids and enzymes and start the decomposition work.

But the problem that we run into is it will start pulling all the soluble nitrogen out of the soil. And that’s where people see those problems. But by having now a functioning soil food web where we’re going to put in protozoa and nematodes and micro arthropods and all these other predators, it’s the eating, the predation of the bacteria and fungi that is going to release the nitrogen back into the soil.

So there is this balance. So if you’re in a situation where you’re going to take fresh wood chip and you’re going to put it into a very poor soil, and I mean by poor, it doesn’t have structure. It’s microbially poor. It doesn’t have all those predators I talked about, you know, the protozoa, nematodes, and micro arthropods, and so forth. Yeah, you’re going to run into a problem. You’re going to run into where the nitrogen is being tied up by those microbes. The plants are going to suffer. But if you actually introduce those predators into the system and you’re fostering an environment where they’re going to thrive and survive, that’s when the mineralization part occurs and then we’re able to overcome that immobilization of that nitrogen in the soil. So, understanding those systems really helps us determine how and when should I use those wood chips. And that’s really what I think a lot of people are lacking is that education or knowledge about those systems to be able to effectively use wood chips.

Tom Christopher

Brian, I need to pause here for a moment to remind listeners that this radio station is WESU 88.1 FM. And this program is Growing Greener, a weekly conversation about gardening in partnership with nature. This is your host, Tom Christopher. And today I am speaking with Brian Vagg of the Compost Academy about a new perspective on gardening with wood chips.

So, Brian, what strikes me as really interesting about your perspective on wood chips is that you don’t have to go out for some sort of special inoculant to get those predators and other organisms you need to help return the nitrates taken up by the fungi and bacteria as they decompose the wood chips and re-release them back into the soil. You’re inoculating them into the soil, all of the system you need, all of the microflora you need, when you apply or when you dig in aged wood chips. Is that correct?

Brian Vagg

Yes, for sure. So, you know, the process of decomposition, especially with like a wood chip pile, if you’re going to have a wood chip pile sitting there, it’s going to come with already some amount of inoculation, right? So those wood chips, the woody material itself is going to have bacteria and fungi that were existing on the surface of the trees. And in a number of cases, there’ll be protozoa and micro arthropods and nematodes that will be mixed into there as well. Now, the initial part of the decomposition process could start off slow, especially if you’re not trying to inoculate that wood chip pile. But over time, what’s going to happen is the material is going to break down. The community of protozoa, nematodes and microarthropods are going to start to migrate into that pile. And the longer you age it, the more you’re going to find that community starting to develop.

Now, you can jumpstart it. And compost is probably the most effective way to jumpstart this process. What we tend to do is we’ll take a highly biological compost and we’ll make a compost extract. And all that really is, it’s just taking compost, washing the surfaces of that compost and the biology. It gets into the water column. So that would be the bacteria and the fungi and the protozoa and the nematodes, microarthropods and now to a liquid amendment. And then we can soak the wood chip pile to accelerate that process. But you don’t have to. The longer you let those chips age, the more the natural flora and fauna are going to migrate and then start to establish themselves in that wood chip pile.

You know, for me, when I get chips that are dropped, especially if I don’t know the source, especially with arborists, they could cut down a whole variety of trees. And I may say, you know what, for those chips, I’m going to have a minimum of six months that I want to sit in a pile and let the decomposition process start before I want to use them in any kind of soil mixes and those types of things. Right. And so just having a setup in your environment will help you get to that spot where, wow, now I have kind of a functioning ecosystem in the wood chip pile. Now is a good time for me to be able to use it in a soil blend.

So, you’re right. The natural flora and fauna will come and inoculate that pile almost always. If you have something that’s really highly contaminated, which is like you mentioned earlier, is probably very, very rare. That could cause some problems, but you’ll probably see that with your own observation. If the wood chips just aren’t breaking down, you’re not seeing the fungal hyphae growing in there, the darker colors of those humics aren’t starting to develop. Well, something’s happening there. So maybe you want to age those wood chips for two years before you start to use them. The decomposition process should be your guide. You’ll start to see that with your eyes, the decomposition process, your nose, the smells will change inside the wood chip pile. The feel, the texture of the material will change over time. Using those three observational skills can really help you make a determination of, ah, it’s now ready to use versus, I want to wait a little bit longer before I actually put them in my growing systems.

Tom Christopher

I’ve read advice on creating compost extracts by methods as simple as hanging a cloth bag or a netting bag of compost in a barrel of water for a while. Would that work or is that overly simplified?

