 Let's wrap up tonight with a talk about environmental stresses on trees and a number of stresses are showing up now and here to discuss some of the recent symptoms and offer suggestions on how to manage these issues is Dr. Joe's Lesnick. Joe has been with NDSU Extension since 2002 as a forestry specialist. He works throughout North Dakota and in the intersection of prairie and forest in western Minnesota. Joe focuses on tree species diversity in communities as well as he has work on pest management and tree ring analysis. So Joe, welcome to the forums. Tonight I'm going to talk about environmental stresses of trees. So there's a lot of different things we could talk about tonight. I'm actually only going to focus on three drought because while we're coming off of two years, a very bad drought. There's still some question that we might have a little bit of drought issues this year, maybe of course winter issues because it's been a long winter and flooding because now we're getting into flooding. So I'm going to focus on these three items. So first of all with drought, what did we see in the last two years? Of course we saw growth just slowed down. That's what trees do. They compensate internally. If there's not enough water to grow, they won't grow. Yes, they may die and they may have insect and disease issues, but mostly they just slow down. And there is going to be some slower growth in the next year or two because it does take some time to recover from a drought. And like I said, the drought can be associated with specific pests. The two most common are Volsa canker of spruce trees. We used to call that Cytospora canker. The name has been changed and bronze birch borer. And I want to point out here, Volsa canker, what this does, it's a fungus that lives within the tree. And during drought, drought is very associated with this, the fungus becomes more active. It sits in the tree as an endophyte. That is, it's a fungus that lives in the tree without causing any issues at all until the tree gets drought stressed. And when the tree gets drought stressed, this fungus will then form a canker around the base of that branch and it'll kill the branch. It can kill whole trees. This is very common. And the only treatment really is prevention. Yes, you can cut out dead branches, you should cut out dead branches, but the only treatment really is prevention and make sure those spruce trees are properly watered. Spruce are very interesting in that they can't take flooding, but they can't take drought because of the Volsa canker. So keep them properly watered. What is properly? Well, you don't want the roots soaking wet. Put it that way. A good moist soil will be good for spruce trees. The other pest that's very commonly associated with drought stress is bronze birch borer. This is a birch tree in Carrington and the top has all died back. And I went up and I looked at the trunk of the tree and the tree was mostly dead. So I cut the trunk open, cut the bark off it. And here's what I found. I found galleries, tunnels from an insect called bronze birch borer. This is a native insect, North Dakota native insect to the U.S. And it attacks birch trees, especially those white barked birch trees, paper birch trees, and other white barked birch trees. And I found this so interesting, not only were there tunnels, but I could also see where the tree had started to grow over those tunnels. And the tree had started to heal itself following this attack. It was really neat. What I often see from the outside are these types of symptoms. On the right, you see this, excuse me, just getting over cold here. I see this, what I call muscling of the wood. It's kind of a ropey, yeah, ropey muscled look or texture of the branch. The bark itself is still overall, it's pretty smooth. But you get this ropeyness and what's going on there is that's where underneath there, the insects have made those tunnels and the tree is growing over them. On the left, these are the exit holes of the insect. They're the shape of a capital letter D and that's very common because you might have heard of that from the emerald ash borer that hits ash trees. Well, this is a related species, the bronze birch borer that hits birch trees. And again, the biggest treatment here is prevention. How do you know what to do? How do you know if the tree has a valsa canker or bronze birch borer? Do observations, check them out and do your scouting. Treatment is really preventative mostly for bronze birch borer. There are some chemical insecticides that can be used, that can be injected into the stem of the tree. They can be very effective if the tree is not heavily infested. If the tree can take in the chemical from the injections, then the tree, I'll say can be saved. You know, if the tree is not heavily infested, just give it a proper watering can help it out. It can do a world of good for it. Excuse me, and that's all I really want to cover with drought. Not a whole lot there. However, winter issues, and I've got this kind of a broad overview. I call it winter issues here. And, you