Talking Trees

David Lonsdale

• Arboricultural Academy • Season 2025 • Episode 125

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In this episode, listeners meet renowned arboricultural expert David Lonsdale. David shares his inspiring journey and extensive experience, discussing his insights on tree pathology, tree risk assessment, and management strategies that promote healthy urban forests. He provides practical knowledge blended with anecdotes from his long career, highlighting the importance of continuous learning and adaptation in the evolving field of arboriculture.

Background information:

  • David Lonsdale :: British Mycological Society
  • Home All Journals Arboricultural Journal List of Issues Volume 46, Issue 4 A short tribute to the late Dr David Lon
  • Webinar: Tree Decay a few questions still worth asking with Dr David Lonsdale


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Roger:

Talking Trees with Lillian Jadd. Welcome to Talking Trees. Today we pay tribute to Dr David Lonsdale, a distinguished figure in arboriculture and entomology. Drawing from resources by the Arboricultural Association and the British Mycological Society, we'll review his significant contributions to mycology, nature conservation and tree health. We'll also reflect on his legacy as detailed in the Arbora Cultural Journal and revisit insights from his webinar on wood decay and tree defense. Let's begin.

Jad:

Welcome in everyone ready to dive into another fascinating figure in arboriculture.

Lilly:

Absolutely Always excited to learn more.

Jad:

Today we're going to explore the life and career of Dr David Lonsdale.

Lilly:

Ah, a true legend in tree care and assessment. His work still resonates so strongly today.

Jad:

It really does, and you know it's interesting, we have a pretty diverse set of sources for this one, which I think will give us a really well-rounded picture of his contributions.

Lilly:

Oh, that's great. What have you gathered?

Jad:

Well, we've got some excerpts from the Arbor Cultural Association website, including a piece specifically about Lonsdale titled Remembering David Lonsdale.

Lilly:

Sounds like a good place to start. Get some personal reflections on his character and impact.

Jad:

Exactly, and to complement that, we also have some insights from the British Mycological Society's website, which I thought was fascinating.

Lilly:

His work spans so many disciplines, it's no surprise to see that connection.

Jad:

Right, and of course, we've got the more academic side covered, with a tribute from the Arboricultural Journal and, to top it off, a YouTube video of a webinar Lonsdale hosted for the Arboricultural Association.

Lilly:

Fantastic A webinar. You say what was the topic.

Jad:

Tree decay Always relevant right.

Lilly:

Absolutely Never a dull moment with tree decay.

Jad:

So let's start with the man himself. The articles paint such a warm picture of his personality Kind, approachable, humble. Apparently he was a great listener with a fantastic sense of humor.

Lilly:

And, of course, a meticulous scientist. That goes without saying.

Jad:

Absolutely. He was often described as a true gentleman.

Lilly:

It really does shine through in everything we've read about him.

Jad:

There's this one anecdote about attendees at his funeral that I found really striking.

Lilly:

Oh, tell me more.

Jad:

While some people there only knew him as an entomologist.

Lilly:

Right right.

Jad:

While others only knew him as an entomologist, right right. While others only knew him as an arborist, it seems like no one fully grasped the breadth of his expertise.

Lilly:

Wow. It really highlights just how deeply immersed he was in both of these you know seemingly separate fields, and how he managed to bridge the gap between them. It speaks volumes about his intellectual curiosity, his ability to see these connections where others might not.

Jad:

He sounds like he had a bit of a playful, quirky side too. One article mentions him cycling around on a tricycle.

Lilly:

A tricycle. That's adorable.

Jad:

And there's that story about him walking backward downstairs after an injury.

Lilly:

That's fantastic. It really makes him feel so much more I don't know human and relatable.

Jad:

It does. So how did this multi-talented individual find his way into the world of arboriculture?

Lilly:

His journey began in 1975 at the Forestry Commission's research division.

Jad:

Which later became Forest Research.

Lilly:

Exactly and that's where he really dove into tree disease, decay and safety research, particularly pruning wounds and the whole process of decay that follows.

Jad:

I find it fascinating that his research was happening at the same time as Alex Shigo's work. You know, a true icon in arboriculture.

Lilly:

I can only imagine what it must have been like working, as one article puts it, in Shigo's shadow.

Jad:

It speaks to his dedication for sure.

Lilly:

Absolutely. While Shiba might have been in the spotlight, Lonsdale's research was providing that crucial scientific evidence to support many of Shigo's observations and theories.

Jad:

Laying the groundwork, really solidifying those foundations for so many practices we use today.

Lilly:

Without a doubt, and on top of his research, he also made time to mentor the next generation of arborists. He was an examiner for the Royal Forestry Society's professional diploma in arboriculture.

Jad:

Wow, talk about a commitment to sharing knowledge.

Lilly:

And shaping the future of the field.

Jad:

Then, in 1999, came the publication that so many consider his masterpiece the Principles of Tree Hazard Assessment and Management, the Bible of Tree Inspection, as it's often called.

