Every homeowner knows they should prune, but beyond that, there’s a lot of confusion. Making things worse, there are examples all around us of poor pruning: fall snipping, summer shearing, tree topping, the list of pruning transgressions goes on and on. In this episode of Granite State Gardening, UNH Extension’s Emma Erler and Nate Bernitz share proven tips and solutions for approaching the ever intimidating and often-counterintuitive task of pruning. Come for the accessible science, stay for the demystifying banter. Once you learn how to prune, you’ll never see the trees and shrubs all around you the same.
- Featured question: Can trees be topped to reduce their height?
- Featured plant segment: Vernal witch hazel (Hamamelis vernalis)
- Closing gardening tip: Staking trees
It’s Pruning Season article, with information about upcoming events: https://extension.unh.edu/pruningseason
March 17 live event with Emma and Nate on Pruning: https://extension.unh.edu/events/pruning-ornamental-trees-and-shrubs-online
Basics of Pruning Trees and Shrubs fact sheet: https://extension.unh.edu/resource/basics-pruning-trees-and-shrubs-fact-sheet
Pruning Deciduous Trees fact sheet: https://extension.unh.edu/resource/pruning-deciduous-trees-fact-sheet
Pruning Hydrangeas fact sheet: https://extension.unh.edu/resource/pruning-hydrangeas-fact-sheet
Science of Pruning webinar Q&A: https://extension.unh.edu/blog/science-pruning-qa
Cleaning and Sharpening Pruners: https://extension.unh.edu/blog/how-clean-and-sharpen-your-pruners
Nate Bernitz 00:00
Welcome to the Granite State gardening podcast from UNH Cooperative Extension. On today's show, we dive into the world of pruning. At the top of the show, I want to put in a plug for a series of online events we're offering on this very topic. The first is on March 9 on pruning fruit trees, then on March 11, on pruning blueberries on March 15, it's burning raspberries, blackberries and grapes. And finally on March 17, ornamental pruning. If this episode leaves you with questions, join us on March 17. To ask me those questions live. These four events will all be streamed for free on our Facebook page, ask UNH extension. And I'll play host and moderator speaking with extension specialists including Emma and Becky Seidman, who you know from our vegetable garden planning episodes. Check the show notes of this podcast for the details. And speaking of the show notes, we have links to several parenting resources Emma has written herself and one of the things I appreciate most about these resources are the hand drawn diagrams Emma has done which really help illustrate these concepts. Greetings Granite State gardeners. I'm Nate bernitz. co host with me earlier of the Granite State gardening podcast a production of UNH extension. Today we're talking about pruning and specifically pruning ornamental trees and shrubs. So not the trees and shrubs that grow edible fruits because we're going to devote a whole other episode to printing those up. Now today we're talking about pruning landscape favorites like hydrangea, lilacs, Rhododendron, and well you get the idea. You may refer to pruning as trimming or cutting, but for today, we'll use the word pruning. Our goal here is for you to feel confident about pruning, and understand just a bit about how plants actually grow and respond to cuts, you're going to find that is really helpful. Inevitably pruning is something that takes practice and experience as well as an understanding of how particular plants grow and what you'd like them to actually look like as the real expert here. So I hope you don't mind if I learn a bit right along with you. Okay, let's get into it.
Emma E 02:29
Can trees be topped to reduce their height. That's this episode's featured question. Topping a tree is the cutting back of large branches and mature trees, cutting them to Stubbs trees are often top because they're perceived as being too tall to be safe. This fear is largely unjustified though, as a healthy tree we'll have a root system that is adequate to support it. Topping has the potential to harm trees and actually make them more prone to breakage. Trees respond to topping by producing a lot of long sprouts below the cut of the large branch that quickly grow to the height the tree was initially. Additionally, these limbs are weakly attached to the parent branch and are very prone to wind, snow and ice damage, which can obviously be hazardous. Another thing to consider is that large pruning wounds from large branch removal often did not seal properly and invite decay and insect invasions into the tree topping can lead to a long slow decline of a tree. So topping trees is hardly ever a good option. If the height of a tree really needs to be reduced for some reason. My advice, work with a certified arborist to have the work done properly. Your trees will thank you.
Nate Bernitz 03:53
Emma I mentioned in the introduction how this is a kind of a separate episode from pruning fruit trees and shrubs. Can you just really briefly explain why this is kind of a different animal?
Emma E 04:07
Well, it's different I think for a few different reasons. First off, when you're pruning or ornamental trees, typically you're most concerned about having the best possible structure to promote the beauty of that plant, as well as the the health of that plant in general. Whereas if you're growing a fruit tree, you're more concerned about production than how that plant looks in the end, right. You just want to be able to get the most fruit you possibly can on a healthy tree. Are those two things different? Well, I mean, they are to a certain extent and it it gets more particular depending on the exact species that you're talking about. But the big thing is that you're you're either looking at promoting the beauty of the plant or you're trying to make it as productive as possible.
Nate Bernitz 04:57
Hence the word ornamental. So That makes sense. Let's start with the really basic question of wiper and what are some of the benefits and reasons why someone might want to look out their backyard window at the trees and shrubs out there. And think, yeah, pruning is worth my time, I should definitely be doing that.
Emma E 05:18
I guess I'll start by saying that pruning isn't something that you necessarily have to do in your landscape, it can be really important. But just because you have a tree or shrub growing in your garden doesn't mean that it needs pruning. But there are some key purposes to pruning. The first thing I think of is to maintain or create good structure within a plant. When when plants are young, in particular, their branches may not be in a in a form that's going to be healthy or conducive to that growth to the growth of the tree. As it gets older, it may develop some serious structural defects, meaning the branches are attached weakly by the angles that they are connecting with the main trunk. Branches may be very, very congested crossing rubbing each other. So maintaining that that really good, healthy, strong structure is the first thing.
