From away to garden.com and Robinhood Radio.com, this is Away to Garden with Margaret Roach. You're a weekly invitation to dig in and grow. The earliest references to humans cultivating trees, stay back to maybe 6,000 BC and there are records of tree care tactics in the Bible too and from ancient Egypt. These person-to-tree interventions were the start of the science and art of arboriculture and are best practices of pruning and other how-to have evolved in each successive era to the methods that we know today. We're going to take a look backward in history and also explore some current recommendations with today's guest, Melissa Finley, the curator of Woody plants at New York Botanical Garden, so more in a moment but first these messages. Underwriting support for a way to garden provided by Colorblends wholesale flower bulbs, a third-generation bulb company offering top-sized flower bulbs directly to landscape professionals and ambitious residential gardeners on the web, Colorblends.com. And by High Moeng Seeds, Wolcott Vermont, Professional Quality Vegetable, Flower, and Urbal Seeds that are 100% organic and non-GMO project verified on the web, HighMoengSeeds.com. And by Whiteflower Farm, offering a wide range of carefully selected and expertly grown garden plants. On the web, whiteflower farm.com. Melissa Finley is New York Botanical Gardens thane curator of Woody Plants and also curator of NYBG's Peggy Rockefeller Rose Garden. Woody plants are her passion. She's a certified arborist and was a forester with the New York City Department of Parks and Recreation before joining NYBG four years ago.

And I'm so glad to welcome her to the program today. How are you?

I'm good. Thank you so much for having me.

In this craziest of winter so far, huh?

Up and down.

So unpredictable. I can't believe how hard it was raining about 10 minutes ago.

Yeah.

55 degrees. Yeah. Madness, madness. So speaking of tree-to-cares, just a little background like roughly how many zillion trees and shrubs are there at that botanical garden that you have to look at. What a complex question. I think we have about 5,000 mapped trees and shrubs, but many more that are unmapped and kind of unverified hanging out in our woodlands and natural areas. So it's hard to guess. You better stay on your toes, you guys. That's right. I think of having a small number of trees and shrubs as a big responsibility, but that's epic. We stayed busy, definitely. Yeah. I thought we could start with just a few highlights of the history of sort of mankind's attempts to manage trees. I know we could do like ten-hole episodes of the show on different theories and styles that we've evolved through the ages. But I wanted to sort of hear something that really stand out to you because I mean, I think trees have been on the earth close to like 400 million years or something. We homo sapiens are more like I don't know what a few hundred thousand years or something so it's they've been around a lot longer than we have. But what we've been cultivating them for like 6,000 years or something so any highlights for you. Yeah, so I became interested in this kind of early history of our relationship to trees. When I read some articles just about kind of the history of American art barriculture and kind of how we came to do our contemporary practices of tree pruning. And found that, you know, the kind of the basic articles that were available really stopped short in the late 19th century. So I really wanted to do a deep dive on kind of how people thought about trees and approached their relationship to trees much further back. So as you mentioned, yeah, our earliest kind of cultivation practices that we have records of are about 6000 BC in Asia Minor. But those records really do extend, you know, this is early olive tree cultivation and moving from Asia Minor into Italy by the sixth century BC, which is just remarkable infathomable really a amount of time.

And the other things I was looking for were just early mentions of intentional pruning.

There are several references to pruning of fig trees in the Bible.

They called dressing of sycamores, which refers to ficus

sycamores, which is the sycamore fig tree. And then the other very early mentions that we find in historical records, which I think were just fabulous, were actually from ancient Egypt. We have these wonderful paintings and records of actually the transplanting of large trees by the ancient Egyptians. There's records from the 15th century, which was during the reign of Hatshepsut, who was a very famous female Pharaoh, and she had sent people on an expedition to what we think is probably modern-day Somalia to bring back frankincense and murder trees for use in rituals. They extract those resins for mummy and balming and there's all these records of them very successfully transplanting these trees which to us seems so modern. Yes, oh. Wow. So, I didn't even know there was a female Pharaoh that she was into transplanting, having said she's transplanted. Yes, she's very interesting. Oh, fascinating. So, a long history, and it's gone through a lot of, you know, it's evolved. The practice has evolved I'd imagine the tools have evolved obviously there were no chainsaws and all kinds of things we have today bucket right buckets that went up into the tree tops and so forth but so you gave me when we first spoke about this you know just on, a couple of weeks back or whatever, you gave me some really interesting research papers to read. And it seemed like one of the subjects that had the most kind of differences was the pruning of mature trees, as opposed to the training of young trees when their first getting started. It seemed like with the older trees there was a lot more