Brian Vagg

No, not overly simplified. I might change the process a little tiny bit. In fact, making compost extracts is ridiculously simple and really cheap from a capital standpoint. One of my favorite ways of actually making extract here at my house is not to use a brewer. I have access to brewers. I have brewers, but when I’m making just an extract, I want to put it in my garden beds. All I’ll do is take a tote, like a 20-gallon tote, and I use compost tea bags. They’re basically these mesh bags that are 400 micron in size, so they’re going to filter out most of the particulate matter. All I do is I screw the bag onto two boards that will then sit across my tote. I’m basically hanging that bag now across my tote, and I’ll fill up about a third full of compost. I just take a garden hose with a spray nozzle, and I just stick that in the bag and move it around. The whole idea here is I’m just washing off the biology off the surfaces of the compost, and now it’s going to filter or strain through that bag, and it’s now in a 20-gallon tote of compost extract. You don’t even have to buy a compost tea bag. You can go get a paint strainer bag, and they’re super cheap. They may not be very durable. You might only get a few uses out of them, but a dollar or two, and then there you go. You’ve got your filtration. Just hanging the bag in the column of water, you’ll get some of that, but still, you’re not trying to force the microbes out or the biology out into the liquid, so I use some kind of spraying mechanism to kind of wash it off.

You could also use your hands. You just stick your hands in the bag and start massaging. That action of squeezing is going to then release a lot of that biology into the water column, so you can make extracts really, really easy, really, really cheap.

Tom Christopher

Do you need to wait before you apply it to the wood chips, or can you take it right after you’re finished with filling the tote and pour it in?

Brian Vagg

I use it right away. Typically, when I make extract, I’m going to use that extract within 24 hours. There is a thing. When you put microbes into the water column, there has to be enough dissolved oxygen, because those microbes are going to consume oxygen. Most of what we’re talking about is aerobes, so these are aerobic organisms that need oxygen, and if you let them sit in water too long, especially if there’s a lot of microbes that can start to deplete, now all of a sudden you’ve changed the balance from aerobic to anaerobic, and a different set of organisms will start to develop in that liquid that you have. For me, when I make extract, I’m going to plan my time and say, I’m going to make this amount of extract, and I’m usually going to apply it within a 24-hour period of time frame.

Tom Christopher

When you’re aging the wood chips, does it matter whether you leave the heap in a sunny or shady spot, or would you, for instance, wet it down, water it if there’s a drought going on? Is there any special treatment, I guess, is what I’m saying?

Brian Vagg

Moisture, moisture, moisture, moisture. We talk about this all the time. Water is essential to life, and especially the microbial communities. Soil ecosystems are essentially water ecosystems. They thrive and survive on water. For us, when we’re talking about wood chip piles, the one management aspect that I would highly recommend, if you want them to break down quicker, is to make sure that there’s moisture. It could be moisture just from rain, so you have it exposed, don’t cover it, let the water actually just infiltrate through. In fact, rain and water can do a few other things that are really beneficial to wood chips.

With wood chips, they usually come with a lot of antimicrobial compounds. This is the way that the tree protects itself from rots and diseases and so forth. And what we want to do is we want to accelerate that release of those antimicrobial compounds so that we can encourage more microbes to start to inoculate or establish in the wood chip pile. So, there will be off-gassing, the volatilization of these compounds, but then also leaching. So, when it rains, the water moving through, or when you wet it down, the water moving through will leach some of those antimicrobial compounds out of the wood chip pile. So, I don’t tend to cover my wood chips at all. I leave them out exposed. And just making sure there’s moisture in that wood chip pile is really, really important. And that will really, really move the decomposition process along. When it starts to dry out, that’s when you run into slowing down the decomposition.

Tom Christopher

I want to share an experience that I had all over the last 12 months. It doesn’t reflect particularly well on my gardening expertise, but I think it substantiates what you’ve been saying very neatly. So last fall, I was preparing a new bed for planting potatoes the following spring, this spring. And I garden in southwestern Massachusetts on a ridge of material that was deposited by a glacier during the last ice age. And you can imagine what the soil is like. It’s full of rocks. In fact, my wife and I joke that when we start a new bed, we are mining for soil. We find a vein and follow it down between the rocks. And what remains when you dig those out is sandy and very organic. So I dug in a couple of inches of wood chips, and these were well-aged wood chips. They were left by an arborist at the edge of my yard when they’d removed a couple of trees two years previously. And these were black and moist by then. But I’d done some reading online, which can be a mixed blessing. And I kept coming up on advice, oh, if you’re going to mix wood chips right into your soil, you have to really boost the nitrogen with a fertilizer. So anyway, I dug in an inch or two of wood chips, spread them out, these aged wood chips, and dug them into the soil in the bed. And I fertilized really heavily with blood meal, which is an organic nitrogen source.

