All Things Soil: Types, Testing and Why it Matters

Jason Parker, district manager of Davey's Warminster office, talks about why soil is so vital for a healthy landscape, as well as which plants are best for certain types of soil and how to keep soil healthy. 

In this episode we cover: 

• Most common types of soil in Philadelphia (1:27)
• Topsoil from new developments (1:58)
• Soil testing (3:14)
• How to properly plant trees in soil (5:20)
• Older neighborhoods usually have better soil (7:07)
• Should you do a soil test in a wooded area? (8:02)
• Different trees need different soil pH levels to grow (9:42)
• Based on your soil, choose your trees and plants wisely (11:04)
• Best species for low quality soil (13:16)
• Swamp white oak vs white oak (16:44)
• Leaving fallen leaves on the ground is great for soil (18:24)
• Best soil care processes (19:40)

To find your local Davey office, check out our find a local office page to search by zip code.

To read our soil blogs to ensure your soil is happy and healthy, visit Blog.Davey.com by clicking here - Tree Care Tips, News & Checklists

Connect with Davey Tree on social media:
Twitter: @DaveyTree
Facebook: @DaveyTree
Instagram: @daveytree
YouTube: The Davey Tree Expert Company
LinkedIn: The Davey Tree Expert Company 

Connect with Doug Oster at www.dougoster.com. 

Have topics you'd like us to cover on the podcast? Email us at podcasts@davey.com. We want to hear from you!

Transcript

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Doug Oster: Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oster. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much, much more. Tune in every Thursday to learn more because here at the Talking Trees podcast, we know trees are the answer. Before we get started today, we are looking for your tree questions. We would love to do a whole episode where arborists are answering your questions. That might mean just sending a question in via email, or maybe I could record you asking a question.

Reach out to us via email at podcasts@davey.com. That's P-O-D-C-A-S-T-S @ D-A-V-E-Y.com, or you can click the link at the end of the show notes to text us a fan mail message. Again, your ideas could be on a future show. This is going to be fun. Okay, onto the show. I'm joined again this week by Jason Parker. He's a district manager of the North Philadelphia office of the Davey Tree Expert Company. Today, we're talking about different types of soil, how and why to test your soil. Jason, welcome back. How are you?

Jason Parker: Hey, Doug. I'm doing good. Thank you very much.

Doug: Anybody that's planting anything knows that soil is everything. Let's talk about the different types. What do you deal with there in the Philadelphia area?

Jason: We have a lot of newer developments that typically have had topsoil stripped off, so we're left with a bunch of junk, to put it plainly. Have some older developments that are maybe in a little bit better shape but most of them need help is what we've found. We've done tons of soil tests all across Bucks and Montgomery counties, and they all tell us the same thing, that they all need help. We do our best to provide that.

Doug: Let's start off with that new construction. What are they doing? They're just stripping everything off the top. Then, was it a farm field or whatever it might have been? It's just all gone. What's left that's called junk? What is it that's left?

Jason: Absolutely. It's very interesting. They take everything off. They push it all into a big pile. As these developments are being built, you see those big piles. Everybody thinks it's going to get spread back around once the construction's done. That generally is not the case. Most of it goes away and is sold off and just a little bit is left. We do a lot of work, especially around new plantings and new developments like that, because the plants are struggling so much. We come in, we provide some soil care services, air tool work, things like that. What we have found is somewhere between maybe two, and if you're lucky, four inches maximum of something that resembles actual topsoil. Most of the rest, at least in our area, is very heavy clay.

Doug: That's what we have out here on the other side of the state, clay or shale. Let's talk a little bit about a soil test, the importance of it, how you do it, and why it's so important.

Jason: Soil tests can tell you a lot about what you're working with, which is certainly a good starting point. We talk about right tree, right place. If you don't know what the soils are like, then you may not be able to pick the right tree. Being that we've done so many soil tests in my area, it makes it fairly easy to make an educated guess without even doing a soil test. There's a lot of places you can get them done for free. I think Penn State does a lot of free soil testing. They'll give you the basics. You really don't need more than the basics most of the time, unless you have a very odd situation.

