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Soil is the Solution: Why Healthy Soil Matters for Trees · Talking Trees with Davey Tree

• 0:00
  Speaker: Welcome to the Davey Tree Expert Company's podcast, Talking Trees.
• 0:04
  Speaker: I'm your host, Doug Oster.
• 0:06
  Speaker: Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much, much more.
• 0:15
  Speaker: Tune in every Thursday to learn more because here at the Talking Trees Podcast, we know trees are the answer.
• 0:23
  Speaker: I'm joined this week by Grant Thompson.
• 0:25
  Speaker: He's a specialist in arboriculture and plant sciences at the Davey Institute.
• 0:30
  Speaker: Welcome to the show, Grant.
• 0:32
  Speaker: We talked a little bit before we came on here, and you've actually listened to the podcast, huh?
• 0:37
  Speaker 1: I have.
• 0:38
  Speaker 1: Nice to be on here.
• 0:40
  Speaker: Oh, having me.
• 0:41
  Speaker: Nice to have you.
• 0:42
  Speaker: And I can see we we have video, you guys can't see it, but you're at the seed campus, right, in Kent, Ohio.
• 0:48
  Speaker 1: That's right, I am.
• 0:49
  Speaker 1: I'm a research soil scientist here at the Institute.
• 0:52
  Speaker: Tell me a little bit about the Davey Institute and what that is.
• 0:56
  Speaker 1: Sure, the Davey Institute is a research and development arm of Davey.
• 1:01
  Speaker 1: We help all the service lines do what they do with inside uh information and science-backed work.
• 1:08
  Speaker: And so you have been studying urban soil and soil compaction, right?
• 1:15
  Speaker 1: That's right.
• 1:16
  Speaker 1: Uh, I've spent my career between landscape architecture, horticulture, and soil science.
• 1:22
  Speaker 1: We know that if roots have trouble growing in soil, the plants are gonna have trouble too.
• 1:28
  Speaker: That makes good sense because as somebody who talks about trees and also about uh gardening, we always say soil is everything.
• 1:37
  Speaker: What is your tagline, though?
• 1:38
  Speaker: I know you've got a special one.
• 1:40
  Speaker 1: Well, uh, here at Davey, we like to say that trees are the answer.
• 1:44
  Speaker 1: I'd like to add that soil is the solution.
• 1:47
  Speaker: I love that.
• 1:48
  Speaker: That is so awesome.
• 1:50
  Speaker 1: I'm waiting for stickers to get made.
• 1:52
  Speaker: All right.
• 1:53
  Speaker: Well, we're gonna we're gonna start a a campaign right now.
• 1:57
  Speaker: Soil is the solution.
• 1:58
  Speaker: I love that.
• 1:59
  Speaker: Um, so tell me a little bit about your research.
• 2:02
  Speaker: What does that entail when when you're looking at soil compaction and what that means for for trees and for our landscapes?
• 2:10
  Speaker 1: Absolutely.
• 2:11
  Speaker 1: Well, here at the seed campus, we have what I think is one of the largest compaction studies that I'm aware of.
• 2:17
  Speaker 1: We have two acres of space dedicated where we have our native soil here.
• 2:22
  Speaker 1: Uh, our campus was prior a golf course, so it's pretty good alluvial stuff, uh, good for growing grass and trees.
• 2:29
  Speaker 1: And the other part of the research plots, we've scooped out 16 to 18 inches of the native soil.
• 2:35
  Speaker 1: We've replaced it with subsoil from the building here as it was being built when they were excavating the basement.
• 2:43
  Speaker 1: And that subsoil has been placed in those plots and then compacted to the level that you would see on a lot of uh typical construction sites.
• 2:52
  Speaker 1: So it's low organic matter, low nutrient, uh pretty stony and uh pretty pretty hard.
• 2:59
  Speaker 1: Uh to those plots, we've added different soil amendments uh so we can see some of the practices that we advocate here for at Davey.
• 3:08
  Speaker 1: And this spring we planted 1,600 bare root trees of five different species into those, and we'll be looking uh at how those trees grow and the soil changes over the next uh many years, hopefully.
• 3:21
  Speaker: What's an example of how you would change some of the soil?
• 3:24
  Speaker 1: Sure, we've done some different amendments where what we would call soil renovation, where we've added compost and biochar and done some decompacting to uh fluff up the soil and get some more pore space in there.
• 3:37
  Speaker 1: We've done things like vertical mulching, that is where we in targeted areas go down uh up to three feet and backfill with biochar, but that's just kind of punching holes through the hard spots of the soil.
• 3:51
  Speaker 1: We've done uh applications of just compost or biochar mulch on the surface, some kind of typical fertilization, and we also have uh unamended controls so we can see if we did the do-nothing approach, what that looks like for those different uh the compacted and the uncompacted soils.
