Hawthorns: The Different Types + Common Diseases

Lou Meyer from Davey's mid-Atlantic region shares information about green and Washington hawthorn trees, including what diseases they are susceptible to and how you can diversify your landscape by planting them. 

In this episode we cover:  

• What are hawthorn trees? (:43)
• Does Lou see fire blight on hawthorns, and can it be controlled? (4:49) (5:14)
• How hard is rust to control on hawthorns? (5:51)
• What are green hawthorns? (7:02) (7:56)
• What are Washington hawthorns? (10:44)
• Are hawthorns common in mid-Atlantic landscapes? (13:56)
• The importance of educating clients about new species to add to their landscape (14:48)

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

Listen to this Talking Trees Podcast episode, Importance of Diversity in the Landscape and Planting to Replace, to learn more about diversifying your landscape. 

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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

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.

Our friend, Lou Meyer, is back. He's been on the show more than just about anybody. He is a regional business developer for the Mid-Atlantic region for the Davey Tree Expert Company. He is based in Baltimore. Today, we're talking about a tree that I know nothing about. This is part of our series on specific species of trees. Lou, I don't know anything about hawthorn trees. I don't even know if I would know what it would look like.

Lou Meyer: Let's dig into it, then. Yes, the hawthorns are part of the Crataegus genus. They're part of the Rosaceae family. This is the rose family. There's about 5,000 species, including apples, pears, plums, cherries, blackberries, strawberries, almonds, and others in that Rosaceae family. There's a lot of different types of hawthorns out there. Today, we're going to talk about two specific species, the green hawthorn and the Washington hawthorn. Backing up to the family itself, or to the genus hawthorn, Crataegus itself, they're smaller trees. They get 25 to 30 feet tall. Spread's about the same. They're not real tall skinny trees.

They're as wide as they are tall. Great small tree. If you've got a front yard that you don't have a lot of space in, the hawthorn's good. One thing to consider, the name hawthorn comes from the fact that they have thorns. If you want to put it as a front yard tree, that's fine. If you intend on your kids climbing the tree, it's not good. They've got thorns. There are different cultivars that have been grown to have less or less intense thorns. We'll talk about those. Just a great tree for that. One of the big issues with hawthorns, right off the bat when we talk about landscape uses, is they are susceptible to some diseases, specifically rust and fire blight.

Those are two different things. Rust is a fungal plant pathogen. There are thousands of rusts out there. One of the interesting things to me about rusts is that most of them require two hosts. The most popular, the most famous rust that I can think of is the cedar apple rust. If you have cedar trees with no apples nearby, you don't have to worry about it. If you have apple trees with no cedars nearby, and by nearby, I mean 1,000 feet to a mile. It can't be 5 feet away. They can't be anywhere near it. If you have apples with no cedars nearby, you don't have to worry about it.

If you get those two together, you've got a lot of problems because they share this fungal disease. This one's well known because the way it shows on the cedar tree are these orange balls with little tendrils coming out of it. It looks like something out of Cthulhu. It's this sci-fi weird monster thing. It's just bizarre. Again, the rust requires two hosts. The hawthorn is cedar also because it falls into the same family as apple. The cedar hawthorn rust. Other types of rusts, white pine gets a rust, and current is actually the host. Current's the fruit. Ryegrass, we get rust in our turf a lot. We treat fungicides in our turf. If you live in the north, you've got rye turf. Buckthorn is actually the other host.

You've got to have those. Rust is a problem with hawthorns. Fire blight, which is an infectious bacterial infection of the rose family. Fire blight's very difficult to control. Both these things can be controlled through products. Also, through some natural approaches. If you have fire blight in your trees, proper sanitation of tools while you're trimming, cutting out diseased portions of that tree with tools after each cut, sanitizing those tools, and then making sure that any branches that fall to the ground through wind or storms or whatever, get them off the property as quickly as possible. Bag them and send them away to get that bacterial stuff out of there, for lack of better words.

Doug: Do you see fire blight a lot on hawthorns or not that often?

Lou: Yes. Hawthorns, pear, and crabapple. All three of those are popular landscape use trees. I spend most of my time in landscapes, less time in the forestry world. I'm not an urban forester. Urban forestry is my realm. We see that a lot on those three species.

Doug: Can it be controlled? You've talked a little bit about it there where you're removing any excess branches that have fallen off and sanitation.

Lou: It can be controlled. The easiest way to control it, though, Doug, is to plant cultivars that are less susceptible. Through lab work, we have found ways to create tree species that have certain benefits, all sorts of different ones. We do a whole series on cultivars and what it means. These cultivars, particularly, are resistant to disease.

Doug: How about rust? How hard is rust to control?

Lou: It's not terrible. Copper-based fungicides during leaf out. When we do leaf disease, leaf disease is a catch-all term for fungal diseases that present themselves in the leaves of trees. What we do is, in the springtime, we pay attention to tree species that are susceptible to fungal infection, like rust. When those trees start to first bud out, when you see those buds just start popping, treat them with a fungicide.