Nate Bernitz 06:14
Forgive me, Emma. But why does that actually matter?
Emma E 06:19
I mean, first off, it can make the tree look better. Second of all, can make trees more resilient to things like storms. So especially in New Hampshire, where we get a lot of winter storms, ice, these things can put a lot of strain. So wind, like I said snow or ice can put a lot of strain on branches, and make them more likely to break. If they aren't attached to that tree in a really strong way, then we can talk about that a little bit more. But it really comes down to that the angle branches are attached.
Nate Bernitz 06:53
Are there other reasons why you might prune? I guess for me, I'm thinking really practically, like sometimes you want to prune because a plant is too large and growing where you don't want it to. So maybe it's growing against your house or growing into a power line or something like that. So there's a real practical element I think of as well.
Emma E 07:17
Controlling plant size is often one of the major reasons people prune. Now, if a plant was put in the best possible location for it to mature, then you probably aren't going to need to do a whole lot of pruning to control size. But be that as it may, you know that is a key reason pruning is necessary. Pruning is also important for keeping plants healthy in terms of disease issues in particular. So trees are much less likely to have issues with disease if there's good airflow through the canopy. Things are let's see, let's take apple or crab Apple, for example. A really common disease on these plants is Apple scab. This is a fungal disease, that tends to be worse on trees that have a very dense canopy. So a whole lot of branches really close together a lot of leaf matter that increases haven't having that density increases humidity. And the leaves will stay wetter for longer, which promotes fungal spore germination and infection. So opening up that canopy so that air can get through really will reduce disease incidents. So that's important too. And of course, pruning is also going to influence flowering and fruiting of a plant. So the way that you actually prune or train, the angle of a branch will impact how much fruit it bears will also impact how it flowers. So there's quite a bit that goes into it.
Nate Bernitz 08:52
Okay, so your birthday, I think just happened. But let's say that your birthday wish list was all the pruning tools you could possibly dream of, like just completing your personal arsenal. What would be on that list?
Emma E 09:09
Oh, gosh, well, there's so many right. But I think if you need just the basic pruning set, you know what, what's gonna get you by to do basically everything you need to, I'd say a good pair of hand pruners. So you want a nice quality pair that has you know, good steel blades that that are sharp walking mechanisms that on that pair so you can also carry them around in your pocket or in a holster fairly easily. There's a lot of brands out there and I won't get into that everybody has their their preference I have my own. But what I do like to look for is tools, or a ham printer that has some sort of warranty and that that the manufacturer provides spare parts for so it's possible To actually repair that tool as it goes along, not the least of which new blades because you will need them eventually. Beyond that having a nice pair of loppers is important, so long handled lopper that it that comes really in handy for pruning shrubs back in particular, you'll also want a pruning saw. And there's a lot of variation out there too. If you can only have one saw, I prefer a folding saw that it has at least a six inch blade. because that'll get you through, you know the majority of smaller cuts you need to make. And then if you have a whole lot more money to spend a pole pruner is helpful. So this is actually a set of pruners that is at the end of a long pole so that you can extend your reach that happened to be up on a ladder, a pole saw is really helpful. And then if you're really taking down bigger limbs or trees, a chainsaw, of course is helpful. But that that requires a little training to be able to use that safely versus other hand tools.
Nate Bernitz 11:07
So what the lopper that's just what a really big pair of scissors.
Emma E 11:12
I'm not quite so the blade part will look like a pair of scissors essentially where you have a blade, bypassing another blade, but the handles on this are really long and straight. So typically, I'd say at least two feet long, sometimes longer. This is going to give you leverage to make a little bit longer, or a little bit wider cuts I should say. So we're looking at branch diameter of let's say in an inch to inch and a half.
Nate Bernitz 11:41
You use the word bypass and I've seen printers that are labeled as bypass printers, but I've seen some that aren't. Can you explain the kind of different mechanisms these printers might use to actually physically make cuts and whether you have a preference?
Emma E 12:03
Yeah, for hand pruners. They come typically in two styles either bypass or anvil. So bypass pruner has an action just like scissors where you're having we have two blades essentially coming together, although in most cases is just one cutting blade. And an anvil style pruner you have a blade that connects with a plate. So instead of those blades going across each other, you have just a single blade connecting with a hard surface so it's more of a pinching action as opposed to a cutting action. Usually, I recommend bypass pruners because they do make cleaner cuts. But Anvil style pruners do have their place. So for pruning evergreens, where you're making a lot of really quick, smaller cuts on branches, Anvil pruners can be nicer just because they are a bit more efficient in the way they cut. And you can really speed up your your pruning time. But if you can only have one pair, then you'll definitely want to have some bypass pruners.
Nate Bernitz 13:05
Realistically, if you could only have one pruning tool, what would it be?
Emma E 13:10
If I could only have one, I think I'd choose my pruning saw. A lot of times I will use that my pruning sock exclusively and less branches are getting down to less than half an inch in diameter or so.
Nate Bernitz 13:25
That's, that's interesting. So you'd go with a pruning saw over hand printers.
Emma E 13:29
I would, yeah, I would. So they hit him pruners are really, really helpful for very small diameter cuts. So we're saying like half an inch or less, it's probably the most efficient tool for making really nice clean cuts. But for anything bigger than that, then you're looking at maybe loppers, but loppers are only good to a certain extent to probably from half an inch diameter branch to maybe an inch and a half. And anything after that you're using a saw. And of course, the sock can be used for smaller diameter cuts as well. So I think it's probably your most useful tool. And certainly, if you're doing a whole lot of pruning and you want to be really efficient, you're probably going to want that saw rather than switching between a whole bunch of different tools.