• 4:11
  Speaker: How long has this research been going on at Seed Campus?
• 4:15
  Speaker 1: Well, the initial plots were developed uh a couple of years back uh working with Dr.
• 4:21
  Speaker 1: Chris Fields Johnson on that.
• 4:23
  Speaker 1: The trees went in in the spring of 2026.
• 4:26
  Speaker 1: So this is really part of our establishment phase.
• 4:29
  Speaker 1: We need to get those trees growing to be able to use them as reporters for how the soil conditions are and what are different uh amendment or remediation practices, uh, how they're doing.
• 4:42
  Speaker: How long do you think it will take until you know or or can you tell something already?
• 4:47
  Speaker: Or I guess that's that's the question, huh?
• 4:51
  Speaker 1: Yeah, it's pretty obvious.
• 4:52
  Speaker 1: If anyone's uh been around a recent home development or a construction project, those trees and the compacted soils are struggling.
• 5:02
  Speaker 1: They are small, they don't have a lot of leaves, pretty sickly looking.
• 5:07
  Speaker 1: Uh so right now we really are seeing the major effects of the uncompacted and the compacted soils.
• 5:13
  Speaker 1: The different remediation practices that we've tried, uh amendment practices.
• 5:18
  Speaker 1: We're starting to see some differences there, but I think it'll take a couple of more years to to get over just seeing the major effects of compacted soil.
• 5:27
  Speaker: Well, this is great research because uh there's so many places that we have to plant in these areas, and I think it still is not uh mystery is the wrong word, but I think it's there's a lot of different ways that people deal with that type of compaction, and when it comes to planting, and in my mind, I think almost every arborist does it a little bit different.
• 5:53
  Speaker 1: Yeah, it's uh something that I experienced in my career as a landscape architect.
• 5:58
  Speaker 1: You know, anytime we develop a site, we're driving equipment across it, we might be removing topsoil or organic matter because we don't want uh settlement in our structures or foundations or roads, utilities.
• 6:13
  Speaker 1: And eventually the contractor is maybe putting back good soil and we're planting into it.
• 6:20
  Speaker 1: Um, and arborists and other folks, homeowners, are going to be caring for those sites for years to come.
• 6:27
  Speaker 1: It takes a lot of work to undo some of the things that we do to soil.
• 6:32
  Speaker: Yeah.
• 6:32
  Speaker: When does a contractor put good soil back on?
• 6:36
  Speaker 1: That's a good question.
• 6:37
  Speaker 1: I don't think I see it too often.
• 6:39
  Speaker: No, you see it so often, uh in like just even in home construction where a farm field is stripped, uh, they bring in, you know, uh house after house after house and throw grass seed down, throw a couple trees in, and say good luck.
• 6:57
  Speaker 1: Yep, exactly.
• 6:58
  Speaker 1: As I say, that's the uh sod on clay mentality.
• 7:01
  Speaker 1: It uh doesn't work so well.
• 7:02
  Speaker 1: But yeah, I think there's a lot that can be gained from good soil care.
• 7:07
  Speaker 1: I try to remind folks here that uh soil care is a form of plant health care.
• 7:12
  Speaker 1: Nine times out of ten, I'd rather pay for good soil work and then plant smaller plants uh and give them a real chance at success.
• 7:22
  Speaker: That's such great advice, and that advice has been repeated over and over again.
• 7:27
  Speaker: You know, spend twenty dollars for your planting hole for a five-dollar tree.
• 7:32
  Speaker: That you know, that's a that's an old saying.
• 7:34
  Speaker: And knowing though, exactly what should be put in that soil to me is is incredibly valuable.
• 7:44
  Speaker 1: Right.
• 7:44
  Speaker 1: Well, good organic matter, whether that's fresh compost, compost derived from leaves or um food waste, is a good start, manure products.
• 7:56
  Speaker 1: Uh biochar certainly is another part of that.
• 7:58
  Speaker 1: That gives us long-term soil drainage, long-term soil structure.
• 8:04
  Speaker 1: Uh, that biochar is not degraded by microbes the way that compost is, so they're really serving different purposes in the soil.
• 8:12
  Speaker 1: So it's a both and, not an either-or.
• 8:14
  Speaker 1: And first and foremost, we got to decompact because it doesn't really matter what our soil amendments are.
• 8:21
  Speaker 1: If the roots don't have pore space to grow through, they're not going to get to whatever we just added.
• 8:27
  Speaker: Are there other types of compaction besides like big machinery coming through, or that's the main thing we're looking at?
• 8:35
  Speaker: Because that's that's incredible compaction.
• 8:38
  Speaker 1: Well, certainly any major equipment will do it.