not as well disparity, almost even differences of tactical approaches. Is that the case? Yes, definitely. I think as we've been able to codify our scientific approaches to pruning, that the way that we treat mature trees has a lot more

trying to think of the best way to put it, a lot more kind of disagreement, I'll say, in the field. Yes. How to approach these things. I mean, trees, you know, are very hard to study, and particularly. It's hard to do a PhD on the way that pruning affects a mature tree when you really do want to come back not one year later or two years later but 20 years later. How do we kind of do that sort of scientific study in that long of term is very difficult. So a lot of it is short term observation and kind of applying that as best we can to long-term understanding, which makes it all very difficult, yes. And I mean, I know a lot of Arborists just from the work I've done over the years and then also Arborists that were I live who have used, you know, used employed to help me with things they're too big for me to do with trees, with older trees. And there's a lot of difference of opinion, you know, as a consumer, as a garden owner, you know, who needs help. And so, and there's words that get thrown out, phrases that get thrown out, that like what's structural pruning, and then I've recently recently have heard about retrenchment pruning, and lots of seems disagreement about that. And you know, it's hard for the consumer to know what's the right way, yeah? It is. And unfortunately, it's difficult for the expert to know the right way as well. No. No. No. Um, what I'll say is, luckily for the home pruner, you know, trees that you can reach tend to be younger, trees. And those recommendations have not changed very much in the last few years. That's what we would call structural or formative perning. Is when we're approaching a juvenile tree, we're trying to establish a structure that will be long lasting that will allow for proper spacing between branches and reduce the instances of formation of bark inclusions and other things that might become what we would consider hazardous, you know, in the future. So that's kind of what we mean when we're talking about structural pername. So like in the old days we used to talk say the 3D's dead damaged in disease or some people had other ones but or things like crossed branches facing branches, or as you say, things that were a potential danger. Those are all structural things. Yes, absolutely. Yeah. So a lot of that comes out of the research from Ed Gilman, who's a fantastic researcher down at the University of Florida. And he did a lot of research on young tree structural pruning and that's where a lot of those phrases come from.

I think he might have even coined the three D's.

Okay.

And that's all kind of bog standard since I don't know how long ago, but his research

has really proved that it's, it seems to be good practice.

So yeah, you want to start with your three D's, eliminate crossers and then take take a big step back, put your saw down, and look at what you have left after you've eliminated those, and really just thinking about spacing and the overall shape of the canopy. So all of that is pretty much still recommended. But when we get into the mature trees, that's when it gets really much more complex. Yes. And so I've followed the work of some practitioner practitioners who really honor the tree through its whole life cycle, including through its decline into its death and its role in the ecosystem as you know, this biomass that was birthed there and will will lived there and will die there and you know wanting unless there's grave danger to people or structures to let it do its thing so to speak and then I've also again met people who do want to do adjustments to the canopy even of older trees or yeah so and I never know what's the right idea.

Yeah I mean so what I'll say is I think the more recent research we have more and more

is pointing to this incredible resilience that we have in trees throughout their whole lives.