Nate Bernitz 14:18
And supposing that maybe you're not getting all these tools for one birthday or something. Because you really want high quality tools. So maybe as a gardener, you might consider investing in one of these tools a year or something to kind of build up your collection. And I say investing because you do kind of get what you pay for right? Yeah, like you're buying something more quality. It's built to last but then you have to maintain it. Right. So What tips do you have around maintaining these high quality tools so that you really do get what you invested in What's important about that, I think one obvious piece is keeping them sharp. I'm not quite sure how you do that with a saw, but I know you can definitely keep blade sharp.
Emma E 15:15
With the hand pruners and loppers, you are going to want to keep those blades sharp. And I'll just note too that if you're going to look to buy a quality pair of hand pruners, you're probably going to need to spend at least $30. The best pairs are going to be more like 50 or $60. For loppers, you're again probably looking at minimum 30 or $40. If you want the best then you're looking at closer to 75 or $100. With those tools, it's it's not that hard to maintain them if you keep up with it as the season goes along. The blades on loppers and hand pruners tend to be made out of steel, which will rust if they're left wet or stored wet, which is easy to do when when you've been pruning that sap that that ends on the blades ends up there can cause rusting any other sort of moisture, if you're out on a wet day can cause the blades to rust. So wiping them down after every use was really helpful at least to store them dry. If rust does start to build up, then scrubbing that away I find it useful to use steel wool to scrub rust away and then treat blades with wd 40. To try to prevent remove rust and prevent it from coming back. In terms of sharpening there are you know a bunch of different tools out there that you can buy. But basically what you're going to need is whetstone of some sort. And it's really important to sharpen that blade from back to front at about the same or ideally the same bevel that that cutting edge on that blade is currently at. So basically if you look at the edge of your pruners look at that taper from the flat part of the blade down to the sharp edge and you want to try to maintain that same angle. If you're using your pruners your loppers a lot, you may have to do this a couple times throughout the season or you know periodically every few weeks every month, you might want to be removing rust, oiling, moving parts so that they keep moving, you know smoothly and sharpening. If you don't do a whole lot of pruning, then once a year is probably fine. With pruning saws, most modern saws are really it's really not possible to sharpen them yourself. So in most cases, you can buy a replacement blade. If you've bought a really nice pruning saw from a company that's known for its manufacturing pruning equipment, then you'll be able to buy a replacement blade I found with with my pruning saws, you know this is with with consistent use, they still the blades lasts a few years. So this isn't something you're going to need to constantly replace unless you're doing pruning all day every single day.
Nate Bernitz 18:18
Gotcha. And I will note that at least the sharpening is a little bit of a challenging concept to convey, just throw it kind of out loud description, but you made a I think a really helpful video at least for sharpening hand printers and we'll have the link to that in the show notes. So check that out. If you're looking for a visualization. We haven't done that for loppers. But maybe we will.
Emma E 18:47
It's pretty similar. If If you figure out how to sharpen your print your hand pruners, you should be able to sharpen your loppers, by following this the same principles.
Nate Bernitz 18:59
Okay, then not necessary. So getting into the actual technique of how you use these high quality burning tools that are immaculately maintained and very sharp, because you're keeping them that way. What are the types of cuts that you're going to be making? Right? So we're understanding that not all cuts are equal. You're looking at different types of plants with different objectives in mind, maybe you want to control its shape. Maybe you want it to be nice and dense and full really depends on what you're trying to do. But what are the cuts that you're going to be able to use to achieve some of these different goals?
Emma E 19:46
What one thing that's really important to understand about plants is that their growth is is directed by plant hormones, as well as environmental factors as well within any tree or shrub, there is one really important plant hormone that's at play. That's called oxygen. And this is produced in green shoot tips and flows downward, which and stimulates shoot growth. So what we see in basically any tree or shrub is a phenomenon that we call atypical dominance, where basically, the atypical buds, so the bud that's at the very end of a branch, and if you look at a branch, it'll be the biggest one is producing oxygen, this plant hormone that suppresses growth of all other buds below it, this is what makes a tree, you know, grow up with a single central leader, if if it has the nicest form, because basically that that bud that's at the peak of a branch is suppressing growth of all the others. So knowing this, that's this is where knowing how pruning cuts are gonna affect a plant comes in. So if we know that the the end bud on a branch is producing this plant hormone oxygen, that's suppressing all the other buds, how we actually go about removing a branch is going to impact how the plant responds. So there are really two different types of pruning cuts that you can make on on any woody plant. One of those is called a thinning cut. The other is called a heading cut. With a thinning cut, what you're basically doing is cutting a branch back to an existing stem or branch. So if you're picturing, let's say, a branch that has one strong stem with an another slightly smaller branch coming off of it, you would be cutting the one branch back to the back to that junction where the other branch comes from that again, this might sound kind of kind of confusing, and we do have some diagrams, and a couple of pruning fact sheets that might be helpful for you to look at. But when you do this, when you cut a branch back to another existing branch or stem cutting, cutting just above it or cutting all the way back to the trunk, basically what you're doing is allowing the remaining branch to assume that atypical dominance or atypical control and so the end bud on that branch is then going to control growth from then on out. This is really essential for controlling growth on young trees. thinning cuts are what you're going to use most of the time, because they're going to help shape the plant without altering its overall size or growth habit. Heading cuts are the other type of cut. And basically what these mean is that you're cutting between nodes. So on a branch, this would mean you were cutting somewhere along the stem between two branches where they come off, or cutting to a very small branch or bud. And basically the reaction here is that many buds break and many new shoots form. So if you've ever seen a branch that just gets just cut off arbitrarily at a point and a whole bunch of new shoots originate just behind that cut, you're looking at a heading cut, and that is the typical response.
Nate Bernitz 23:29
Why would you make a heading cut? Can you give a couple practical examples.
