Frost Cracking, Sugar Maples and Syrup Making

R.J. Laverne, Manager of Education and Training for Davey Tree, talks about identifying maple trees, who can make syrup and what to do about frost cracking on your trees.

In this episode we cover:

• Benefits of Sugar Maples (0:45)
• Maple syrup making (2:53)
• Frost cracking (6:13)
  • Species prone to frost cracking (8:20)
  • Young trees and damage to circulatory system (9:45)
  • Port of entry for decay producing organisms (11:24)
  • Anything you can do? (12:26)
• Identifying maple trees (14:02)
  • Identifying Sugar Maples from Red Maples, Silver Maples and Norway Maples (15:55)
• Why R.J. enjoys his job (17:38)

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

To learn more about syrup making, read our blog, Tapping Doesn't Seriously Damage Maple Trees (But Don't Plug Holes).

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

Transcript

Doug Oster: Welcome to the Davey Tree Expert Company’s podcast Talking Trees. I'm your host Doug Oster. Each episode showcases one of Davey's certified arborists sharing advice with everyone about caring for your trees and landscapes. We'll talk about everything from introduced pests, seasonal tree care, deer damage, how to make your trees thrive, 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 guest today is RJ Laverne. He is the manager of Education and Training for the Davey Tree Expert Company. RJ, how are you today?

RJ Laverne: I'm doing quite well, thank you, and you?

Doug: I'm doing great. It's so funny when I talk to anybody in the tree business and I start to ask them about their favorite tree I'm expecting some kind of weird thing I've never heard about before but so often I hear sugar maples. Grow some sugar maples because they're a great shade tree and they're also beautiful in the fall. Of course, we think of a sugar maple as something that we can make maple syrup out of right?

RJ: Yes. I would certainly put that species in my top five as well.

Doug: What are some other things about that tree that makes it so good for you? Just the things I talked about or other things too?

RJ: Well, I guess it depends on what perspective you have. In addition to being a forester and arborist, I'm also a woodworker. From the forestry side, I love the tree because of its durability, and it's relatively resistant to insects, pests, and diseases. I love the environment where it grows. From the woodworking side, it's just a beautiful light creamy color wood to work with. It's very dense but works nicely with hand tools or power tools.

Doug: Well as a woodworker, I think you've picked the perfect job because you have access to all sorts of different types of wood from work, right?

RJ: That's one of the benefits. In addition to looking for wood that I can use in my woodshop, I'm always looking for wood that I can use in my woodstove. That's one of the benefits of working for Davey Tree. I have yet to have to pay for a single stick of firewood.

Doug: Another benefit for working for the Davey Tree Expert Company.

RJ: Just goes on and on and on.

Doug: [chuckles] All right, let's talk a little bit more about sugar maples. If I have sugar maples in my landscape, can I make maple syrup from them?

RJ: Well, the short answer is yes but the better answer is you'd better have a lot of sugar maples because otherwise, you're not likely to get as much syrup as you will need for a single pancake on a sunny Sunday morning.

Doug: [chuckles] How much of the sap does it take to make some maple syrup?

RJ: To get one gallon of maple syrup you'll need on average about 40 gallons of sap from the sugar maple tree.

Doug: I guess I'll just drive into Amish country and get the real thing then, huh?

RJ: You could do that, that would probably be the more efficient way to go at it.

Doug: I wonder are sugar maples the only type of maple that you can make maple syrup from?

RJ: Well, no, you can actually pull sap from other species of maples including red maple and silver maple. The sugar maple species has the highest concentration of sugar in the sap and will give the highest quality of maple syrup. Actually, any of the trees potentially could be tapped. You could make syrup from walnut trees, from hickory trees, from birch trees because all of these species of trees create sugar in the process of photosynthesis.

It is certainly the maples and in particular, the sugar maple that has the highest quality, highest concentration of sugars in the sap.

Doug: Anybody making maple syrup is going to use a sugar maple, right? No?

RJ: Well, you can certainly buy what is labeled as maple syrup. That will be primarily from other species, notably red maple and silver maple depending on where you go in the country and you buy your syrup. Sugar maples tend to like northern climates. When you're in places like Michigan and Vermont and in Maine, Minnesota, more than likely the maple syrup that you get from those regions will indeed come from sugar maple.