So in the uh I'm trying to remember when this research was, there was some research done about tree life stages, where they were describing each phase of a tree's life, as you say, as they go from young to mature, to over mature in ancient and start to crumble, that describe these as inherent developmental stages. What the newer research is showing is that it's really best to think about several of those phases as response phases and not so much always going to happen at such and such age, at such and such period of a tree's life. So as it's starting to decline or change its canopy shape, these are signs that the tree is responding to the world around it, to the conditions it's experiencing, and it's actually actively reiterating its canopy in new ways in response to that environment. So the trees are really, really resilient. They're very perceptive of the world around them, and they're growing new wood, new structures in response to changing weather, and to changing branch shapes and all kinds of things. And the field is trying to really understand how trees are shaping themselves. And so over pruning is I think I kind of, I get it, you know, I feel that need to kind of prune these large trees in order to feel safer. But I think I'm kind of 10 towards the side of trusting them to to really to reiterate themselves and adapt to their environment over time as best we can. And then down to the level of like the individual cuts over the years I've heard you know different I've seen you know obviously there's very famous diagrams. I think some of them come from Alex Shigo or someone along the way that taught a lot of this. You know, and we hear about things like the, I was taught it was called the Branch Bark collar, but maybe it's just the bark collar and flesh cuts and how those cause greater wounds and what about when we get to that sort of, okay, I am going to make a cut for a particular reason. And there are some tree species that have very distinctive difference in the look of their tissue where the branch meets the trunk and some that don't. It's a lot. Right, yeah, absolutely. So yeah, it was very common practice to recommend flesh cutting. For a very long time, the oldest mention of it that I could find was from a book published in 1861 by a man called Dick Horvall. I'm not going to try to pronounce the French. It's totally butchered. I'm terrible at French so forget it, I don't mind. But the English translation, which was later published in 1864, was titled a treatise on perning forest and ornamental trees. And he was advocating for flesh cutting, which you know is cutting beyond that branch bark ridge directly kind of into the trunk tissue so that you get as flat a cut as possible. And his argument is that cutting that flost and even with the trunk will allow for more sap access to that wound since the sap is flowing upward in the xylem of the tree, the vascular tissues of the tree, that having it cut flesh against that trunk will expose all of the wound edges to actively flowing sap and would therefore close faster, which makes sense. And they have actually done studies that flesh cuts do those wound edges. Do start to seal over faster? But because they are a larger wound surface, over the course of about 10 years, they've done these AB testing and shown that eventually the branch bark ridge intact cuts do seal completely over much faster. But I was very interested in finding out why they were recommending that. And it really does make sense. It's accessing that sap that active wood might cause a faster regrowth. But now, do we, do my serverists go toward the outside, the collar, outside the ridge? Correct. Yes. So that all comes from Alex Shagos research, which was just fundamental in restructuring our understanding of trees. You know, he we kind of had to wait until we could look at trees with a little finer microscope and it kind of had to wait until we could look at trees with a little finer microscope. And it kind of had to wait until we had chainsaws, basically. It allowed him to really finely cut trees and look at different cross sections with a lot finer view, much more refinement to those cuts with the chain saw. It's an unbelievable scientific tool if you can believe it. So he started advocating in his 1977 report, part mentalization of decay and trees. This practice called natural target pruning. So it's replacing this flesh cut right against that stem of the tree with instead cutting just outside what you refer to as the branch bark rich. So it leaves just a little bit of a nub on the outside there. And the argument is that it both reduces the size of the cut, that cross section of wounded wood. And it retains this very specialized wood, which research has shown has this ability, the specialized ability to help seal over to occlude that wound much better than the stem tissue does. So that's compartmentalization is that place, is it a special place in it? Yeah. Yeah, so that tissue is much better at directing the chemistry of the tree to deposit micro-fighting chemicals and to physically seal off parts of the wood by depositing guns and just physically shutting off that area from from air. All of these invading fungus especially really needs needs air to live. So if you seal off with gums and all sorts of cool waxes, it's able to really functionally make a new wall. And that particular area of wood is much more physically and chemically able to do those functions. So speaking of like sort of 20th century developments, did we do things like cabling and so forth before then, or is that a modern day thing? Or I mean because there are now sort of support methods too that I see more commonly applied. Right, right. Well, so the steel Cling, which is a very common practice, that was invented by John Davy, who was an English arborist who moved to the US in the 1870s. And he wrote a book called The Tree Doctor in 1901, which introduced some of these steel cabling and steel brace rod techniques, but it's actually a much older approach. We have some evidence of the Greeks and Romans doing techniques like grafting and cabling and it's kind of tying together orchard and olive and vineyard plants and monks also mentioning it throughout the medieval period. But it was much more standardized in the early 20th century by people like John Davey and Francis Bartlett, probably the two most famous arborists from America. Whose names then became the names synonymous with large tree companies, and David Tree and Bartlett, yeah. That's right. Ha. Oh, I didn't know that it had an old history before that, that's interesting. So, you know, we have maybe like four, four, five minutes, and I wanted to ask you back at the Botanical garden. Are there tree species that sort of take the most resources in terms of your team, your arborist team, your tree care team there? Are there certain, like, high-need type, general of trees versus low-need? Do you know what I mean? Sure, sure. Yeah. It's an interesting question. Yeah, I mean, I think just looking at the trees themselves, I would say the number one thing that we are always responding to is white pines dropping their branches. And it's a wonderful adaptation, you know, they are adapted to kind of alpine conditions, frequent snow and ice loading and high winds, and rather than sustaining much greater damage, they just are adapted to kind of allow their branches to break off kind of brittle and very easily, to protect themselves. But yeah, they do make a big mess around here quite frequently. But then the broader question really is more about placement. So I've manufactured a rather complex system of inspections for safety for our trees, and that's primarily informed by the location of the tree and how many people are often around it rather than the tree itself. So, you know, if it's over a bench or a outdoor amphitheater or something like that, those are trees that I'm looking at much more priority. Yeah. And creating much more conservatively. Because for me, I would have guessed, you know, and again, I'm a gardener. It's not as extensive a collection by any means. But certain types of trees, like I have some very, very old apple trees and I have a number of old magnolias seem to get where they have had wounds, so to speak, on their branches. They tend to get a lot of like water sprouting kind of bad hair day looking. Yes, say do. Growth, and that to me is a lot of work,

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