Next spring, when I had the soil tested before I planted, the lab told me that the nitrate level was twice what potatoes required. And in fact, the growth of the potato plants was very fast, very leafy, and tall. And this lush growth fell prey to a fungal blight. It wasn’t healthy growth. I wish that I’d known about the difference of aged wood chips from fresh ones when I prepared that bed.

Brian Vagg

Yeah, I mean, you described very accurately the challenge you run into when you apply something like a fertilizer. In cases of a lot of plants, they have no choice but to absorb those nutrients, and those nutrients then can cause additional problems. There is a wonderful chart, I’m not sure if you’ve ever heard of it, called the Mulder chart, where they talk about the interaction between different minerals or nutrients as far as plants are concerned. And there are many cases where if a plant takes in too much of one mineral or nutrient, it will block the absorption of other minerals and nutrients and cause other stressors in the plants.

And once the plant starts getting under stress, then the disease and pests are able to readily attack those plants. You know, sometimes I see corn growing and it’s just this really dark bluish green. I’m like, ooh, that’s a recipe for disaster. There’s too much nitrogen in those plants. They’re going to attract a lot of pests. So in that case, what’s a farmer going to do? All right, well, I’m going to apply a pesticide. Well, it’s that cycle of always applying these things that then degrades the system even farther, right? And so just backing off away from those things and then just allowing the microbial community to thrive and to flourish, that’s where we really start getting highly vigorous plants that have really tuned immune systems that really help us prevent against pests and disease problems. So probably if you just use those wood chips, they’re probably inoculated really, really well. Those really aged wood chips, you probably wouldn’t run into the problem of having what you saw with that super green leafy growth. But then, yeah, the plant still ran into problems.

Tom Christopher

I guess in closing, I’d like to ask you if listeners want to learn more about your work and more about Compost Academy, how would you suggest they do that?

Brian Vagg

First, I would say go to our website. We have just compost.academy. There are free sources. We actually have a free course. It just touches on the surface a lot of things we talked about here today, but they’re free. So, you can go out there and take those free courses. And then if you decide that you want to know more, you can definitely sign up with one of our courses. We also have a YouTube channel where we have a lot of content around success stories or stories about the work that we’ve done professionally.

The other part of my job is I am an educator through Compost Academy, but I’m also a soil health consultant. I have clients that exist in both the regenerative space and agricultural space. And we’ve taken a number of those stories and the work that we’ve done in that space, and we have them on our YouTube channel. And I know that it helps because a lot of times people look at these regenerative systems. It’s like, well, how does this work or does it work? I mean, I’ve heard things, but then to go see some proof positive stories really does help solidify, okay, these things are possible. We have an Instagram handle as well. So, we post a lot of content there. So, there are a lot of ways that you can actually find us. And I definitely welcome you to join one of our webinars. We do some free webinars about once every three or four months. So, come check those out too.

Tom Christopher

Okay, this all sounds great. Thank you very much. Before we close, I want to share a tip about locating a source of wood chips in your area. By calling local arborists, gardeners can often find tree companies who are looking for sites to dispose of truckloads of wood chips. However, in some areas, securing delivery wood chips can be competitive. And in that case, you may want to use the online service ChipDrop. You’ll find its homepage at chipdrop.com. ChipDrop may not provide a service to gardeners in lightly populated areas. But in most communities throughout the United States and Canada, when you have established an account with ChipDrop, you may submit a request for wood chips, and ChipDrop will forward your request to local arborists in its network. When one of the member arborists needs to empty its truck, it may select your address as a dump site. You may receive as little as four cubic yards of wood chips or as much as 20 cubic yards.

Tom Christopher

That brings us to the end of this week’s Growing Greener. Please join us again at the same time next week on this radio station, WESU 88.1 FM for another episode, or listen to Growing Greener as a podcast at www.thomaschristophergardens.com. If you have comments or suggestions, please share them with me, Tom Christopher, via the same website, www.thomaschristophergardens.com. Growing Greener is produced as a community service in partnership with the Perfect Earth Project, a nonprofit dedicated to educating, engaging, and inspiring individuals, land care professionals and decision makers to adopt toxic-free, nature-based, and climate-responsible landscaping practices.

 Transcribed by TurboScribe.

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