How Extreme Weather Affects Trees

Dan Blazer from Davey’s Southwest Milwaukee office talks about extreme weather’s impact on trees and the best practices for caring for them.  

In this episode we cover:  

• Temperature changes and extreme weather (2:55)  
• Watering before winter (7:15)  
• Basics of mulching (9:48)  
• Fertilization and extreme weather (11:54)  
• Extreme weather’s impact on trees (13:33)  
• Planting with the changing weather (15:35)  
• Other considerations for homeowners (17:16)  
• Tree planting diversity (19:20)  
• Dan’s passion for his job (23:20)  

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

To learn more about protecting trees from the winter weather, read our blog, Protecting Newly Planted Trees from Frost & Cold Winter Weather.  

To learn more about proper mulching techniques, read our blog, The Proper Way To Mulch Your Trees.  

To learn more about winter hardiness zones, read our blog, Climate Change Projections: The Impact & Why You Should Care.  

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

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

Transcript

[music]

Doug Oster: Welcome to the Davy 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 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 Dan Blazer. He's a consulting arborist in New Berlin, Wisconsin for the Davy Tree Expert Company, and we've been having a lot of fun going round and round with the technical aspects of doing a podcast. Dan, we can hear each other. [chuckles]

Dan Blazer: We're here.

Doug: This is exciting. We're talking all about weather extremes and what that means for trees. When we say that, what is the first thing that comes to mind for you?

Dan: Good morning, Doug. How's the weather over by you today?

Doug: We're lucky. We've got some rain. I know you guys haven't had rain in, what, 10 days?

Dan: Yes, at least. There's plenty of moisture in the soil now, but I'd like to see some rain in the next week.

Doug: It's always a concern for, and I say this all the time, but anybody who grows anything, when it's not rain it stinks, man. I'm telling you. Every area is different, and I feel very lucky here in these hot summer days to get a little bit of rain just to keep things going. I'm still watering containers and such, but my trees in general, especially my newly planted trees from last fall, I feel pretty good about it.

Dan: Thinking about the year 2021, this is still early yet this year, but we had plenty of rain, but it all came in big dumps earlier in the summer, and then we had a huge drought. September-October is the driest I ever remember.

Doug: Yes. That's the hardest thing. Especially when you're talking about trees. You got to go keep your trees watered, and they take a lot of water. Especially if you've got a decent-sized tree, one-year-old, two-year-old, you got to go soak them in.

Dan: Yes. Especially newly establishing trees. They're getting full sun underneath the canopy. They're not really self-shading yet like trees are in the woods, so evaporation, is-- How much is evaporating out from underneath the tree is equally as important as watering because they're-- The water is always evaporating but if you just water them once a week, five gallons can evaporate in one day if it's full sun underneath the tree canopy.

Doug: I'm sure it's not just water we're talking about, when it rains and when it doesn't, but also temperature changes, right, as far as when we're thinking of our trees?

Dan: Oh, yes, absolutely. Weather extremes. It's been an interesting last decade. In the last decade, we've seen just about everything. We've seen polar-- The "polar vortexes". I know in the wintertime I'm not-- Really recall what years they were. I think 2011 going into 2012 was one of the most noteworthy.

Doug: Yes. That polar vortex did a number on us here. As the planting zones have changed and every how often they do it, I don't know how often they do it, but they put a new zone map in and they call an area like ours Zone 6, and we start planting plants that they tell us Zone 6. Then polar vortex comes and forget Zone 6 plants in many cases. Leland Cypress took a bad hit here. Lots of other plants too and so it's pretty crazy. What else have you seen as far as, where you're at, as far as these-- This extreme weather?

Dan: In addition to like the rain falling in larger dumps followed by longer droughts, I think we've had fairly mild winters in the last few years as far as extreme temperatures are concerned. That's what the hardiness scale tells you, how many frost-free days that there is. I think there's more to it than that. The freeze-thaw cycle. More days in February, in late February and early March, or even into April, that are in the forties during the day, and it's still freezing at night.

You can't really change the sun and the position of the earth. That's always going to be about the same. You're still having dark nights, long nights and the temperature has to go down. At nighttime, it's like being in outer space. As long as the sun's not shining, it's getting colder and colder. We're still seeing those cold nights, but we're seeing more insolation, which is insolation, incoming sun radiation, that heats up the earth where things are getting warmer.