Emma E 23:36
Heading cuts are used primarily when you're shearing plants if you're looking to create a lot of really dense growth. So a thinning cut is something you'd use. Really anytime you're pruning a tree or you know majority of shrubs that you're trying to maintain their natural habit. A heading cut is what you're going to use. If you are let's say shearing, a you hedge into let's say a particular shape, or you're you're trimming back and Arbor wajdi and you you're looking for a whole bunch of dense growth the form more of a hedge. shearing is is obviously a very particular application. And really, that's the only time that you're going to be using heading primarily in the landscape. Although I should know that if you are cutting something totally back to the ground in a process that we call coppicing or you're cutting it back to the same point every year, that is also a heading cut. So you're cutting these branches back with the expectation that a whole bunch of new growth is going to arise just below where you made that cut.
Nate Bernitz 24:48
so most of the time, we're doing thinning cuts. And yeah, you you brought up that kind of instance where you might be cutting a plant essentially to the ground. stimulate a lot of growth. I think that is a technique that you might use in some instances and not others. It seems really risky. If you don't know much about a plant, you don't really know what you're doing. You cut it to the ground, maybe it's gonna grow back. Or maybe you just killed that plant. So can you talk a little bit more about that technique and when you might use it, and when you wouldn't?
Emma E 25:31
Yeah, what you said there is important for backing up knowing what the plant or how the plant that you have is supposed to grow. How it naturally grows is so important, critically important if you want your plant to not only perform well, but also look really nice. So doing a little bit of research before you go out and start pruning is really key. In certain cases, you can actually rejuvenate a plant by pretty much entirely cutting it to the ground. And this works for really a subset of shrubs, it's not something that you would typically do with a tree. If the trees coming all the way to the ground, something has seriously gone wrong. But with a lot of shrubs, pruning them to the ground is actually the best way to maintain them. And to keep them looking really nice. great examples of shrubs you can do this with would include forsythia, so the nice yellow flowering bush that we all enjoy in the summer, spy Ria dogwoods. So really any of the shrubby dogwoods will prefer this type of pruning, and willows above, among many others. So again, knowing exactly what the plant you have is, is going to be key to deciding whether that's an appropriate way to prune or not.
Nate Bernitz 26:53
sometimes, you mentioned storms earlier, you might just have broken branches that need to be removed, is that a type of thinning cut, or is that kind of its own category of cut, where you're cutting basically, right to the trunk. And the whole goal there is just to remove the branch and get a nice kind of stump there, without necessarily stimulating a huge response, you just want it to heal.
Emma E 27:21
Yeah, so that is a thinning cut. So if you have a branch that's badly broken, you're gonna want to cut it back to the next large healthy branch or all the way back to the trunk. So those are those would both scenarios would be considered thinning cuts. And in many cases, that's that's exactly what you need to do. If you do have a broken limb, I should know that. timing of pruning can be important. But if you have any branch that's broken, diseased, actually, usually I say, dead diseased or damaged. If a branch fits into any any of those three buckets, then it's fine to remove that plant at any time of the year, or sorry, remove that branch at any time of the year.
Nate Bernitz 28:05
Why is timing important, though?
Emma E 28:08
That's a good question. So there's a few different things to think about when we consider timing with pruning. First off, for in some cases, plants have specific disease issues or pest issues that might be exacerbated if you prune the plant at the wrong time. A really good example is fireblight, which is a disease of plants that are in the Rose family. So Apple, crab, Apple pear, among others. fireblight infects plants through open wounds. So if you're creating a wound, while that disease is active, you are you are, you know, potentially spreading that disease throughout the plant through your pruning. Whereas if you make if you do your pruning while the plant is dormant, then this is no longer a concern that disease isn't active, you're not going to be spreading it around. The ideal time, in general, to prune the majority of trees and shrubs is in the late dormant seasons. So basically, this means late winter, or early spring. This of course, there are some caveats here. You know, depending on the exact plant you're growing, but in general, if you are pruning during this timeframe, so let's say from March through April, maybe even into May, the plants are just coming out of dormancy or just getting ready to come out of dormancy and enter a period of rapid growth. So if you make a cut in March, and that plant starts growing again, let's say by April, that wound isn't going to be open for very long before the plant starts trying to seal it over. Whereas if you make a cut in sometime in the summer, you might get a little bit of growth. To seal over that wound, but maybe not a lot in the fall, you're probably not going to get much at all. And any growth that does start is likely going to get killed by winter temperatures that that new growth won't have hardened off in time. So you're more likely to get die back at the site of pruning wound. If you are doing your pruning in the fall or early in the winter.
Nate Bernitz 30:23
I'm not trying to call anybody out. But honestly, the time of year I see most people pruning trees and shrubs is the fall, is that something you've noticed, too? And why is that?
Emma E 30:33
it is and I think there's a pretty simple explanation for it. It's much easier to prune trees and shrubs when their leaves have dropped off of them. And so when the leaves come off in the fall, you can easily see that branch structure and it, it seems like a good time to go ahead and get more yard work done, because you might already be outside raking leaves, putting putting the garden to bed. But if you can hold off and do that in the spring, your plants are going to be much better served. And you still have the benefit of being able to see that branch structure without any leaves obstructing anything.
Nate Bernitz 31:09
early spring can be a kind of challenging time, logistically because there may be snow on the ground. And if there isn't, the ground is probably sopping wet. Maybe it's raining, as it often does at that time of year. So it's not the most intuitive time to be out there spending a lot of time in the yard, but you're saying it's definitely worth it.
Emma E 31:28
It is. And if you only have a couple of plants that need to be pruned, you can wait until the ground is totally thought and dried, just before the leaves start to break on that plant, where people really need to get started early as if they have, let's say a commercial orchard and they have hundreds if not 1000s of plants that need to be pruned. So they're going to be out there in all conditions. But for just the backyard. I see no problem with waiting until the end of April to do your pruning.