know, the first slide here, this is animal damage, not really environmental. And those are arborvite trees there on the left. And deer have just hammered those. On the right, it was rabbits that girdled that tree. I think it was a crab apple tree. And yeah, that crab apple tree is dead. I got a question earlier today about rabbits that had girdled a crab apple tree. Was the tree going to die? Yes, it is. On the left, the arborvite, are those going to recover? Well, that's a good question. Where the deer have eaten them, there are no more buds. There are very few buds. And without buds, they're not going to produce new foliage. So there's going to be new foliage above that area and below that area. But in the middle, there's still going to be that gap, mainly. So is that amount that's still alive above that dead area, is that enough to support those trees? You know, I'm not really sure. It looks like very little is left to me. I actually took that photo like 10 years ago. I should go back there and check it out. So winter issues, there can be many. And one thing we commonly talk about is what's called winter injury of conifers. And winter injury is actually a really vague term, because there can be many causes. There can be many symptoms. And basically around this time of year, I've gotten a few calls already, we see just brown needles on trees. Now this is a very specific, special example of winter injury where all those seedlings and there's little saplings there in the front in the foreground, everything above the snowpack has been affected. Everything below the snowpack is still alive. Okay. These are Austrian pine trees and a little nursery on campus many years ago. And those needles that were above the snowpack died. I don't know if it was really sunny. It warmed up. I don't know if it was really windy. I don't know what happened, but they died. Everything below that was killed. That said, all those trees, the buds survived, so they were sending out new growth. So that's just one form of winter injury. Another one, sometimes we see this on spruce trees and there's no pattern to it. Yes, this one shows all of this most recent year's growth is affected. Sometimes it's just the opposite. Sometimes it's last year's growth or the third year growth. Or sometimes it's the bottom of the branches or just the top or just the east side or just the southwest side. It can be very random. And what can you do? Well, not a whole lot because at this point, the damage is already done. So basically you just got to wait it out and let the tree grow out of it or it won't. With my own tree that suffers this every few years, my own ponderosa pine. Yes, it gets damaged in years where there's a highly variable spring temperatures. And so we see an issue then. And it just grows out of it over time. So hang in there. One thing we saw a lot of this year was just playing physical damage from the snow. And this was a little different. Excuse me. We had a lot of snow and a lot of it was wet, heavy snow. And what happens here? This is my own ponderosa pine tree in my yard and that top leader is just bent right over. What can you do? Well, what I ended up doing is I got a big, big long pole and knocked off that snow. Got the weight off. And you know what? It started to straighten itself up. And I'm going to be very curious to see what happens this year. So what can you do if you really want to do something? You can splint the top of a tree. Now this is, I believe it was a hackberry tree. But you can splint the top of a tree. You can do this with a conifer or anything else to get one main leader. And you just get a big, long bamboo pole and get some cloth strips and tie them up along the stem and tie that leader onto it. And that can help to straighten it out. You might need to leave it on there for a year, maybe two, but no longer than that. Take off that splint over time. And I could do that to my tree, but I'm choosing to not do it. And I'm going to see if it's going to come back straight or if it's going to have a little curve along the stem. It's going to be interesting. Now if the top was broken, well, really then the only thing we could do is prune it back and let one of the side branches take over as a leader. And then we could train that branch into more of a central leader as best we can. We also saw a lot of this. These are arborvites, but also junipers were showing this, especially these upright cultivars where there's not just one central stem. There's several and they just kind of peeled open like an onion. What do you do? What do you do? And really, each situation is unique. Sometimes you can do nothing and they'll be fine. Sometimes the best thing is to get rid of them, unfortunately. So each situation is different. I will say this. If branches are broken, remove them and use some proper pruning techniques. There should be no topping of trees, especially these conifers because they're not going to come back if they get topped. The other thing is you can draw those branches or stems back together. And I will say this. If you use a