That's that cycle of freeze thaw that I'm most interested in, and I think has more to do with killing off plants, freezing tree roots. The first thing comes to mind, Japanese maple, London planetree and tulip tree are three trees that we've been utilizing more here in Southeast Wisconsin as a replacement for all these ash trees that we've been removing. Sweet gum is another one we're talking about using some more. A lot of East Coast trees. We're still having trouble with them.

I think it's got to do with still having a lot of cold at night. Then the daytime temperature is rising and that freeze-thaw, even though they can survive in a "Zone 5", we still have that freeze-thaw cycle for such a long period of time, and I think that does a lot of damage to root tissue and to soft, twig tissue. It's like a freezer. It's like a deep freezer. Freezes everything solid, and it doesn't go through a thaw cycle, and it stays deeply frozen. A freezer that is like a frost-free freezer that goes through a defrost cycle.

You'll notice like your bag of vegetables has all that frost and then the vegetables, they get freeze-dried. What happens when it thaws and freezes and thaws is the moisture goes from-- It goes from the tissue into the air pockets, so that there is a good reason to water late in fall. Keep your trees watered, especially if it's dry because you want your trees to go into winter with plenty of moisture to get through all that freeze-thaw cycle that goes on, both up and in the ground.

Doug: That is a great point and something that we're always telling homeowners. Again, is this more important with newly planted trees as far as that watering until the ground freezes or is it all trees we're talking about watering before the ground freezes?

Dan: Most, especially newer trees. If the tree is younger than 10 years, and it's getting established, it's always going to be more true. We lost a lot of trees that we planted in 2021 and that they just didn't seem to come back. Especially conifers, especially a lot of spruce, Norway spruce, that were planted in 2021. They made it through the summer, they made it into the fall, and they even went into winter. Green, just fine.

Then come April-May, they were starting to just drop leaves and turn brown. It's just crazy because we've just never seen anything like that. It had to do with the really dry fall we had. September, October, November, people are getting into a different mode and they're like, okay, we watered these trees all summer, they should be fine.

Doug: Let's talk a little bit about that, especially with conifers. We plant a conifer in the fall, be sure it's watered. Then is mulch the same thing, proper mulching? Is that going to help?

Dan: Absolutely. Mulch reduces evaporation, keeps the temperature more consistent over the root zone, which is really important. It even encourages insect activity to move from the soil into the mulch upward and downward, and it eliminates that hard pan that you'll see over bare ground. Because certain insects, they don't want to come above ground, they want to stay in the ground, so mulch is a great barrier to regulate soil aeration.

Doug: We talk a lot about mulch on the podcast. I don't want to sound like a broken record, but if you could just talk a little bit about the basics of mulch. Not to volcano mulch, how thick it should be, and where the mulch should be, please.

Dan: When you first plant a tree, you're going to want at least three to four inches of mulch over the root zone, preferably out to the drip edge which would be the outer branches where they trace a line straight downward. I put it a little bit thicker at first because that does-- It does settle. You put four or even five inches down and you come back even a month or two later, and it's going to be two inches to two and a half inches thick. It's amazing how quickly mulch does break down, especially that first application when you install mulch.

It's also a really important follow-up mulch planting a new tree. Say you plant a new tree in the spring, you're going to want to mulch it again by September or August. Just mulch that's in contact with the soil, initially, it breaks down quicker. Out to the drip canopy and, of course, keep it away from the root collar and from the trunk. Root flare and trunk tissue is not designed to be in contact with moisture, so it's really important to plant trees at the proper level. Proper level being almost always two inches above surrounding grade, possibly more.

Also remember, tree root balls, they plant trees deep in nursery fields so that they don't topple over. Container-grown trees are almost always going to be-- The root flare is going to be, possibly, a couple inches up to two-three inches beneath the surface of the soil. That's the level. The root flare needs to be above the surrounding grade. Not the top of the soil that comes with the container or the root ball, but you need to find that root flare and make sure that that's above grade.

Doug: I'm so glad you brought that up because I had no idea. I'd heard that, yes, if you get balled and burlap, that you've got to pull that off and find that root flare, but I wasn't aware that when you buy a container tree, until I saw a Davey arborist plant one, that I had to do it there too. That's great information. Does fertilization come into this at all for extreme weather or not?

Dan: Well, the way I always explain that is talking to your doctor about taking a vitamin and eating a healthy diet. The answer's always going to be yes, of course. Quality fertilizers like what we use, Arbor Green Pro, our in-house made fertilizer is really good. It's slow-release, a very low salt content, so you don't have to worry about burning it, and it'll only be released if it's needed.

