Why Trees Fail - Environmental Factors & Things We Do

Rob Dallmann from Davey's Annapolis office talks about the reasons why a tree could fall and how arborists have to be "history detectives."

In this episode we cover:  

• A fallen tree in Rob's neighborhood (0:44)
• Looking at the history of the scenery (1:11)
• Events that can contribute to a tree falling (4:33)
• The importance of an arborist looking at your trees for expert opinions (7:43)
• How homeowners contribute to a tree falling (11:42)
• Treating your trees like your pets (14:15)
• How environmental factors play a role (14:56)
• Oak decline (16:26)
• The importance of tree diversity (19:55)

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Connect with Doug Oster at www.dougoster.com. 

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Transcript

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. I'm joined this week by Rob Dallmann. He is a district manager at the Annapolis, Maryland office of the Davey Tree Expert Company, and we're talking all about why do trees fail? Rob, we saw a post to yours where, in the neighborhood, a tree fell down, right? After a lot of rain.

Rob Dallmann: Yes.

Doug: Let's start there.

Rob: Yes. You mentioned a lot of rain, and that is the case. It did fall down after a lot of rain, but when I consider-- one of the things that I've been saying a lot over the past six years or so is how much rain we got in 2018. It wasn't so much inordinate rain that it's like we've never had that much rain before. In hindsight, it's pretty easy when trees fall down to look at what happened and discern why or try to deduce why.

With this tree in particular, like is a lot of times the case with trees that fail or even when they just die, I have to go back like 25 years to when this neighborhood was built. There's some interesting things about this site. I can see where maybe even farther, longer ago than that, like maybe 100 years or it could have been maybe 60 or 80 years, this area must have been logged because there's a whole lot of tulip trees that all have cavities at the base and are multi-stemmed, which tells me that they most likely generated from root sprouts after they were stumps, when they were logged.

This particular oak, I haven't dissected it yet, but I'm estimating that it's somewhere around 200 years old, it was 60 inches in diameter, massive, and it had a little bit of tip decline that I could see from my house, like across the-- this is a townhome community, and they actually won an award in the late '90s, early 2000s for the way that they preserved nature. There's this joke about how suburbia is where we cut down the trees and name streets after them. We have the name of our street leading in is Woods Landing. Then we're Water's Edge at Woods Landing, so it's like there are a lot of trees here.

I have a stretch of townhomes that is behind me, so we're kind of looking out our back windows at each other, but I can't really see them because there's a strip of trees, so they preserved a lot of trees here. In the process of building, whether they set up tree preservation zones or not, usually trees in close proximity to construction, they suffer some damage. The way that this tree fell over, corresponding with that tip decline up in the upper reaches of the one side of the canopy, all correspond with the root damage that was likely done 25 years ago. Basically, the tree let go on the side where the townhomes are and fell to where it's healthier canopy was.

This was a few weeks ago now. Now all the trees are in full leaf, but when it happened, you could see the buds pushing out and the tree was going to pretty much fully leaf out again, so it was healthy. I don't see any hollow in it really, despite being 200 years old, it certainly has flaws that it's developed over the years because of weather and activity around it and stuff like that, but basically, I would never have condemned that tree or said that it was likely to fail, aside from the fact that it was just a big old tree that had obviously been through some things.

Doug: There are other instances certainly where you can get to a property and look at a tree and say, "Uh-oh."

Rob: Yes. Yes, it's really clear. Even when I'm watching new construction happen and when things occur around trees, then I know, okay, well, I'm going to be watching this over the next couple of years, but more often than not, we're arriving on sites long after construction has occurred, or a lot of times we'll hear, "Oh, well, we did the pool last year or five years ago," and people forget actually about how much wear and tear is done to the soil or around the bases of trees. Certainly, any kind of cavity at the base is a pretty heavy risk factor.

Sometimes things like lean, and then, of course, whether there's wound wood or not and those types of things we look at, storm damage, aside from damage done by human activity, but definitely human activity ranks very high on my list of what is causing trees to ultimately fail, because usually we're dealing with trees that are dying and it could be after construction or just because people have not been mindful of what's going on around the bases of those trees that in the root flare and in the soil system. People forget about the at least one third, maybe even sometimes up to 50% of a tree that is below ground.