Nate Bernitz 31:59
And that's for New Hampshire.
Emma E 32:01
That's for New Hampshire. Yeah, pruning time is going to vary a bit depending on where you live. But if you're in the northeast, you'll probably be able to do most of your pruning sometime in you know, late February, March or April.
Nate Bernitz 32:15
I guess my other theory about why sometimes or often people are pruning in the fall, in addition to what you said, is I think a lot of people think of pruning as just a way of controlling a plant. So it's spent all growing season growing. And at the end of the season, you're like, Oh, I don't want it growing there. And there. It's too big. It's unwieldy. So I'm going to cut it back. And I think your message is that burning is really not about directly controlling a plant, it's there's a little bit more to it than that you have to understand how a plant is going to actually respond to cuts, rather than just trying to cut it to the exact shape that you want it to be.
Emma E 32:59
That's exactly right. Yeah, I couldn't have said it better. And trying to control the size of a plant is really difficult to do through pruning, when a plant is has branches that are hitting the house that are coming up near a power line, it becomes really hard to control the size of that plant and have it still look really good. So it's important to if you are going to plant something, let's say a brand new tree or shrub, that you've done your homework and you know that that plant is going to fit the size that you have our size space that you have for it so that you aren't constantly fighting it with pruning.
Nate Bernitz 33:39
So when you are making cuts, should you be doing that at a particular angle?
Emma E 33:44
Yeah, that is true. So again, this is a little hard to describe. So looking again at our pruning factsheets is going to be really helpful. But when you are looking at a tree, let's say when you're looking at the way a branch connects to the trunk, there are a couple of features that you should be able to see that are going to tell you exactly where you need to make your cut. And these features are called the branch color and the branch bark ridge. Now, what are these look like? Ideally, you know if the if it's going to be a plant that that has these pretty clearly that branch color is going to look like kind of like an area of raised tissue that's on the upper side of the branch where it connects to the trunk. The branch collar or sorry, that's the branch bark ridge. The branch collar is a swollen area of tissue that you'll see often beneath that branch where it connects. And so there's these two things this branch color and this branch bark ridge. If you see one or both of those you'll have a better idea of how to make your cut. This, this is how it goes. So basically, if you see that branch collar, that swollen area of tissue, you want to make your cut at basically the same angle of that swollen tissue so that you're not cutting into it, you're cutting just outside of it. And if you just see that branch bark Ridge, so that raised bit of bark that's on the upper side of where the branch connects, then you'll want to make that cut at about the same angle, that that branch bark Ridge connects with the trunk. Now again, yeah, really hard to try to picture. But this is important. Because within that branch collar area, is a ring of cells that's called rather, it's it's called wound wood. And so this tissue that's inside that branch collar, is actually what's going to help seal over a wound. So if you disrupt that, you're gonna be basically eliminating the trees ability or shrubs ability to seal over that wound.
Nate Bernitz 36:03
So what happens if you cut at a different angle, so when I think of angles, I kind of think of you can either cut sort of flush, you can cut in or you can cut out, this may not be true, this is just how I'm thinking about it. So correct me where I'm getting it wrong. But I would think that the angle you would cut out would maybe dictate how the plant would respond, if it would send out, you know, new branches in a certain direction potentially. Help Help me understand and and by the way, I would know you're a great Illustrator. And one of the fact sheets that that you mentioned that this kind of basics of pruning trees and shrubs. factsheet in the show notes, has some illustrations that you did that are really helpful, I should take another look at the myself.
Emma E 36:52
Yes, do take a look at those. So the important thing and all this that in the angle of a cut is really just trying to preserve that tissue that's inside of that branch collar that is going to be responsible for sealing over a wound. Years and years ago, decades ago, the recommendation was always to make a flush cut, which basically means cutting the branch off as close as you possibly can to the attaching trunk. The problem there is that if you remove that ring of cells that that wound would that that wound is less likely to seal over. So basically what trees do, they they're not capable of healing an injured tissue like we are, they're basically capable of just sealing it over. So that's what they'll do with a wound. If you ever look at, you know, go outside and look at a tree in the woods, or one that's been pruned in your landscape and look for those cuts where they are made. If it was a good cut, then you'll see this basically ring of new growth that formed over that cut until there might be just the slightest dimple in the center, it's fairly easy to see. But if you cut flush, or if you cut into that branch color and wound wood of the tree, you might only be seeing new growth from one side of that wound. And the other part is just a you know a gaping wound that never seals over or it takes years and years for that wound to seal over for growth from just one side or maybe two sides to totally covered over. But this is this is important. And the smaller you can cut a branch or the smaller the branches that you cut, the more likely it is for that that tree or shrub to be able to totally seal over that wound. If you're making a very large cut, let's say on a mature tree that that wasn't pruned when it was younger, then a lot of times those wounds don't seal over entirely, or it takes so long that a lot of decay occurs in that wound before the plant can totally seal it over. So this is why it's so critical to prune trees, especially when when they're very small and very young and not waiting until they get very large and become an issue.
Nate Bernitz 39:13
Okay, well, thanks for setting me straight. That actually does make sense. I'm wondering though, if you maybe just don't make the cut kind of in a textbook way. Someone may not totally be following your advice, and then they're wondering, okay, how do I make sure that this tree or shrub heals properly? Can you just use some sort of product? I see a lot of these products that are there to help trees and shrubs, heal wounds, or maybe some sort of paint or sealant something that you're applying to that wound to cover it up is is that kind of an acceptable alternative? Or how do you look at those products?