Doug: Oh, I like that.

Dan: Yes, it's slow release. It'll interact with microbes in the ground, and it'll only release enough that is needed, so it's really hard to overdo it. It's nice to have that reassurance because that's the number one concern of fertilizing is actually overdoing it, but we don't have to worry about that. Yes, it most definitely can only really help. Even newly planted trees.

Doug: Is that something we do now or do we do it in the spring or both?

Dan: Of a lot of the things we do, it's probably the least time-sensitive. There's so many things that we struggle to get done in a time window. Pest control, disease applications are very time-specific, but fertilizations are something that can be done literally anytime throughout the year, but we tend to do them in spring and in late fall.

Doug: Okay. What are the other things, what are the other problems with our trees that you see during these-- This extreme weather changes that we've been dealing with, certainly, at least for the last decade?

Dan: It's interesting how everything is related and weather, most certainly is the leader of the pack for the things that can follow. Insect, insects' metabolism are strictly dependent on what-- On temperature, so when it's medium temperature, you see an ant hill and they're moving slow but if it's a hundred degrees, they're moving so fast, you can barely see them. That's basically the same with every insect. Their metabolisms are dictated by temperature.

Possibly, increases in temperatures, longer, warmer growing season is going to create a more inviting environment for insect. More moisture, of course, is always going to possibly mean more fungi. Both of those things can put stresses on trees, and when trees get stressed out, I don't know how the phenomenon works, but stuff knows. It knows to take advantage of things that are under stress.

Both insects and fungi. Even fire blight, which is a bacteria, seems to be stress-related. More moisture in spring. We've been seeing more root rot. At least maybe I haven't noticed as much in the past. It could be just my observation. It's funny how that works, but root rot on, especially, sugar maple. Lots of armillaria root rot which is a-- Probably the most common type of root rot in maples.

Doug: Does it change? Do these weather conditions that you've seen, does it change your decision on what to plant where?

Dan: Yes. Quite honestly, the soil conditions where you're going to plant something is the first thing. Then the second thing is the location, the preposition. Shade, the amount of sun is another consideration, and space. I see so many trees that are actually overplanted, that are planted too close. Remember silver maples, you see them planted 10, 20 feet apart. Spruce trees, when they're six feet tall, they look great when they're 10 feet apart, but on down the road, they're overplanted.

I really try hard when I'm planting not to overplant. I'll be honest, I still wind up doing it. [laughter] It's like in 25 years, yes, those trees are going to be touching. Maybe we could've-- It's done with the best intentions. Planting depth. We see so many trees that are planted too deep, and it's like they didn't intend on that. It's just constant mindfulness of what you're doing and trying to do it right.

Doug: It is best intentions, and I feel your pain there because I'm the same way. I know where it should be and how much space it takes and everything, but every once in a while, you get 5, 6, 10 years down the road and you're like, "Oh, I guess I should have given it a little bit more room. I should have known better." When you're thinking of extreme weather and our trees, is there anything else homeowners should think about in their own landscape to get through this, to make the plants-- The trees happier?

Dan: Absolutely. The first thing that comes to mind is diversity. If you're speaking from the planning phase on forward, let's just say you're starting with a blank sheet of paper-blank property, diversity, diversity, diversity. That's the only thing that can-- That's probably going to get you through. I don't have a crystal ball, I don't know what the next big thing is going to be, and no one can know what the next big disease, insect, anything, nobody can know what that is, but having a diversity is the only thing that can really give you the best chance.

I'm seeing that lacking in a lot of landscapes, a lot of newer landscapes. I'm seeing four to five different types of trees and shrubs. Well, four to five different types of trees and that's about it. It's kind of disappointing. Municipalities are-- That's not really the case. Urban trees that are planted by the cities, counties, they're doing a pretty good job with diversity. That's the leader. They lead the way.

They're planting street trees, they're using a good variety, but on the landscaping side, everybody wants that nice bright red maple. I'm driving down the road, I'm seeing autumn fantasy maple, autumn blaze maple, freeman maple, or a bunch of different types of crab apple. Maybe some flowering Bradford or the calorie type of pears. To be hon-- I don't like those trees very much. [chuckling] They're troublesome.