They also assume trees, they're made of wood and they're really tough and strong, and "Oh, well that tree got struck by a car on the side of the road and it's still lived for another 30 years, so this string trimmer damage is not going to be a big deal." Of course, a string trimmer or lawnmower over the course of even just a few years, but certainly 10, 15, 20 years will cause substantial damage to the vascular system and base of the tree.

Doug: I guess one thing, one lesson there is to observe what's happening with your trees, right? Probably more importantly, at least in my case, I have to have my arborist out from Davey a couple of times a year. I repeat this over and over again. I live in an oak forest, it's in decline. Yes. I want an expert, and even though I'm the host of this podcast, I'm missing a lot of stuff, Rob. I missed what would have crushed my garage, this giant tree. It was my wife who said, "I can see through that thing." I'm like, "Really? I haven't even looked at it." I right away called the arborist I work with. He came out, looked at it, and started just poking around with just like a knife, and he said, "This has got to come down like tomorrow." [chuckles]

Rob: I've noticed that I think people always, they get busy, they have been involved in various things in their lives. Seems to me like, even since I've been a salesperson and interacting with the public as an arborist over the last 5, 10 years here, I don't know whether it has anything to do with the isolation during COVID or whatever, but people have become more and more niche. They go to work or they work from home, but they're still cemented in front of their computer screens.

Then also, I think a lot of times people-- everybody has interests, but they can defer to the internet, so unless you're interested in nature and in trees, there's not a lot of reason for people to learn stuff about nature, especially as more and more people are moving to cities or suburban areas, and you can Google something. You don't even have to learn species anymore because you can use Google Lens or iNaturalist. Those things, there's a bigger picture there, and when an arborist comes around, they ask you about the history that you know or they'll notice things like, "I'm always looking around for, okay, well, when was that shed put in?" or your neighbors just did something.

We run into all types of interesting things where people will call in and say they think that something happened that we sprayed on their tree, and it might be that their neighbors had their houses power washed and the bleach came over and burned the leaves. There's so many things like that that are happening 24/7 all day long. Anytime we're looking at a tree, it's a snapshot in time where this tree has been standing there for 10, 20, sometimes 50, 60, sometimes hundreds of years, and a lot of stuff has been happening to it.

Of course, trees have a system that's meant to allow them to survive and thrive and generate new growth to survive damage, but they're not always able to, and not only that, but there are plenty of examples of trees that are perfectly healthy as far as their cambium layer goes, their leaves, and the way that they can continue to live, but they're not structurally sound. We encounter that. In fact, my crew was doing a job today where a tree's been damaged by storms a few times.

The tree's vigorous, it's growing beautifully, but actually where it's growing, the stem that's extending up and out is attached to an area where the previous storm damage has led to a cavity, and actually you see sap rotting, decay fungi there on one side, opposite the lean actually. Client wants to maintain the tree as a whole, doesn't want to remove it totally right now, and in that case, we're actually reducing some of the top because we've deemed that the canopy is healthy enough, the tree can survive this wound that we're going to make to it, and that's going to be better for it in the long run because it's not going to be as likely to collapse during a normal wind event.

Doug: I never thought about the kind of history detective that you have to be as an arborist. I'm always thinking like, okay, come on site, you see this is happening right now, and let's take action, but no, you're looking back 5, 10, 20, 100 years into what happened to this tree. What are some other things that we do that we shouldn't that is causing trees to either die or head that direction?

Rob: Like I mentioned, the damage to the roots and the root flare is usually the most common. Second probably, or maybe the only thing that's close to that would be poor pruning. Those are three really basic things, not being careful during construction. Something that is probably less on people's radar is something like the way that development changes the hydrology, the way that the water moves through the soil system.

I have actually seen, going back to that, what I mentioned at the beginning, the 2018, we had 70-some inches of rain in the Maryland area, and that has led to this oak decline. What I also saw during that time was so many trees just die within the next year or two. In some cases, it was like one case in particular where the property was in sort of a low area, and it was full of beautiful white oaks. Up on the hill, like you had to walk around the corner, it wasn't easily noticeable, but around the corner up the hill was some remaining tracks of forest that were being developed into properties, into homes.