Emma E 40:00
Yeah, it's kind of incredible to me that these products are still on the market. Because we've we've known for a number of decades now that these really aren't in the best interest of plants. And they can actually impede wound sealing over and encourage the growth of rot organisms and insect infestation. Because what these are going to do, so if we're talking about some sort of tar, or pruning sealer, or wound paint, what that's going to do is actually seal in moisture and potentially decay, creating the perfect environment for the K to occur for fungal organisms to break down that tissue. Instead, if you leave that wound open to the air, it's gonna end up sealing over much better. And, you know, this kind of makes sense when you figure that trees have developed effective mechanisms for this on their own. You know, trees in the forest don't have humans intervening trying to help them seal over their wounds. Because like I said before, unlike people or animals, woody plants aren't going to heal their damaged tissues. And though a bandage might be really helpful for us, that's really not helpful for a tree at all. So I would skip those products. And by the same token, if you have a hole in a tree, where an old wound did did allow some decay, to get in, maybe the interior of a tree is starting to break down. You also don't need to fill that in with anything, so no need to fill trees with cement. It's not helping the tree on a tree or a shrub, the only part of it that's actually living when you're looking at a branch or a stem is just a very thin layer of cells. It's called the cambium. So that vascular tissue that's right beneath the bark, the interior where all the wood is on the inside. That's not living cells. So plants can survive, even if their trunks are totally hollow, or trees can survive, I should say.
Nate Bernitz 42:09
That's amazing. And it makes me wonder what other kinds of products are out there that claim to do one thing and in effects kind of undermine that very purpose. But I guess that's for another episode. Spring is a time when a lot of people are bringing home young trees and shrubs. It's really just not financially feasible, in most cases to buy mature trees and shrubs just really expensive, because it took many years of growing them to get to that size. So we're often bringing home fairly young plants. And you mentioned earlier, how important training is for kind of getting these trees and shrubs off on the right foot. Can you I guess expand on that talk more about the principles of training? Is there more to it than certain types of pruning cuts are we also talking about staking and other techniques here?
Emma E 43:24
there's a little bit more to it. Usually when you are planting a brand new tree or shrub, you shouldn't have to do too much pruning right away. The only thing that I only things that I would be removing potentially would be broken branches, or any branches that are crossing right on top of one another or rubbing against one another. But if you if you're getting quality plants from the nursery, these features probably aren't going to be noticeable are really there. To begin with. What you are going to be looking for, let's say in trees is a nice even branch distribution around the trunk. So ideally, you should have branches that are coming off on all sides. So if you were to look at that plant from above, the branches coming off would look like spokes on a wheel versus all the branches coming off of one side of the plant. If if that is happening, if all the branches are pretty much clustered on one side, then you may want to remove some of those branches, which should in turn, stimulate or release some bud growth on the other side of the plant. It's also important to note to on young trees, that a lot of the branches near the base aren't going to be permanent. So don't get too stressed out about branches that are only two or three feet off the ground. If they aren't perfect or if they're too low. These are going to be removed eventually over the course of that plant's life. So leaving some of those on initially is totally Fine. One other thing you're gonna want to look for on trees is the actual angle that the branches are attached to the main trunk. What you're looking for a really eye, ideally, you're looking at a 60 degree angle or so would be absolutely perfect. So you know, pull out your protractor and see what that looks like. But that that's kind of the ideal attachment angle for the majority of trees. And the reason for that is that when branches are held at that angle, they tend to be pretty productive. So if it's a plant, or a tree, that flowers you should see plenty of flowers, maybe some fruit development there. And branches that angle are also structurally sound. If the branch angle is really, really narrow, let's let's say it's 20%. If any stress is put on that limb, it's more likely to break away from the main trunk. So this is where snow and ice really come into the picture and why trees that naturally tend to have very narrow crotch angles tend to break more. classic example is calorie pear or Bradford pear. These are ornamental pear trees that are planted really commonly on in around homes along streets. But these are really prone to splitting from ice or snow damage. Because those those angles are so narrow, they're very, very likely to break away.
Nate Bernitz 46:35
So it sounds like at least in year one, you're not doing a heck of a lot. And really the training starts kind of the following year. I bet for a lot of gardeners, it's that following year, when you kind of stopped thinking about that plan, you think a lot about it when you first plant it, and right when you're supposed to really be doing this work of training it to get to the adult form that you want and to be a healthy plant for the long term. That's when it's kind of out of mind. To what extent does the way you train and prune trees and shrubs depend on what it is? At least for me, I'm thinking about some kind of broader categories, I think about our evergreens, plants that that keep their, their needles leaves all year, I think of kind of flowering trees as maybe their own category, although there may be categories within that. I think about hydrangeas as kind of being their own category there. There are lots of different groupings, I would think. So how do you go about, at least understanding this at a basic level, of course, we're not going to go into detail on the exact specifications for how to burn all of these different plants today. But hopefully, you can explain the basics of how to categorize them and basic considerations as well as how to actually learn more.