Doug: All right, go deep into your tree list. I always preface this with right tree for the right place, but tell me a couple things, when we talk about diversity, that you would love to see planted out there that really aren't planted as much as they should. I was at a property yesterday. Again, HOA, Home Owner's Association, is dictating what can be planted. You're exactly right. You drive through that neighborhood, five trees. That's it. They're blue spruce, flowering pear, hemlock, and I forget the other two, but everybody had the same ones. Let's mix it up a little bit. What would you like to see planted as long as we had the right place for it?

Dan: That's a good question. I'm liking Kentucky coffee trees.

Doug: Oh, yes, talk about that. That is a cool tree.

Dan: A lot of people go, well do they get the big pods? There's a variety that does not get the pods, called the expresso I believe. [chuckling] It's a Kentucky coffee tree, seedless, so don't worry about the big taco-sized pods that they get. Not super stunning at first. They look kind of like a broomstick with two branches coming out of them but give them a chance. They're late to leaf out. Some people see them in 1st of June and go, "Where's my leaves?" They really do, once established, they can take salt, they can take heat, they don't grow too fast. They're one of our favorites.

Dan: When I see a mature one I just am like, that's a great tree, and then, why can't we have more of those. We do not see too many mature ones around here yet. Kentucky coffeetree. I like London planetree. However, there was a hiccup with them with the hardiness thing. Honestly, it wasn't that cold of a winter about five or so years ago. Nothing really noteworthy about how cold the winter was. Suddenly these things were-- Died back, and they were suckering from the trunk.

Something related to weather. What? We don't exactly know. These are locally grown trees, so they are raised here. These were not shipped in and planted and then they had the problem. They grew here for five to ten years. All of a sudden, one year, they had an issue with hardiness. London planetree, I feel good about it, but that one year was kind of a hiccup. Tulip trees, a huge staple on your East Coast areas. Very few and far between here in southeast Wisconsin.

I might go an entire couple weeks and not see one tree, but they are being used more. Our local nursery had trouble with those this last winter. We think it may be weather-related. How does our weather here differ from other Zone 5 East Coast areas even though we may be in the same hardiness zone, and they've got trees that they have no trouble with that we have trouble with even though we're in the same hardiness zone.

Well, what's the deal there? Well, there's certain things that can't be fully measured by just the hardiness zone scale. I think it's related to those-- The freeze-thaw cycle possibly. We have a lot of cold days here still, and that's not changing. What does change is those late winter days that get above freezing. We're still getting cold at night, and we're getting above freezing, and I think that freeze-thaw cycle is what causes some of the problems. That's not really a secret. A lot of my colleagues that I've talked with agree with me on that.

Doug: Well Dan, before I let you go, just tell me what you get out of doing all this. About studying this and in working with people to try and make that landscape more successful. What do you personally get out of it?

Dan: Fascination. It's fascinating. I love it, and it's rewarding. It takes time to become rewarding because in this what we're speaking of specifically, planting and trees, are the trees that I've planted over a decade ago that I get to go back and visit and climb. There's a lot of trees that we're climbing and pruning now that we planted. That right there was something that I like the most about my job.

Being able to help and develop a relationship through trees, to have a conversation piece when you go back to visit a client, and they got their 25-foot-tall katsura tree or-- That we're climbing to prune now, that's really cool. Even though they doubted me at first for the first five years. [laughter] You're, just hang in there. Keep trying, keep working hard, and buy local. Buy local nursery stock.

There, well, no matter where you are in the country, you can find a local a local nursery. By local it might be a hundred miles or 150 miles or something, but you can do it. We're lucky enough to have a really great-- A great industry leader right here about 10 minutes from our shop. We also have our own nursery in Ohio, and they have some of the best-looking trees I've ever seen. The training pruning they do on them, some of these trees arrived and I was like, "Wow, is that a beautiful tree."

Doug: I'm going to leave it right there with the "wow". [laughter]

Dan: Oh, that's good.

Doug: Good stuff, great information, and fascinating. I'm sure for the listeners because it was fascinating for me. Dan, I'm glad we finally got this going, got our technical problems taken care of, and I enjoyed talking to you. I'm sure we'll talk again. Thank you so much.

Dan: Sounds good. Take care, Doug.

Doug: Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host Doug Oster. Next week, you're in for a treat as I'm reunited with my old friend Todd Sherbondy who will talk all about why your trees might be losing their leaves now and into the early part of fall. Do me a favor. Subscribe to the podcast so you'll never miss a show. As always, we like to remind you on the Talking Trees podcast, trees are the answer

[00:26:30] [END OF AUDIO]