Then about when they're halfway leafed out, treat them with a fungicide and then a third time when they're fully leafed out. That ideally keeps those fungal spores from popping on those trees. The timing's very important. At Davey, we use the Nature Clock, which is a cool algorithm based on weather inputs from weather stations across the United States that we use to time our applications on trees for all sorts of things. Specific to this conversation, we use it for fungal outbreaks.

Doug: What else do I need to know about this hawthorn besides that it has thorns on it? Maybe I'll plant it so the kids don't come into the yard.

Lou: Let's talk about the two that we see most, the two hawthorns that we talk about most in the landscape. The first one's the green hawthorn, Crataegus viridis. Crataegus viridis is native to the southeast United States. We have it here in Maryland. Native range is on the eastern shore of Maryland, actually up into Delaware. It's the southeast US. Habitat is lowland areas.

It loves valleys and swamps with medium to wet soil. The green hawthorn, the straight species, is great in full to partial shade. This is a really good one if you have a shady yard, and you want a tree to plant back there. Green hawthorn. Think about dogwoods, too. Dogwoods like that heavy shade, red buds like. I guess they're more edge species, but they can handle that.

Doug: How big on the green hawthorn?

Lou: 25 to 30 feet at the most. If you're planting in heavy shade, it's not going to get that big. If you think of ironwood, musclewood, same tree, that's another one that can handle shade. Good native one. When you're looking for that shade-tolerant tree, understory tree, this is one of them. That green hawthorn has yellow to green leaves. They've got a really nice scarlet-red fall color, too. Their flowers are prolific. They're white. Very showy flowers that bloom in March to May in the central United States. Their thorns are one inch to an inch and a half. They're smaller as far as hawthorns go.

Now, the Winter King cultivar is a very, very popular cultivar of that green hawthorn. That has thorns that are so small they're inconspicuous. I've pruned a lot of Winter King hawthorns, and I have not come away bloody as opposed to other hawthorns that are just awful to prune. The Winter King's a great one. The Winter King's also less susceptible to those diseases we talked about.

This is one of those cultivars. A cultivar is a subset of a species. This is a cultivar that has been bred for very specific reasons. Less susceptible to disease, smaller thorns. Makes it very friendly for the landscape. The mature species of that winter king also has an exfoliating bark. We've talked about on past episodes, a four-season tree for your landscape. A tree that has benefits all four seasons.

The winter king hawthorn has that beautiful exfoliating bark in the winter. If you think of crape myrtles or river birches, help me out, sycamores, trees that you look at the bark in the winter and go, "God, that's spectacular." Then you've got spring flowers that are a beautiful show. The summertime hawthorn, the leaves are showy as well, great size, great shape, and then you've got that scarlet fall color. The Green Hawthorn Winter King is a spectacular four-season tree.

Doug: Now, do you think I could get away with that in my Zone 6 kind of hilly forest? Would it be too dry for it?

Lou: I think the Winter King could work up there, yes. I would check the zonage on it, but I believe the Winter King could work there. I remember working on Winter King's back in Cincinnati, and you're pretty similar [crosstalk]

Doug: All right. Yes, we'd be okay. I would just concern more also about the dryness of my forest. It's pretty dry because we're mountainous here. It's acidic soil and hilly.

Lou: Now, the other hawthorn that we're going to talk about, the Washington Hawthorn, Crataegus, [chuckles] I'm going to try this one, phaenopyrum. Crataegus phaenopyrum is the Washington Hawthorn. That will grow in colder climates. Now, it prefers more sun, not full sun, full to medium sun. It is shade tolerant, but that one has some pretty severe thorns on it.

The leaves, they emerge reddish purple in the spring, and then they turn a very dark green in the summer. Beautiful. The fall color on this one is also spectacular, orange, scarlet, purple, just a good mix of them. Now, the Washington Hawthorn has those late spring blooming white flowers. Again, they're showy, and they also support pollinators, so an important tree for your pollinator friends. The berries on the Washington Hawthorn, same as the Green Hawthorn, they're small red berries. They're clustered, and they show up in late fall, and they persist into winter for the birds and the squirrels.

It's another reason why the Winter King is called the Winter King. It has those berries that tend to stay on later, like a holly tree. You get those red pops in your forest or landscape. On the Washington Hawthorn, they've got 1 to 3-inch spiky thorns, as opposed to that Green Hawthorn that has 1 to 1.5 inch. These are daggers. These will mess you up. I've had some bad run-ins hand-pruning Washington Hawthorns. I still love them. They're one of my favorite trees out there. Now, there are two thornless varieties that come to mind, so thornless cultivars, the Princeton Century and the Fastigiata.

If you're planning on pruning them, those are two good ones. They tolerate aggressive pruning, though. These are trees, because of their thorns and because of their tolerance for aggressive pruning, they've been used for, I want to say, thousands of years in Europe for hedges, because you can grow them, you can prune them into squares, and no one, either people or livestock, want to go through them.