rope, use it to draw them back together, but really what we want to do is strap them together. And don't put the rope directly on the stem. Use the rope to draw the straps together because the straps provide support and we're cushioning the stem. We're not going to rub against the stem. Although I will say that bungee cords might be okay because they flex. They provide some support, but they will also flex. But I want to point out in terms of drawing these stems back together, this is going to be a long-term situation that you need to do this for at least a year or two. And maybe even three or four years before that stem has built up enough strength, enough new wood before it can support itself. So something to consider there. So that's the physical damage. There's no guarantees on if this will work or not. Each situation is unique. And do nothing is always an option. Something to consider. One thing you may see, I want to point out here is something called frost cracks. These are cracks that form along the stem of a tree. Usually it's a deciduous tree. I don't know that I've really seen this much on conifers, if at all. And sometimes it's on the southwest side. This one is actually on the east side of the tree. This is an ash tree in the city of Dilworth, Minnesota. And this one is huge. It goes all the way from the bottom of the tree 15 feet up. And what happens here is during extremely cold weather, and when I say extremely cold, we're getting down to 25 to 35 below. Sometimes the stem will just pop open. It'll just break right open. It'll sound like a gunshot. And that tree just cracks. And what happens? This is the southwest side of the tree. And you can see there's a break over here as well. What happens? Physically, we're still trying to figure it out all these years later. It could be that the stem shrinks and breaks. It could be that the stem swells and breaks. Regardless, this is what happens. And do these cracks grow over? Do they heal themselves? Sometimes yes, sometimes no. Sometimes they will grow over. The tissue will heal back together. And you'll get a frost rib. And sometimes it just keeps opening and closing every winter. So it's really variable. I've seen these on cherry trees, birch trees, aspen trees, ash trees, maple trees, a lot of different deciduous trees. This happens. Really, there's nothing we can do except wait it out. Unfortunately, sometimes these are entry places for the fungi that will decay the tree. So some of the pests. So that's unfortunate, but it does happen. So very briefly, there's a little bit of winter injury. Let's get ready for flooding now because that's going to happen. Very likely, what's the prediction? Well, let's see. In central North Dakota, here are the predictions. Chances of greater than 50% chance of moderate flooding is in red. Greater than 50% chance of minor flooding is in orange. Okay, it's a little bit mixed. Less than 50% chance of flooding is green. Okay, so it's a little bit mixed bag in central North Dakota and along the Soros River, central and north. In eastern North Dakota, yeah, it's a little more clear that it's going to be either some moderate to major flooding this year. Greater than 50% chance. Of course, it depends on how fast the snow melts and we'll see what happens. But what does this mean for the trees? Well, tolerance to flooding really depends on a bunch of different factors. Specifically, the timing of the flood and the duration of the flood. So this is an example from the Red River, 2010 in March. What do you see on those trees? Anything? No. No, they're dormant. The trees are dormant. It was actually really early in 2010. Actually, 2009 was even earlier at the end of February or mid-March, rather. So how about if it floods in June and all those trees are in leaf? That makes a little bit of a difference there. So that's something to consider. So what really that means is are the trees dormant or not? If trees are dormant, quite frankly, they'll do fine. Conifers generally can't handle flooding. Especially those spruce trees, Arborvitee are a little different. They can actually handle a little bit of flooding. They are a swamp species. But the spruce trees, the pine trees, they cannot handle flooding unless they're dormant. If they're dormant, it's not a big deal. If you go to Minot these days and look in that area that was flooded in 2011, look to see how many conifers you find in those neighborhoods. You're not going to find many because that flood happened in mid-summer and those trees were not dormant and they died pretty quickly. So a part of this and then is also related to species. This was 2011 in Bismarck. And this was... Megan Miradol was the county agent back then. She took these photos. I'm trying to remember if these were junipers or if these were Arborvites. I can't remember for sure. But again, in 2011, from the areas that were flooded in 2011 in Bismarck, you're not going to find many conifers there anymore. When I went back to this area in 2012, this is the Fox Island area of Bismarck. So it's kind of south of the golf