Obviously, they removed hundreds of trees that are absorbing and diverting rainwater, but they also put impermeable surfaces in there and put gutters. In Annapolis, we have to have rain gardens and divert water flow that way, but still, even just having like a driveway on the hill instead of a woodland is obviously diverting water and moving it in different ways, so this individual, this property, they lost 12 oak trees, and they were all mature. Some of them were 30, 40 inches in diameter. I saw him two years in a row, where in 2019, they had the first slate and then the second time, so he went from basically having a wooded plot to having just a few remaining trees that were just outside of that floodplain and were able to survive.

Doug: Man, that's a tough thing to have to tell somebody, because in that case, it's nothing he was doing. It was just a change in the area.

Rob: Yes. He also, he did have a shed installed and they drove through this one area. It's not usually just one thing. It's just like with humans or, I compare old trees to-- I try to get people to think of their trees as their pets sometimes, old pets, like old dogs, are you going to have that knee surgery on that old dog when I'm talking with somebody about, "What can we do to save this tree?" or "Is it worth trying to prune it now?" or something along those lines. Yes, a lot of times, it's not any one thing. It's not totally noticeable.

With oak decline right now, we're seeing the culmination really of probably actually a few 100 years of the way that the forest system has been managed on the East. Well, this is a nationwide thing, right? Same deal with forest fires out West. Once the environmental changes happen and you go through moisture extremes, which is what we've been doing here on a yearly level, but even like this season, for instance, when that tree fell down in my neighborhood at the beginning, like maybe a month or so ago, we had just gone through like two weeks where there was hardly a dry day and it was raining for like a day and a half straight, and then it would be cloudy and misty and then it would rain again.

Then now it's been a pretty dry April and we're leading into a dry and pretty hot May so far. When those temperature changes happen on the heels of dramatic moisture swings, that's just all the more stressful for especially mature trees. Again, just like with people, it's the newly planted young ones and it's the old and the battle-tested ones that sometimes they've been through enough and they can't take it.

Doug: Tell me what you're seeing locally when you say oak decline in general.

Rob: Okay. There's a local forester, Bud Grieves, for the county who's been tracking this, and it really, it has been going on for years. A lot of times it has to do, again, with a tree that was damaged, usually it has to do with some kind of construction or things changed around it. A lot of times I'm seeing wounds at the base of these trees that had been there, the wounds have been there for 20 and 30 years. Now that we're seeing these moisture and temperature extremes and the trees also have gotten 20, 30 years older in some cases, they're just not able to keep it up.

Unfortunately, when I think about like the Eastern Forest, for instance, these were really on what I would call our third-generation forest. It was logged by the colonists, and then a couple of hundred years went by or a hundred so years, and then it was logged in the late 1800s, 1900s, and now we're on this third forest, which then that's what we're logging and developing now. Most of these trees are not 200 years old. Most of them are around 100 or so. We know that oak trees can live 1,000 years, and really like 300, 400, 500 should be pretty average for a hardwood and an oak like that.

Obviously, anything that's not living 200 years, there's a reason for that and there's a problem. When I consider nationwide, we've got sudden oak death in California, we've got oak wilt in the center of the country. My family's from Wisconsin. I know we have oak wilt in Wisconsin. I know it's a problem in Texas. Then oak decline in this area. I've heard that it's not as big of an issue in the more northern climes, but you live in Pennsylvania and you're talking about oak decline in your oak forest.

Doug: I'm talking about oak wilt and it's here. The day that my arborist came and picked those leaves up and told me it was oak wilt 10 years ago, 15-- yes, probably 10, I was like, it's a mixed forest, but it's predominantly oaks. I've repeated this a million times on the podcast because it's my personal little situation, but I can't treat all those trees. You lose one a year and you deal with it, and they're good about it. I'm sometimes leaving a-- what do you call it when you leave like a pole?

Rob: A snag?

Doug: Yes.

Rob: Wildlife snag, yes.

Doug: Yes. Just to try and get this done cheaply, I've got four acres of very old mature oaks. That's just the way it is. I've talked also though, everyone I lose, I plant something different. Let's talk a little bit about diversity and how important that is.

Rob: It's extremely important and diversity in species and what we're also getting into now with geneticists and ethnobotany and stuff like that, it's not just species diversity, it's also gene diversity within that specific pool. Over the last 30 years only, we've seen emerald ash borer, now we're seeing beech leaf disease and oak wilt or oak decline, and that's just the last. We can obviously go back to Dutch elm disease and the chestnut blight. We've certainly put our forests through the rigors here and it's amazing that we have as much forest as we do.