Mostly you want to know what soil type you have and roughly what the pH is. That'll give you an idea of what is survivable there. Do you start to get into the minute details, like the micronutrients and things like that that show up on a more serious soil test? Those might actually end up causing you more problems in the future if you're trying to manipulate those micronutrients. There's very little reason to actually get involved at that level.

Doug: What's interesting to me there is that I was thinking soil test, then try and change what's there. The other way to look at it is soil test to see what could grow there. That I didn't think about.

Jason: Yes. You can certainly do both. The thing to understand about soils is changing them. Even changing pH in soil. We do a lot of turf work in my area. Changing the soil pH takes a lot of work over multiple years. That's fine if you're committed to that. There may be a better solution than just finding something that'll grow in what you have.

Doug: That makes good sense. Now, I've been taught that when I'm planting anything except a tree, that we add compost to the planting hole. With a tree, what do you do? I know that some people say, well, that just makes a big container and the roots won't spread out. Other people are saying maybe you can incorporate some organic matter in there. I guess it depends on what you find in your soil test.

Jason: Yes, definitely. I think most people are going to find that the organic content of their soil, unless they are on an undisturbed farm, is probably fairly low. You think about it, even our leaves, we rake them up, we take them off of the property most of the time. You're not getting that recycling effect from the tree leaves. It is a good idea. You got to be a little bit careful with too much organic content. You can create that bowl, especially here where we have a lot of clay soils. You put something in that might percolate water very easily but then it's in a clay container and it's acting like a pot.

Most trees, a few exceptions, are not going to tolerate what we call wet feet. You don't really want that. The other thing is just from a practical standpoint, you're trying to get the tree to stand up. A lot of the compost materials are very light and airy and they don't provide the same level of support like a topsoil would. You may end up with a tree that starts leaning or something like that. That's easy to correct when the tree is young but if you let it go too long without correcting it, you're going to have problems in the future.

Doug: Another interesting thing I thought you said was when you go to an older, more established neighborhood, it sounds like you're stumbling onto, in general, better soil. [chuckles]

Jason: In general, they've had, most of the time, years to recover from that initial construction. When we're getting into the newer developments, I'm talking 10, 15 years, the construction impacts are still very obvious, biggest thing being soil compaction from all that heavy construction equipment. An older neighborhood may have gotten through some of that a little bit. Trees are a little bit bigger, a little more established. You're getting less compaction. It's working itself out to a degree but definitely tend to be better soils.

Doug: You'd love to plant where I'm at because I don't rake the leaves and I'm living in a forest and the leaves just do their thing. When I lose a big tree, I just stick in some other native and it seems to do well without a soil test. Should I be doing a soil test, though, in those areas? What I'm thinking is, okay, I say it all the time, declining oak forest. That's where I live. Just had a huge storm come through. I lost two giant oaks again. I want diversity in my forest. I'm putting other natives in, other trees that I might love. Should I be doing a soil test?

Jason: You can for your own purposes but in terms of really having an impact on what you're going to do-- You're doing the right stuff already, Doug. Looking at natives and things like that, they're always going to do the best. We know that because they're native to the area. That's exactly what they are. You probably don't need it. It's an interesting thing. I know you and I we get very into the tree thing. For us, that's interesting. For other people, maybe not so much. If that becomes a burden, I don't think they really need to go through all those steps. Again, you get a good arborist out to your property, they're going to direct you in the right path anyway. They may choose to do a soil test and there's nothing wrong with that. I just don't think it's critical every time.

Doug: Yes, I guess it just depends on what part of the property you'd be looking at and what you might be putting in. Let's say in the case you do do a soil test and let's first talk about pH. As you've said and as I've learned, pH is very difficult to change and it takes years. What does that mean as far as what kind of tree that you can put there? Are you looking for a certain tree for a certain pH or are you just looking for a tree we know this tree is really tough, it can grow in a lot of different pHs?

Jason: Hopefully, we're looking for the really tough trees that we know are going to do really well. Some people have some very specific trees that they're looking for. Of course, with the internet, everybody can go on and pick out the exact variety of the crab apple that they want, and it might not even be something you can find locally. That's where you lean on your arborist and have them give you some thoughts as to what does well in the area.