course, south of the zoo. This was interesting to see that a lot of the Russian olive got knocked back because it was flooded in 2011, yet the cottonwood trees were fine. So it can be species dependent and the cottonwood trees not only were fine, this was with a couple feet of sediment on the soil. It was pretty amazing what we saw after that flood. So if you want some more information about flooding and trees, we do have a publication helping flooding trees and shrubs. Very briefly, it talks about some of the symptoms and what are some of the recovery actions that you can do to take care of trees after flooding. And there are some tables on the back page of this with both trees and shrubs. And there are different abilities to tolerate or inability to tolerate flooding. So if you have more questions, look for what was it? H1592. All right. So one other thing I want to point out here is the weather afterwards. This was also an issue following the 2011 floods in Bismarck. Waterlogged soil and then there were big windstorms and trees got knocked over left and right. And this was really sad. And was there anything people could do? No, not really. So what we can just do is be aware that this could be an issue. Soil's waterlogged and then we get big, heavy winds afterwards. Be careful. Be careful. This is going to be a problem. And I think actually that's all I have tonight. It's actually a very quick little coverage of just a few of the major environmental stresses. Of course, there are much more. We could talk about winter de-hardening, which we saw on birch trees back in 2021, where we get these really variable temperatures in the spring. We could talk about early frost or late frost, excess heat, soil issues. There's a lot the mother nature throws at the trees and we could go for a long, long time. But with that, I'm going to set this aside and see what kind of questions there are. Okay. Joe, there's a question about the frost cracks. Do both younger and older trees suffer from frost cracks? You know, I've usually seen them on trees that are bigger, older. I would say maybe 10 to 12 inches diameter and bigger. I don't know that I've really seen them on smaller trees. Okay. How about this person's young junipers are completely covered by snow? What can they expect? Well, it depends on a lot of different things. Are these shrub junipers? Are they tree junipers? If they're covered by snow, is it a heavy wet snow? Is it a light snow? There's a lot of different things that could be going on. That said, if it's just they're simply covered and there's no other issues, well, they grow out of it. It'll warm up, the snow will melt, and they'll grow just fine. They should. Okay. Got more information on those junipers. They're a classic sea green juniper. I'm trying to remember. I've heard of that cultivar. I'm trying to remember if it's a tree or a shrub. It's a shrub. It's kind of a shrub. It's foundation planting. Yeah. Physically, the weight of the snow could knock that down, crush it a little bit. But generally, they should be fine. Okay. This person has a William Baffin rose bush and the rabbit at the top of it. Do you think the plant will survive? I have no idea about roses. I, how long, my guess would be it would depend on how long it's been established. And if it does have a good root system established, whether or not it will come back. Yeah, that William Baffin is a tough explorer rose, very hearty rose. And it should come back from, it looks like they didn't, the snow protected the lower portion. Sure. So it looks like just kind of what you showed there, Joe, with that tree that was at a crab apple or an apple tree that got totally filled around the, it's just kind of like that kind of situation that everything that's going to eventually die off. Right. Okay. Well, let's see here. Here we go. There's a west facing shelter belt filled with snow from November till now. The 15 foot junipers and the spruce are leaning. And now with the melting snow, the branches are snapping off. Would you start pruning the injured branches? If you can get to them. Sure. If you can get to them, prune them back to a, to where there's a connecting point with the main stem or previous branch. If, if you can't, you know, they could probably wait till next fall before you prune. But yeah, get in there, prune those out as best you can. This person has a two year old silver maple. It budded. Then there was a cold snap and it didn't get many leaves. Yep. Now last year they got more leaves and there were some insects on the trunk. Any idea about the future of this young silver maple? Well, when it survived, it had just a few leaves last year. Just a few leaves. You know, the tree needs a lot of leaves to survive. I am very curious the, going first, I'll do the insects because that's actually pretty easy. There are so many insects around here that hit so many trees. Usually they're not a big problem. You know, if we're talking on the leaves of silver maple, what I'm wondering if those are like a bladder gall mite or a spindle gall, you know, without