You'll be bloody. They've been used as hedges for a millennium. These trees tolerate urban pollution and heavy clays, so they're great for street trees, minus the thorns. You get the thornless varieties, they're terrific. If you've got power lines over your sidewalk, and you need to find a tree species that can grow under those power lines in garbage soil, as most sidewalk cutouts are, Washington Hawthorns are terrific for that.

Doug: Have you seen these cultivars that don't have thorns?

Lou: I've seen them and worked with them, and they're terrific. They're true to form. They're thornless. You'll get a couple popping out here and there as the rootstock tries to overtake, but they are great species.

Doug: Sometimes when they breed something like that into a plant, you lose something else. In this case, these thornless ones, you like?

Lou: Yes, I do. I like using them. I think they're a great option for the homeowner and landscaper.

Doug: See, now that you explain what the tree is, I've seen it when I think of those red berries and the thorns. Do you see them in a lot of landscapes where you're at?

Lou: Not as much as I would like to. It's an underutilized tree. It's gaining more popularity. As we've realized over the past 20 to 30 years, those calorie pairs that were the go-to for the medium-sized flowering tree in the American landscape, we now know that that was a monstrous mistake for many reasons for a different podcast. This is a great replacement for that. This is a tree species that can take that place. We're starting to see more use. Yes, still, it's not a heavily used one. I'd like to see more of it.

Doug: Tell me a little bit about when you can educate a client and bring a tree like that into their life. That's the part of working with an arborist, one of the parts that I love is being educated and saying, "Oh, man, that would be a great tree. I'm thinking right now, from you, this would be a great tree to add to my forest." How is it for you when you're able to, not convince somebody, but make this choice available, something they never would have heard of before?

Lou: It's a great feeling. Connecting those dots, helping people-- People think of arborists as just, "Oh, they go out and cut trees." Yes, we do that, but we do a lot more than that. Like you're saying, providing consultative services to homeowners on what species work and which places on their property is really important. There are a lot of landscapers out there who have arboricultural certifications, or at least knowledge, and they can talk about that. There are a lot of landscapers who rely on arborists to provide input. Unfortunately, there are some landscapers that don't. They end up planting the wrong tree in the wrong place, but everyone has things.

Yes, when I can talk to homeowners about replacing trees or planting trees and finding a species that connects for their space and for their desires, that's the big thing, too. I could talk until I'm blue in the face about why this species is important. If you don't want it, there's no point in that. Trying to find out as a homeowner what your plan is, what your desires for your property are.

How long are you going to be at this property? How do you utilize your space? Do you look out this window? Is this the kitchen window that you're-- I spend a lot of time standing at my sink. I wash the dishes in the house, one of my favorite chores. I have a window that I stare at. I've got two white oaks with a bird feeder hanging on it. I've got a dogwood in the background. I can close my eyes anywhere, and I picture that view, and I love it. Is this a space that you spend a lot of time looking out the window?

All right, let's line up. What colors do you like? What textures do you like? What sizes do you like? Trying to help homeowners come to a place where they are not only comfortable, but are excited about the future because this is a long-term investment. It's financially an investment, obviously, but it's the long-term. When you plant a tree, you're in it for the haul. You can always cut it down if you want, but if you make that decision to correct the first time, you've got 30, 40, 50, some species, 600 years of enjoyment. Making that connection is really important for me.

Doug: Lou, I love that. I'm going to tell you a little story because looking out my window when I'm doing the dishes is a flowering crab apple that I inherited when I moved to this property. A pine tree behind it had come down on it. The guys from Davey came, and I said, "Please, I know it's going to look funny now, but please, can you prune it in a manner that can save it?"

They were so understanding of that. Not everybody would be understanding. I wanted this tree to survive. Yes, he showed me where the first cuts were going to be. He goes, "Right now, it's going to look weird, but you want to save it. We're probably 10 years down the road now, and you wouldn't even know that it was pruned." That understanding of our love of our trees and what you just explained is one of the reasons that you should be using a certified arborist to get your tree work done.

Lou: 100%, absolutely.

Doug: Lou, I can't wait for our next one or whatever our next species is. These have really been fun to talk about the tree species, and people have really reacted to them well. I just want to thank you again. It's always fun talking to you, buddy.

Lou: Doug, it's my pleasure. Talking trees with my good buddy Doug is one of my favorite things in the world.

Doug: All right. We'll talk to you soon. There he goes. I think you can tell how much Lou and I enjoy talking with each other. Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host, Doug Oster. I need you to do me a favor. Subscribe to the podcast so you'll never miss a show. If you've got an idea for an episode, maybe a comment, there's two ways to reach us.

Send us an email at 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 ideas might be in a future podcast, and we'd love to hear from you. As always, we like to remind you on the Talking Trees podcast, what else? Trees are the answer.

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