Having done hundreds if not thousands of tests across the Philadelphia market, we have a good feel for what the soil is like and what will do well here. We can make pretty good recommendations for you. I would say to the homeowner, don't get your heart set on something so specific because it might not be the right tree for the right place, and then you're going to regret it down the road.

Doug: Well, it's so interesting that you bring that point up because so often, in my world doing the garden stuff, I get the same thing where I get people that have read about it in a magazine. It might not even be released yet. The other thing is, who knows how it will really do? Yes, when every new tree or new plant is introduced, it's the greatest thing since whatever. Until it proves itself after a few years, maybe a few decades, we don't know if it's really going to be all that.

That's the other thing about dealing with an arborist, working with an arborist. They know what's available, as you said. They also know what's tried and true. You don't want to take wild chances when you're putting a tree in. This is a long-term proposition, right?

Jason: Right, and it's a significant investment most of the time. Why would you not want to give it the best chance that it possibly could? Things like ash trees are a great example. They were planted as street trees. They looked really nice. Everybody thought they were a great deal. Then we had an insect come through and wipe a great portion of them out. That has happened, unfortunately, over and over and over again. I don't think it's going to stop. Being smart about it certainly makes a lot of sense.

You're right too, the plants that have just come out, nurseries are constantly making new varieties in the hopes that they're going to be better, showier, more fruit, whatever, than the past. That doesn't always pan out. Giving them a little bit of time to establish themselves as a good plant. You'll often see that something comes in for two or three seasons and next thing you know, your nursery's not carrying it anymore. There's a reason for that.

Doug: Sometimes they're as great as they say, and sometimes they aren't. Sometimes when you're breeding something like a different type of flower into a tree, you're losing something else. You're losing that amazing hardiness that the straight species might have had. Let's discuss some of the tough trees that you can put in these situations. As you said, and as we always say, right tree, right place. When you go into a new development or you see an area where the soil isn't that great but they need shade or they need beauty, whatever they want that tree for, let's talk about some species that you like to use when you find the right spot for them.

Jason: Yes, got you. There's a bunch that I like. Shade trees are the ones that require the most thought. Most ornamentals, you're going to put in a bed around the house. They're going to be smaller. You still want to pick the right ones but they tend to be a little bit easier, maybe a little bit more variety available. One of the great ones, I think, is the London plane or the sycamore. There are things that you have to be aware of. That does produce a fair amount of pollen. It produces a fruit, so you probably don't want it over the back patio. If you've got a spot, it's a great quick-growing shade tree.

It's got the interesting camouflage-looking bark, which is interesting even in the winter months when it doesn't have leaves. I really like that one. I don't find a lot of great places to plant it because we're typically on smaller properties that it just isn't practical for. A little more practical trees. I love most maples, red maples, sugar maples. They're pretty quick growing. They're not a super expensive tree. They've got great fall color. Other than girdling roots being the one thing you really got to watch out for on them, they tend to be pretty hardy, pretty insect and disease-free.

Doug: You arborists and your sugar maples. You all love sugar maples. That's a good thing to know. I usually expect a lot of times when I interview arborists some weird plant I've never heard of before. Boy, that sugar maple comes up a lot because of the fall color, ease of growth, plenty of shade. People always ask me, and I say this all the time, what to grow under that maple? I said a bench. Grow a bench.

Jason: Yes, exactly. I think one of the other ones that I go to a lot is either a pin oak or-- I generally don't do straight white oaks but I'll do a swamp white oak in a lot of scenarios. Not as quick growing, so you got to take that into consideration. You do have potential for acorns. You want to make sure that you're taking all of the facets of the tree into consideration when you're making those decisions. They tend to do pretty well here.

We don't have a problem in my area of gypsy moth anywhere near as bad as we do in some areas in Pennsylvania where maybe the white oak wouldn't be a good tree for you. The pin oaks, they can get a disease called bacterial leaf scorch but they tend to be a little bit more resistant to it than the straight red oak species. Those are a couple that I go to on a pretty regular basis.

Doug: Tell me about the swamp white oak and why you prefer it over a straight white oak, because I don't know the difference between the two. School me on that if you could.