seeing the leaf. I'm something I usually don't worry about. That said, trees need the leaves to survive. And if they're getting damaged by a late spring frost and, and or like you said, they, they budded out early. That's one thing. One thing that silver maples tend to do is they will still start to grow leaves early and then it gets cold again. It's not really a frost per se. It's that they break dormancy really early. And that's really hard on trees growing in the Northern Plains. They need to stay dormant for longer. And that's one of the challenges. I know that Dr. West has and anybody that's selecting trees for, for release here in the Northern Plains is the trees have to stay dormant. So back in 2021, what we saw throughout most of North Dakota is a lot of the birch trees had their tops died back. This was Dakota Pinnacle, Parkland Pillar, some of the Asian white birch, some of the European white birch, the weeping white, European white birch, their tops all died back. What we traced that back to was a warm spell we had in February. The trees de-hardened and once it got cold again, they couldn't re-harden. This happened throughout the state. So that may have happened to the silver maple and it's going to need a couple years to recover if it does recover. Joe, do you have kind of a general rule about like defoliation of trees and shrubs? Like if they get defoliated one year, can they survive? Can they survive after defoliation two years? Sure. Okay. It's a general rule of thumb. If a tree is otherwise healthy, I'm going to start it out with that. If the tree is otherwise healthy, it can handle and is, well, let me back up. If a deciduous tree is otherwise healthy and it gets defoliated in one year, maybe there's either a late spring frost or we get like canker worm infestation, which can also defoliate trees. Yeah, one year, not a big deal. It can handle it. It will send out new leaves. The crown might be thinner for that year, but it should recover just fine. I remember seeing an elm tree in my neighbor's yard one year after a spring frost. It was very thin that year. That crown was thin. The following year, it was fine. It was a nice thick full crown again. Okay. If a tree is otherwise healthy, it might be able to take that two years in a row. But once you start getting to a third year, boy, that's a big stress on the tree. And like I said, I'm going to give a big caveat there if the tree is otherwise healthy, because there's a lot of different things that can hit trees. Yeah, that's good. How about, Joe, you talked about drought. Can you recommend shrubs that will tolerate dry soil? Oh, geez, the junipers or what come to mind off the top of my head. I don't often think about drought-tolerant shrubs. I believe it's funny earlier with Todd, a question came up about sand cherry. Sand cherry can handle that kind of environment. And I'd say if you go to Western North Dakota and look at some of the native shrubs out there, you're going to find a lot of very drought-tolerant species. They're tough. They don't tell us native. Yes. That's a pretty tough one. How about a mugo pine shrub, 25 years old, the rabbits chewed on, but then they screened in the area and the rabbits didn't get to it after that. So the screen area, they didn't get to be in the area last. So the shrubs have been okay for a couple of years. So it sounds like it's going to make it. Sure. How about a four-foot juniper tree the leader died off during winter? They trimmed it off. Is there a way to reshape it or create a second leader? Basically, I'd say wait to see what the tree does to start to create a new leader and then make your decisions. If there's one branch that's coming up and you want to encourage that, yes, you can turn it upright and splint it like I showed in that one photo. If there are multiple leaders, multiple branches that come up to become competing leaders, then you may have to make some decisions on which ones to trim and which one or maybe two to keep. So I'd say first observe and then make your decisions. So this person has a boulevard tree. They just planted it in late September and Bismarck. And they're just wondering like, what should they be looking for to make sure that it's doing well? And should they be watering it on a regular basis? For example, using those tree bags, those data bags? I'd say wait and see what nature gives for moisture. If you're getting an inch a week or two inches in two weeks, that tree should be fine. But wait and see. And I wouldn't give it more than an inch a week. Depending on the size, as a rough rule of thumb, a one inch diameter tree, one inch diameter stem, that tree can use three gallons of water a day in the summer. A two inch diameter would go for six gallons of water a day. I wouldn't water it every day. I'd water it once a week or maybe once every two weeks. And just soak it in, soak that water in and let the tree slowly take it up. And if you're wondering about the soil moisture, you can use a screwdriver stick in the ground just to feel the soil, whether it's dry or moist or wet. If it's wet, don't water. If it's moist, don't water. If it's dry, water. Okay, Joe, this person's got an autumn blaze maple. 