As you work your way farther south, sugar maples tend to become more sparse and the red maples and silver maples are a little bit more plentiful. As you work your way south, you're your pancake syrup may very well come from these other species.

Doug: Oh, that's interesting. In your opinion, sugar maples make the best maple syrup?

RJ: In my humble opinion, I would certainly agree.

Doug: Now let's talk a little bit about frost cracking on trees. Tell me what that is and how it happens.

RJ: Well, it usually takes place on tree species that have relatively thin bark, and those are primarily the younger trees. Some species are more susceptible to frost crack than others. Norway maple is one that comes to mind. What causes these cracks is in late winter and early spring. When the sap starts to flow as a sidebar, so what really kicks in the sap flow in maple trees and other trees is when the temperatures in late winter, early spring drop below freezing at night and they rise above freezing during the daytime.

When you get sunny days in the late winter, early spring, that's when the trees will really start with the sap flow. What causes the frost cracks is when the sap really starts to flow in late winter and early spring and you get these shifts between sub-freezing temperatures and above freezing temperatures, the sap will start flowing in the vessels in the tree when it's warm during the day and then if you get a rapid decrease in temperature, the liquid sap that is starting to flow in the vessels in the tree will quickly freeze. As the sap freezes, it expands and that's what causes the cracks in the bark and in the outer layers of the wood.

Doug: Are there any other species besides maples that are also prone to frost cracking?

RJ: Yes, and again, it's primarily those broadleaf species that have relatively thin bark as they’re young. Birch trees, to some extent the hickory trees, any of those trees when they're young that start pumping the sap early in the springtime and are subjected to those rapid declines in temperature can experience the frost cracks. We see that primarily on the maples especially red maples and Norway maples.

You'll probably notice also that the frost cracks will occur primarily on the south-facing sides of the tree because that's where the sunlight will hit that face of the tree. The southern part of the tree will tend to warm up more than will the northern side. Then if you get the sap flowing and you have a rapid decrease in temperature in the nighttime, that's when you'll have a tendency to get more of the cracking.

Doug: When a tree is young, is this a serious thing? Could this be a fatal thing for a tree depending on the severity?

RJ: For the most part, the cracking occurs through the bark and just underneath the bark. Frost cracks rarely go deeply into the wood, into the heartwood. Anytime that you have a break through the bark and into the wood of the tree, there is some damage to the circulatory system of the tree if you will, because all of the water that is coming from the roots is drawn up through the most recent growth rings of the tree right underneath the bark.

All of the sugars, all of the photosynthates that the tree makes in photosynthesis, flow down from the top of the tree on the inner layer of bark. All of that movement of water going up the tree, and sugars coming down from the tree, all of that happens in a thin zone right underneath the bark. When you have a crack that disrupts that, you have a momentary pause, if you will, in a small area of the circulatory system of the tree at that point. Also, over a longer-term, anytime you open up a wound through the bark and into the wood, that is a potential port of entry for decay-producing organisms.

Fungus spores can enter those cracks and decay can become established, and over the period of years, that decay can advance. In most cases, when we see frost cracks on trees, those cracks will seal over. They won't heal over in the same way that our skin heals over when we cut through it. The tree can't create new wood cells to replace those damaged wood cells, but they can create new wood cells that will seal over the crack. In most cases, those frost cracks will seal over with the following year's growth.

Doug: That leads me to my next question. Should I do anything when I see a tree with a frost crack?

RJ: No. The conventional wisdom used to be when there was a wound on the tree, for example, if we would prune a branch off of a tree, the conventional wisdom used to be that whether it was a pruning wound or a crack, we would try to seal it over almost like putting a bandaid on us when we get a cut in our skin. The problem with that is that there are always fungal spores that are floating in the air.

When you cover over a crack or over a pruning cut, for example, you're really making a nice warm dark incubator for those fungal spores that have already landed on the wound. The best thing that you can do for a tree that has a frost crack or has an open wound from, say, a pruning site is to leave the crack open, leave the pruning wound open to the sunlight and to the air because those conditions are not conducive to the germination of the fungal spores. Really leaving it open to the sunlight is about the best that you can do.

Doug: One thing I was thinking about when we were talking specifically about sugar maples is how can they be identified in the winter or is that something that is identified by the homeowner, by the person who's getting the sap during the spring when you see the leaves? Can you tell what a sugar maple looks like in the winter?