It's important that we don't give up on oaks because oaks are a keystone species. For instance, and this might not be exactly correct, but just to use general terms, there's hundreds of butterfly species that rely on oak trees and there's like 10 butterfly species that rely on butterfly bushes, something like that. Beech trees and ash trees and those kings of the forest, when they disappear, it's a huge loss.

I think personally and what I suggest with my clients in this mid-Atlantic region is that they just need to replant, and you can consider, all right, so I lost a white oak, should I plant a willow oak or a southern red oak, which is a more southerly adapted tree? That's something to consider, but then again, we also don't want to only plant willow oaks because then we're going to result in less diversity and we're going to get some kind of blight or some kind of insect outbreak problem like that. I do think some intelligent thought needs to be had around, obviously, right tree, right place, that's basic.

I still see willow oaks planted under power lines for whatever reason. I can't fathom it, but it happens all the time. Whether you're going with a swamp white oak rather than a white oak because it's in a wetter area or you think you're going to get a live oak, which is a more southern tree, I just think really getting something that maybe you move, you plant another white oak, you get it from a southern nursery, could be an option, or you move it a little bit out of that super wet area because things have changed since you took down the other white oak or that tree grew up, so now you need to move it out of the water, the floodplain or whatever.

I think generally, a young tree, once you plant it properly and get it established and it's properly mulched, definitely a pet peeve there, the proper mulching thing, right? If you take care of it and get it established, then it's more likely to thrive and live a long time in this environment because it's going to grow up in that environment. Then the key there is making sure that it's well protected, that you're not hitting it with the string trimmer or the lawnmower and then just creating the same cycle over and over again.

Doug: We talk about it all the time, but I think it's funny when I hear you talk about mulch because it drives us all crazy. We're talking about volcano mulch, we've talked about it 1,000 times on this podcast and it's one of those things that drives you nuts. I'm going to ask this question, I ask it all the time, what's it like when I'm riding in the car with you and you see them volcano mulching?

Rob: I point it out to every customer, I'm like an evangelist, I try to just educate as many people as possible. I joke with people because I think arborists really convinced landscapers to use mulch and then it became like a service line and it became a spring-and-fall cleanup thing that they can sell and then they want to make sure that they give you your money's worth, so you paid for 10 yards of mulch, you're going to get it, whether it's good for your trees or not. That's the thing to me where the mulch is a major headache, but even worse than that is when people will guy or stake trees, anchor them, guy them and then forget about it.

We have these planting projects and they have great themes and they have great catchphrases sometimes and they have great intentions, but if you plant five million trees and four million of them die, great, you planted a million trees, but how many of the-- if you're not maintaining them well, if you're not setting them up for success in the long run, if you can't even come back and take the stakes and the guy wires off of them, you might as well not even plant it because really, it takes more inputs than you're not getting the return, really the measurable return from a tree that's going to die within three or five or seven years.

Doug: You're full of good news.

Rob: [chuckles] I have three young children. I'm an optimist, but I think it's important for people to understand that this is happening. I drive to my office every day and on Highway 100 in Northern Anne Arundel County here, there's beautiful trees in the median strip that was obviously part of some SHA program that they replanted, and a lot of them are doing really well, they look like really nice trees, but they still have their stakes and I'm thinking some of the stakes are falling down and I'm like, "Am I the only one that's noticing this? Am I going to have to stop with my snips and cut them free?" I think maybe I just will.

Doug: I think you just answered your own question because I was going to answer it too, yes, you're going to have to do it. Rob, I think we could talk on this topic for another 30 minutes. Let's save it for next time. That was great information and always appreciate your time.

Rob: Thank you for having me on again. I really appreciate it and it's nice to see you and talk with you again.

Doug: Always great to talk to you. Did you ever lose track of time when a conversation is going so good? That's what it's like when Rob and I explore a topic. It's easy and it's fun. Now, tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I am your host, Doug Oster, and do me a big favor, subscribe to this podcast so you'll never miss a show. If you have an idea for an episode, maybe a comment, send us an email to podcasts@davey.com. That's P-O-D-C-A-S-T-S @ D-A-V-E-Y .com. As always, we like to remind you on the Talking Trees podcast, trees are the answer.

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