24 years old, it says. And it's got cracks in the trunk. They've wrapped the trunk and it seems to be recuperating. But now the leaves seem to be more yellowish green in the summer. So should they give a tree a shot of something? Yeah, autumn blaze is not the greatest tree to grow in North Dakota. I'm surprised you've had one survive for 24 years. Excuse me. Autumn blaze is very sensitive to iron chlorosis under high pH soils. We have plenty of iron in the soil, but it's just not available as well. And autumn blaze maple, some of the silver maples, as well as red maple, which is one of the parents of autumn blaze, are all sensitive to iron chlorosis. So if a tree is showing symptoms, then yes, it should be treated with some type of iron treatment. We have a publication on iron chlorosis. I don't have the number off the top of my head. But if you look for NDSU extension, iron chlorosis in trees. We have some great information there on how to treat it. There are soil treatments, there are foliar treatments, as well as stem injections that can help the tree. Okay. Joe, this person has a question about, we're back on William Baff and Rose again now. And they've got, what's the best spray for pests? So if someone gives you that question, what's your answer? What's the best spray for pests? I'd say that's a, my answer would be, you have to be very specific about which pests. And there's their fungal pests, their insect pests, and there are animal pests too. So I would say scout, observe and learn what the pests are and then treat them. You got to know your enemy for your attack. How about, Joe, you know, there's an old saying that under a conifer, you can't grow anything underneath it because it's acidic soil. But other people say that it takes hundreds of years for the soil to change. And the biggest, the problem underneath the conifer is there's not enough light or water. So, but spruce can't take flooding. Right. So where's the balance in all this? And is there any truth in that acidity of the soil is killing off all those undergrowth? The acidity to change substantially does take hundreds of years that, you know, maybe in a thin layer, a quarter of an inch thick, there might be a change in acidity under a tree in one generation. But that's it. You really to do any substantial change in the soil acidity would take hundreds of years. It is more of an issue with light and light availability. If you want to grow something under a conifer, yeah, good luck. You get something that shade tolerant. Actually, my wife and I are trying this right now. We planted some hostas. She wants to try hostas underneath the spruce trees out front. So we'll give it a shot. And I do have to give them a little extra water. Okay, we'll just end on this. There's this person has several mature black kill spruce that are leaning due to high winds. So these are mature trees. So now should they pull them back to be to straighten them out? You know, this is a this is a tough question. There's no easy answer here. If they've if the root system has actually popped a little bit. It's going to be tough for those things to survive, but they might it's really your choice whether or not to do it. You can either push them back up straight. You can pull them back up straight or some combination. But you're going to need to provide that support for several years while the roots reestablish and the stem reestablish reestablishes its strength. Or you can leave them leaning and from that point forward, then they'll go straight up. There's a beautiful old blue spruce tree on the grounds of the Wilson Research Extension Center. And one of the houses there that's looks like this for about 20 feet. And then the next 30 or 40 feet are straight up. That tree got tipped many, many years ago, and then it grew straight from that point forward. So it's really your call. Yeah, that's called character. Just like that beard of yours, Joe, it's character character. It's character leaning trees, just adding a little character to the tree. It doesn't have to be straight and perfect. It's not it's got no character. Joe, thank you for your presentation tonight. We really enjoyed it. You're very welcome. Thank you for having me. Oh, sure. Always welcome, Joe. Okay, that's it for tonight. That's it for our spring fever garden forums for this year. Again, I will shortly send an email to the at home registrants with a link to do a short survey. We'll keep that survey open for a couple of weeks. And I really would appreciate any input from you and assume at the county offices if you could complete that form. That would also be appreciated. So there you go. It feels like finally spring has arrived. And so now that spring is here and as we head into the summer, please know that NDSU extension is here to help you. If there's have any questions about caring for your landscapes or your gardens, please let us know. So everybody have a good night and a happy spring to all.