• 8:41
  Speaker 1: Uh, if you're parking cars on your lawn periodically, that can do it.
• 8:46
  Speaker 1: If you're doing regular turf management, particularly if it's been wet, you have a greater chance of compacting soil.
• 8:54
  Speaker 1: And I know I've got a spot in my yard where I walk around my garage that's probably compacted just from too much foot traffic.
• 9:01
  Speaker 1: So it can really happen for a lot of reasons.
• 9:04
  Speaker 1: Um just regular management.
• 9:07
  Speaker: Is there something a homeowner can do if they have compact if they know they have compacted soil?
• 9:13
  Speaker 1: Absolutely.
• 9:14
  Speaker 1: Well, you know, certainly that's something an arborist uh like some of our Davey folks could help you with.
• 9:19
  Speaker 1: You can do uh core arification.
• 9:22
  Speaker 1: You've seen that probably where the um they pull small soil plugs out of the lawn and leave it there, uh kind of look like dog droppings sometimes.
• 9:31
  Speaker 1: Those can get works back into the soil, that's good.
• 9:34
  Speaker 1: If you can't actually get into the soil, even top dressing with uh compost and biochar is another way to eventually improve the soil.
• 9:44
  Speaker 1: Uh doing it just on the surface is kind of what nature does when we return litter or leaves at the end of a season, but getting it into the soil is really the best way.
• 9:53
  Speaker 1: Now, if you got big trees and tree roots, uh things you want to be a little more careful about, that's really something you want to call a specialist for and get us in there.
• 10:02
  Speaker 1: We have certain tools that we can do that uh without harming the tree or tree roots.
• 10:08
  Speaker: Is biochar something you would consider that is new in the industry, or is it something you've dealt with for a long, long time?
• 10:18
  Speaker 1: Yeah, it's something that I've been around for a long time.
• 10:20
  Speaker 1: Uh in my graduate career, one of the international leading researchers of biochar was doing some of the work at the university I studied at.
• 10:29
  Speaker 1: Uh, so I've been around biochar long before Davey.
• 10:32
  Speaker 1: Biochar has a longer uh track record in the agriculture space, you know, where you're looking at crop yields and have some pretty definitive ways to look at that.
• 10:42
  Speaker 1: Uh biochar in the I'll say green or landscape industry, that's newer.
• 10:48
  Speaker 1: I think there's a lot of interest.
• 10:49
  Speaker 1: There's also a lot of questions about what it is, what it isn't, what it can be, what it's not, what it does.
• 10:55
  Speaker 1: Uh, and that's all some things we are uh working on and incorporating in our work here at Davey.
• 11:02
  Speaker: When you look at those research plots, could do you have a guess ahead of time, or do you have to to just look at the data?
• 11:10
  Speaker: Like when you set up the plots and you're like, you know, I got a feeling that when I put compost and biochar in there, those trees are gonna go nuts, or do you have to just look at it from a science point, like I have to look at the data, I I can't do that.
• 11:25
  Speaker 1: I try to do both.
• 11:26
  Speaker 1: I mean, obviously, when we set it up, we pick some treatments that we know are gonna do poorly, or our typical practice because we need to have those to compare against.
• 11:37
  Speaker 1: But we know that when we do decompaction and we add good organic matter, compost, and biochar, we're pretty sure we're gonna see good outcomes.
• 11:45
  Speaker 1: Now, it's really nice when the data show that as well.
• 11:49
  Speaker 1: That's what we'd like to lean into to make science-informed decisions.
• 11:54
  Speaker: But I I mean, because you're using science, it could be where you look at one of those plots and say, Well, you don't need quite that much compost to biochar.
• 12:03
  Speaker: Look at how this tree's doing.
• 12:04
  Speaker: I mean, I that's a surprise.
• 12:05
  Speaker: Exactly.
• 12:06
  Speaker: That's a surprise.
• 12:08
  Speaker 1: It is, and science will surprise you all the time.
• 12:11
  Speaker 1: Biology doesn't always behave the way that we think it should.
• 12:14
  Speaker 1: But you know, having the data to do it uh helps us inform our clients and helps our clients make good decisions, which is why we do it.
• 12:23
  Speaker: Well, by what you were saying, you've had an interesting journey to what you're doing now.
• 12:28
  Speaker: Tell me a little bit about it, how you ended up, where you ended up.
• 12:32
  Speaker 1: Yeah, I have.
• 12:33
  Speaker 1: Um, I started my career in central Iowa uh as a uh an associate landscape architect.
• 12:41
  Speaker 1: Got really interested in why the planting designs uh we came up with didn't always work the way we thought they would.
• 12:48
  Speaker 1: Turns out soil and soil compaction is a big part of that.