Jason: Sure. Honestly, most people wouldn't. Even most arborists couldn't show you the difference between two that were planted side by side. To me, structurally, the straight white oak is a little bit more-- I don't know what the best way to put it is. It has a little bit more even shape to the canopy, whereas the swamp white oak is a little bit more natural. In an urban setting, the straight white oak, I think, looks a little bit more typical, whereas the swamp white looks a little bit more native. That's my take on how I tell them apart. The biggest thing quite honestly though, is straight white oaks are very expensive and typically fairly hard to get. The swamp white is what most people carry. That's just a practical standpoint.

Doug: When I hear the word swamp, though, in the name, I'm thinking it needs wet feet. No, not in this case?

Jason: No. It'll tolerate slightly wetter conditions. Again, when we're talking soils, drainage is a really important part. That's something that you definitely want to consider. If you have the wet soils, then there are other species that we should be going to. Swamp white would be okay but it wouldn't be something that I would specifically plant in a wet spot. I'd go with a river birch or a weeping willow, something like that, in those really wet spots.

Doug: Since we're discussing soil, let's talk about leaving those leaves, if you can. We all know that in the forest, the leaves fall year after year. They decompose. They feed the tree. Everyone's happy. That's not so much in the urban landscape.

Jason: Right. Obviously, that's best-case scenario. If you create a large enough mulching around the tree and maybe rake everything into that mulching, maybe you'll be okay with it. Township ordinances and things like that, though, get in the way sometimes of some of that stuff so you end up being limited. We can recreate that forest situation for your soil through soil care processes that aren't going to maybe get you in trouble with the township or the wife or whoever it might be and keep your property looking nice at the same time without leaves blowing all over. There are ways around that. Obviously, if you could, it would be great. It's obviously less work for you too, not having to haul them off. There are ways around it that we'll get the soil where we want it to be for sure.

Doug: Let's talk about them. Although, I do like the less work part. That's my goal in my yard, less work.

Jason: Yes. Honestly, that goes into the planning stage of things. Nobody has a ton of time. People enjoy spending time in their gardens but your time is always limited regardless. If you can make it manageable by picking the right tree and putting it in the right place, then that'll go a long way. In terms of things that you can do to the soil, we do a lot of air tool work out here, which helps do a couple of things. It really helps break up compaction. It'll also expose things like girdling roots that we can then deal with.

Doug: In that, you're blowing the soil away. Do I have that right?

Jason: Yes, that's correct. There's a lot of different processes that use an air tool. One is simply a root collar excavation, which is looking for that girdling root. You're just going right around the trunk of the tree because that's where a root is strangling potentially the stem. Then there's radial trenching, vertical mulching. Those are more related to the soil care side of things that we're discussing. You're going to then backfill with some sort of amendment. As the tree gets bigger, maybe when you planted it, you put some organic content around the tree but now the tree's gotten bigger, the root zone has gotten bigger.

You've just had construction, and now you've got compacted soils. All those kinds of things can be handled with that. Then there's a ton of different amendment options. Biochar is becoming a big thing for sure, not just in our industry but in agriculture and other fields, actually being used a lot in construction as well, from what I understand. Does a lot to really help make a better soil profile. Better soil profile.

Going back to that soil testing, if you did a real detailed test, you'd find that most of our soils aren't missing those micronutrients that I was talking about. They're there. When you have things like carbon that are part of the soil, they can help break down some of those bonds that lock up those micronutrients and make them not available to the plant. I know I'm getting nerdy and sciencey there but there's a lot that can be done to really help improve our soils with the air tool use for sure.

Doug: All right, Jason, good stuff. As always, appreciate your time. It was great to talk to you again.

Jason: Yes, very good. Thank you. I appreciate it, Doug.

Doug: Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host, Doug Oster. Do me a big favor, subscribe to the podcast so you'll never miss a show. We would love to do an episode with your questions on it. Got a question for an arborist, there's a couple different ways to reach us. Send us an email to podcasts@davey.com. That's P-O-D-C-A-S-T-S @ D-A-V-E-Y.com. You can also click the link at the end of our show notes to text us a fan mail message. Your questions could be on a future podcast. We'd love to hear from you. As always, we like to remind you on the Talking Trees podcast, trees are the answer.

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