Emma E 48:04
When I think about pruning different types of plants, I'm not so much thinking I need to change my technique as I do my approach with evergreen needle trees. Those are plants that I really don't do much pruning on at all in the landscape. And honestly, if if an evergreen tree has been planted in the right location in a landscape, it really shouldn't need much. plants like pines, spruces, hemlocks, have very strong apical dominance. So they'll naturally have that nice conical shape and should have just at one central leader, so you really shouldn't need to do any formative pruning early on in that plant's life, the only thing you might need to do, if there's some sort of damage to that plant, then you might need to get in and do a bit of training. But otherwise, I just kind of want to gloss over those for now. So your evergreen trees leave those alone, they really aren't going to need much in the way of pruning. It gets a little different though, if we're talking about needled evergreen shrubs. These sometimes do require a little bit of shaping to get them to fit a location to give you the design aesthetic you're looking for. So I'm thinking of right now junipers use maybe Arbor wajdi, camera Cypress. The deal with these plants is that some of them will produce new growth from the brown areas in the STEM, the areas where there aren't any living branches coming off, some of them won't. So you need to know specifically what type of plant you have. And then how it's going to respond to those pruning cuts. So for example, if I have, let's say, a you, I could prune that shrub really, really hard, meaning I could cut a branch back basically to a stub where it Have a brown stick leftover. And typically I will get some new growth coming out below that cut. But if I do that same thing to a Juniper, it's unlikely that there's going to be any new growth. So if I'm trying to prune that plant a little bit, I do not want to prune any further back, then I don't want to prune past the point basically, where there are some some green living needle branches. Additionally, with these shrubs, you typically don't want to remove all of the new growth, you can shorten it. If you're doing some shearing, which again, I don't really recommend, you could remove an entire branch if you need to. With a thinning cut, that's going to be acceptable as well. But you don't want to entirely denude it removing all of the new growth all at once. You have to account for, you know, evergreen shrubs, so needle evergreen shrubs getting bigger over time as well. They're, they're gonna continue to grow. And you do need to allow some of that growth to be there. And in terms of timing for those plants. I'm thinking early summer, you know, right after the growth flush. Again, pines are a little different. With pines, you're actually pruning back candles so that that new growth that comes out, before the needles expand, you can you can shorten that growth. But that has to be done in a very specific time in the growing season. And if you prune too late, you could really end up damaging your plant. So research, research, research or reach out to you and H extension, if you have a question about pruning a specific evergreen. So, the other group of plants, of course we're talking about are deciduous plants with deciduous trees. There really aren't any particular things that I'm thinking of, I'm just paying attention to the timing of pruning. So even if it's a flowering tree, I am going to prune in the late dormant season. So I am going to prune in February, March maybe into early April. With deciduous shrubs, then I'm thinking of a couple of different things, right. So I'm thinking of blooming time on these plants. And I'm also thinking about what sort of pruning they will tolerate. So there are a couple different approaches with shrubs. In terms of pruning, there are some that will create, let's say, three, four or five main stems. And you're pretty much just going to leave those stems alone, you're just going to work on shaping that plant selecting branches here and there, maybe removing some that are crossing and rubbing but the main architecture of that shrub you're going to leave alone. I'm thinking let's say of a Korean spice viburnum, I am going to leave that the main trunks alone, those are integral to the structure of the plant, I'm just going to be playing around with some of the smaller branches that arise from those removing some shortening some with other shrubs, so you can cut them pretty much entirely to the ground in order to rejuvenate them. So this, this really include shrubs that have more of a suckering habit, if you will. So forsythia fits into this group. Certainly things like spy Ria, like ninebark, where you can go in and actually prune these plants right to the ground, and they're going to come right back. Or you can do more of a a staged approach, where you remove, let's say, a third of the oldest stems in the first year, half of the remaining old stems The next year, and then in the third year, you're going to remove the final batch of old stems, that's going to be a little bit less stressful for the plant than cutting it entirely to the ground. But those are kind of your two options for rejuvenating things. That's the approach I would take with lilacs for example, right be removing some of those oldest stems about a third that first year, half the next year, the remaining half the final final year. And I'm going to get a whole bunch of new shoots when I do that. And I'm just going to be thinning out the ones that are very small so the ones that are pencil are less than a pencil with in diameter are very, very close because a lot of times they do this you get a whole bunch of new shoots and then you do need to go in and send those out a bit. But it's a lot easier with with shrubs like that, that you can entirely cut back. But like I like I said with the needle evergreens, do a bit of research on exactly what type of shrub you have, and how it can be pruned so that you get the best possible response from that plant.
Nate Bernitz 54:59
So the Spring flowering trees and shrubs, those are kind of the exception. You're pruning pretty much all of these trees and shrubs and sort of late winter, early spring, except for plants that are actually blooming in the spring. Because if you're doing that you're just cutting off your flower buds. Right? Is that fair to say that they're the exception?
Emma E 55:22
That's exactly right. Yeah, especially for Spring Boot spring blooming shrubs, if you prune in the spring, before they start flowering, you're just removing those flower buds. So if you prune right after they've finished, then you're still gonna have a, you will have still gotten to enjoy that bloom. And you're gonna have a new crop of flower buds for next year.
Nate Bernitz 55:41
Emma, how do you help people from getting overwhelmed by pruning, there's so much information, I know that you could talk honestly for hours about the subject. Because there's so many details, so many considerations. But for anyone that is feeling overwhelmed, wondering, if I don't understand all this stuff, should I just not burn it all? Am I gonna make a mistake? How do you help people kind of ease into parenting, understanding that, yeah, you don't need to know every fact about parenting. To do it, they're just maybe a few basic things to know to at least get started.
Emma E 56:17
Yeah, pruning can be incredibly intimidating. And I have to say, when I first started, I was really, really nervous that if I cut the wrong thing, I was going to ruin a plant forever, I was going to totally destroy the way it looked maybe damage its health. But really, when it comes down to it, plants are incredibly resilient, if they're healthy, and as long as you aren't removing more than a third of the growth of that plant, or really of its of its total total mass, that it's gonna be okay. And there are few pruning cuts, if you've at least made a cut with with good technique, rarely is a plant beyond salvage. So, you know, there There are, of course, you know, really great pruning cuts, and there are some that that aren't so great. But rarely is there, you know, a total disaster situation. So even if you maybe didn't prune a shrub quite the way you should have or even if you're you're dealing with a young tree that you're trying to prune for the first time, that plant is going to produce new growth, and you are often going to get a second chance to prune it, you know, maybe in a more effective manner or a more attractive manner. That's better for the plant's health. So don't freak out, I guess, if you're really nervous, I'd say start with just removing branches that you're confident about. So go through and remove everything, that's, as I said, dead diseased or damaged. And then you can start looking for branches that are crossing or rubbing against one another. And once you've done all that, it's possible, you will have done everything that you needed to do. And you might just want to walk away at that point. Or if you're feeling a little bit more confident, then you can start to look at the actual branch structure within a plant and start to play around a bit with with making those cuts.