RJ: Yes. The first way to identify whether the tree is a maple versus say an oak or hickory or a walnut, for example. If you look closely at the small twigs on the branches, maple trees will have the twigs and indeed the branches coming out in pairs on opposite sides of the branch. When you look at the upper crown of the tree and you see that the twigs are coming out in these pairs that are opposite of one another, that is an indicator that you're looking at either a maple tree, an ash tree, or a dogwood tree.

Those are the three major types of trees that have this opposite branching. Most other trees like oaks and birches and hickories and walnuts will have twigs that come off of the branches in an alternate pattern. You'll have one twig that comes off on one side of the branch, and then there'll be a little space of a few inches and then you'll have another twig that comes off at the opposite side. Simply by looking at the arrangement of the twigs, you'll get an idea that you're looking at a maple tree.

Then within the species of maples, the way that you can easily identify a sugar maple from the other two major maples that we see, the red maples and the silver maples, or Norway maple for that matter, is the size and the shape of the buds. Sugar maples will have relatively small, dark brown pointy buds at the ends of the twigs. When you look at the twigs, you almost won't be able to tell that there is a bud at the end of the twig.

On the other hand, with the silver maples and the red maples, they'll look like they have little red babies that are attached to the end of the twigs. You'll be able to see these little round babies that are the buds from a fair distance. Then on the Norway maples, they also have buds that are quite a bit larger than sugar maple. If you look at the buds of a Norway maple, they're not perfectly spherical like you see on a red or a silver.

If you use your imagination and you look at the buds on a Norway maple, it looks like a beak of a puffin bird. Some people think it looks like the beak of a parrot, I think it looks more like a puffin. Just looking at the size and the shape of the buds will help you identify the various species of maples.

Doug: Tell me a little bit about why this job is right for you? How did you come into loving trees and learning so much about trees and now being able to teach arborists and others about trees?

RJ: Well, I have to make a confession first. It wasn't always my intent to be a forester or an arborist. When I was a young boy, my hero was the great oceanographer, Jacques Cousteau. I wanted more than anything to be a marine biologist. When I started in college, I enrolled in a biology program with the intent of going on to be a marine biologist. About three years into my studies, it occurred to me that I didn't know how to swim and that the job opportunities for a marine biologist that couldn't swim were probably pretty narrow.

It was at that point that I shifted gears and I decided that I wanted to go into forestry. I guess that was probably because when I grew up in Detroit, the house we lived in, on the back fence, you could jump over the back fence, and be in an undeveloped woodlot that was, I don't know, maybe 5 to 10 acres. I spent an awful lot of time roaming through this little woodlot when I was a boy. That's where I got my first introduction to how trees grow.

I went on to get my forestry degree. Then little by little after working in traditional forestry in northern Michigan and in Maine, I came to realize that I really was interested in trees in cities. I guess that's just because I grew up in a city. That's what drew me to the Davey Tree Expert Company. I have enjoyed a lengthy career of working with trees in communities.

Doug: I wanted to finish up and ask you a little bit about what you get out of that part of your job that educating and training people all over the country.

RJ: The interesting thing about it is that our company, the Davey Tree Expert Company, takes a lot of pride in our history and even in the name of the company. In reality, we have never gotten a phone call from a tree that has said, "I'm sick, can you come and look at me." We've never gotten a paycheck from a tree after we've provided the help. It's always been the homeowner or the municipal arborist that we get the phone call from that's saying, "Can you come and help us with our trees," or even the students that are learning forestry or arbor culture.

In addition to my work of Davey Tree, I also I'm on the faculty at Michigan Technological University where I teach the urban forestry course. It's a really good day when I get to spend time with hands-on trees and walking through the forest, but it's a really, really good day if I get to spend time with people who are interested in trees, perhaps people that are seeking help for their landscape trees and we get to share ideas about these incredible living organisms that provide us so many benefits from oxygen production to reducing air pollutants, to reducing stormwater runoff, to giving us sap for maple syrup, and wood for our fireplaces and our humble wood shops.

Doug: Well, RJ, we're going to leave it right there. Thanks for all the great information and the great stories.

RJ: It's been my pleasure. Anytime I can talk trees it's a good day.

Doug: Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host Doug Oster. Next week, we're talking all about the best wood for the fireplace and have important information about chainsaw safety. Remember on the Talking Trees podcast, we know the trees are the answer.

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