• 12:52
  Speaker 1: Went through uh to a master's and a PhD in soil ecology, looking at how land use changed in Baltimore County, Maryland.
• 13:01
  Speaker 1: When you take forests and farms and make those into residential spaces, how does the soil change?
• 13:07
  Speaker 1: Ended up back in Iowa, uh in the Department of Horticulture at Iowa State University, teaching plant materials, uh install management, a lot of the kinds of things uh that I would do in in horticulture or as a landscape architect.
• 13:24
  Speaker 1: Ended up back in practice and finally here at Davey.
• 13:28
  Speaker 1: So it's uh been through through practice and through research.
• 13:32
  Speaker 1: So I've got skills on both sides.
• 13:34
  Speaker: Oh, that's awesome.
• 13:36
  Speaker: How how many different areas are there where the research is happening that you set up like specific types of soil?
• 13:46
  Speaker 1: Yeah, so uh we have one large uh two-acre research plot here where we're doing the study that I described, but we do uh work on soils all over um and are trying to figure out ways that we can embed research into like some of our Davey resource group projects or other um other right projects we do for our clients.
• 14:11
  Speaker: When we're talking about soil compaction, what should we be looking for on our landscapes?
• 14:16
  Speaker: Now, in my case, I have an arborist from Davey comes every six months.
• 14:21
  Speaker: He's looking for that sort of thing.
• 14:23
  Speaker: And you should have somebody come at least once a year out there.
• 14:27
  Speaker: But we know everybody doesn't do that.
• 14:30
  Speaker: What are some signs that the soil is compacted?
• 14:34
  Speaker 1: Yeah, that's a great question.
• 14:36
  Speaker 1: Uh, I think one of the easiest things we can do is notice how water moves.
• 14:41
  Speaker 1: If it is standing or pooling on the surface of your soil, uh, you may have some compaction because the water can't infiltrate or move down into the soil.
• 14:51
  Speaker 1: You might also notice some patches of pretty bare turf, thin turf.
• 14:56
  Speaker 1: And sometimes even some weeds, like broadleaf plantain, is another indicator of soil compaction.
• 15:03
  Speaker 1: It does well and is more competitive with turf when you have soil compaction.
• 15:09
  Speaker: What do you hope for your research?
• 15:12
  Speaker 1: Well, I hope to be able to give our clients more evidence and reassurance that you know spending more on their soil is really good for their plants.
• 15:20
  Speaker 1: You know, a lot of times we get called there because the plant isn't doing well, and that may come right back to the soil.
• 15:27
  Speaker 1: But sometimes that's a hard decision to make for our clients, and I hope this data will help them make those decisions with greater confidence.
• 15:35
  Speaker: Well, Grant, as we always say in the Talking Trees podcast, soil is the solution, right?
• 15:40
  Speaker 1: That's right.
• 15:41
  Speaker 1: Trees are the answer, and soil is the solution.
• 15:44
  Speaker: When you get those stickers, when they finally print those, I need some of those.
• 15:48
  Speaker 1: I do too.
• 15:49
  Speaker 1: I'm looking forward to it.
• 15:50
  Speaker: All right, Grant, thanks so much for the information.
• 15:53
  Speaker: Good stuff, and keep up the good work.
• 15:55
  Speaker: Uh, I can't wait to hear about the results.
• 15:57
  Speaker: We'll we'll talk again.
• 15:59
  Speaker: Uh when?
• 16:00
  Speaker: When when should we talk again about these results?
• 16:03
  Speaker 1: Well, I expect to be able to say something a little different every year, but I'm looking forward to good stuff.
• 16:09
  Speaker 1: Thanks.
• 16:10
  Speaker: All right.
• 16:10
  Speaker: Great to talk to you.
• 16:11
  Speaker: Thank you.
• 16:12
  Speaker: Well, Grant's work is truly groundbreaking.
• 16:15
  Speaker: Get it?
• 16:16
  Speaker: Now, tune in every Thursday to the Talking Trees Podcast from the Davey Tree Expert Company.
• 16:21
  Speaker: I'm your host, Doug Oster.
• 16:23
  Speaker: As always, I would love for you to subscribe to the podcast so you won't miss a show.
• 16:27
  Speaker: And we'd love to hear from you.
• 16:29
  Speaker: You can send us an email to podcasts at Davey.com.
• 16:33
  Speaker: That's P-O-D-C-A-S-T-S at d-a-v-e-y.com.
• 16:38
  Speaker: You can also click the link at the end of our show notes to text us a fan mail message.
• 16:43
  Speaker: Your ideas could be on an upcoming show.
• 16:46
  Speaker: And as always, we'd like to remind you on the Talking Trees podcast.
• 16:50
  Speaker: Trees are the answer.
• 16:52
  Speaker: And for this podcast, soil is the solution.