Nate Bernitz 58:23
And for you, you have this background of working at public gardens, Botanic Gardens. And you've just spent so much time around plants that look exactly how they're supposed to look, which gives you, I think, a really big leg up. Because when you look at these plants, you can see what it looks like. But you also know what it can look like. And so that gives you a leg up and manipulating its structure. Is it fair to say that, that's kind of a big part of burning is just knowing what plants can look like what they do look like when they're healthy and well maintained. And maybe the way to do that is to spend time at really well taken care of gardens.
Emma E 59:08
I think that that's true. Knowing what a plant looks like, at maturity, when it's been really well cared for and well pruned is is really helpful to know, it's not absolutely essential, but it is helpful. So if you can visit a botanical garden or you know another, you know, public garden space where plants have been really well cared for. It's not only going to give you ideas on what to plant, but also give you a sense of how that plant grows naturally. And, you know, you might might want to take a few pictures, jot some notes. And of course, you know, never hesitate to reach out to people that have more pruning expertise. Like me. Happy to answer your questions.
Nate Bernitz 59:56
Yeah, that's a good point. We're from UNH extension and anyone in New Hampshire, please don't hesitate to reach out to us you can actually email us pictures of the trees and shrubs that you're looking at ask for advice. We can maybe even annotate and point out some recommended places where we would cut or at least kind of give you the basics and weigh in on your situation. And whatever state you're from actually use your Cooperative Extension Service they, they're here to help and the Master Gardeners in your state are here to help as well.
Emma E 1:00:30
This episode's featured plant is witch hazel specifically Vernal witch, Hamamelis vernalis. Vernal witchhazel is a deciduous shrub that grows six to 10 feet tall and about eight to 15 feet wide. It's native to southern and central portions of the United States and hardy to zone four. Unlike common witch hazel, Hamamelis virginiana, which grows in the wild in New Hampshire and blooms in the fall. Vernal witchhazel blooms in late winter from late February to April depending on location, and it's potentially one of the earliest blooms in the landscape. Often alongside snowdrops. The blooms on Vernal witchhazel are spider like with four strap like pedals that range from pale yellow to reddish purple depending on the plant. The leaves are also really attractive with golden yellow fall color. If you have a good quality garden soil in your landscape that is well drained, organically rich and consistently moist. Vernal witchhazel could be the plant for you. As long as it's grown in full sun, you will definitely be enjoying winter blooms. fertile witch hazel would be one of my picks for a shrub border, woodland garden screen, rain garden or specimen plant. Check out your local nursery this spring for Vernal witchhazel. As always, I'd like to share a closing tip, this time on staking trees. New trees sometimes need stakes to hold them firmly in the soil until their roots become established. container or bare root trees may shift in the wind and could benefit from some temporary support. Note I said temporary. Large bald or burlap trees often don't need stakes because their root balls are heavy enough to prevent movement during moderately windy weather. However, smaller containerized trees might need a little bit of support to keep them from shifting until their roots are established. So if you think you need steaks for your new tree planting, you have a couple of options. The first is to drive three short steaks into the undisturbed soil around the tree and attach them to the trunk with a stretchable material. There are ties made just for this purpose that you should look at purchasing and using. Don't use garden hose and wire. These can actually girdle trees. If you use this standard system, make sure to remove the stakes a year from planting to avoid girdling the trunk and to promote structural strength of the trunk which comes from the tree being able to move just a little bit in the wind. Another option is to drive two or three wooden stakes into the soil against the side of the root ball. driving those stakes deep enough to be more or less level with the soil. This system does not require ties and the stakes do not need to be removed and will rot in place. This might actually be my preference. So staking trees can be a good thing in some cases. Just make sure if you're using Ties and More of a traditional system that you only keep those stakes in place for about a year.
Nate Bernitz 1:04:14
I really appreciate this time, Emma, this this has. This has been great. It's not a full class or anything on parenting. I mean, really, you need the visuals you need the hands on experience. But hopefully this is a good foundation for folks. We have some useful links in the show notes that I recommend checking out. Hopefully we'll get back soon to being able to do in person demonstrations of burning as well and as a fantastic teacher and once this pandemic is over with and we can get together safely. You'll definitely want to check out one of Emma's pruning demonstrations that she does in various parts of the state in the spring but this year has been an episode of Granite State gardening on ornamental pruning. We'll be back with future episodes on pruning, fruiting trees and shrubs. As we're getting into the spring here, we're going to do a lot more topics around, getting ready for a successful year and the garden, the orchard the landscape. That's what we're doing here. We're trying to set you up for success in your home garden and landscape. We welcome your feedback, your comments, your suggestions, you can email me and I at GSG dot firstname.lastname@example.org. We'd also appreciate your reviews. If you're listening on Apple podcasts, you can give us a five star review. We'd really appreciate it and anyone who's listening you can definitely share Granite State gardening with other gardeners and friends in your life that you think would benefit from listening to the podcast. Thanks for tuning in to Granite State gardening. Until next time, keep on growing and printing Granite State gardeners we'll see you next time. Granite State gardening is a production of University of New Hampshire Cooperative Extension and equal opportunity educator and employer views expressed on this podcast are not necessarily those of the universities, its trustees or its volunteers. inclusion or exclusion of commercial products on this podcast does not imply endorsement. The University of New Hampshire US Department of Agriculture and New Hampshire counties cooperate to provide extension programming in the Granite State learn email@example.com
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