Lilly:

Oh, absolutely. It wasn't just a collection of research findings. He had this incredible talent for taking complex scientific information and presenting it in a way that was accessible to practitioners.

Jad:

He wasn't just speaking to scientists. He was talking directly to the people out there caring for trees every day.

Lilly:

Precisely, he knew how important it was to bridge that gap between research and application, ensuring that the latest scientific knowledge could be translated into real-world strategies.

Jad:

And speaking of practical application, his involvement with the Ancient Tree Forum really highlights his dedication to conservation.

Lilly:

Oh, absolutely. A passionate advocate for ancient trees, recognizing their immense value both ecologically and culturally, and that's where we see some of his most insightful observations come to light. Immense value both ecologically and culturally, and that's where we see some of his most insightful observations come to light.

Jad:

This is where things get really interesting. I came across a story about Ted Green, another big name in ancient tree conservation. Apparently, Lonsdale challenged a widely held belief that fungal brackets were the main cause of decay.

Lilly:

Interesting. I can see how that encounter would be pivotal for Green, pushing him to explore the complexities of tree decay in more depth.

Jad:

It says so much about Lonsdale's ability to not just teach but to inspire, to make people think critically about what's going on inside a tree.

Lilly:

It wasn't about just accepting what was commonly believed.

Jad:

It was about questioning, looking for evidence, always seeking a deeper understanding, looking for evidence, always seeking a deeper understanding, and his insights went beyond challenging existing assumptions. He made some groundbreaking observations of his own, like how old trees essentially divide themselves into these individual functional units. They're often called Lonsdale units now.

Lilly:

Ah yes, imagine a mature tree, one that's experienced decay or damage over time. You might think it's on the decline, but Lonsdale observed that these trees often compartmentalize. They form these semi-autonomous sections.

Jad:

So it's like the tree has its own internal backup system.

Lilly:

Exactly. Each Lonsdale unit operates almost independently, with its own set of branches connecting wood and roots, all working together to support that section.

Jad:

Amazing that's incredible Trees are so much more resilient than we give them credit for.

Lilly:

It really highlights the remarkable adaptability, especially for veteran and ancient trees, and this concept has profoundly changed how we assess and manage these trees.

Jad:

Makes you look at an old tree, maybe one that looks a bit worse for wear, with a newfound respect, doesn't it?

Lilly:

It does. There's a whole network of life still thriving within it.

Jad:

It reminds us that we need to see beyond the apparent damage and recognize these incredible survival strategies that these trees have developed over time. Which leads us to another fascinating area of Lonsdale's research his work on tree decay and how it relates to the health and safety of trees.

Lilly:

He was meticulous in his research, studying various tree species and how decay develops and ultimately impacts a tree's structure.

Jad:

And he didn't shy away from tackling controversial topics either, like the role of wound paints in tree care.

Lilly:

Ah yes, His research on wound paints was revolutionary. It really changed our understanding of how trees respond to injury.

Jad:

You know it used to be standard practice to just slap some wound paint on any cut or damage.

Lilly:

Right, the go-to solution.

Jad:

But his findings challenged the effectiveness and even the safety of this approach.

Lilly:

What was particularly intriguing was his discovery of latent fungi in sapwood.

Jad:

Latent fungi. What are those?

Lilly:

These are fungi that naturally exist within the wood but remain dormant until the conditions are right for them to grow. Often that's triggered by injury or stress.

Jad:

So even if you put wound paint on, the fungi might already be inside the tree.

Lilly:

Exactly. It really shifted our thinking about wound care, highlighting the limitations of wound paints and promoting practices that support the tree's own defenses.

Jad:

So instead of trying to create an artificial barrier, we should focus on helping the tree heal itself naturally.

Lilly:

That's the idea, it seems. Lonsdale was always pushing boundaries, questioning conventional wisdom and seeking new and innovative approaches to tree care.

Jad:

And that drive led him to a topic that was quite novel at the time biocontrol agents.

Lilly:

Ah yes, Using natural organisms to manage tree diseases.

Jad:

It sounds almost like something out of science fiction.

Lilly:

It was certainly a bold concept. He did groundbreaking research on a particular strain of naturally occurring fungus that showed real promise in controlling decay in pruning wounds.

Jad:

So instead of chemical treatments, we could potentially harness the power of nature itself to protect trees. That's incredible. What happened with that research?

Lilly:

Well, unfortunately, it ran into a roadblock. New pesticide regulations came into effect, making it incredibly expensive to register this biocontrol agent. The research was essentially abandoned.

Jad:

That's such a shame, especially with the growing concerns about the environmental impact of pesticides.

Lilly:

It's a reminder that scientific progress isn't always straightforward. Sometimes, valuable research gets sidelined for reasons outside the control of the scientists.

Jad:

It highlights the importance of continued investment in research, particularly in areas like this that offer such promising and sustainable solutions to the challenges we face.

Lilly:

Absolutely. And while Lonsdale's work on biocontrol might have been cut short, his pioneering spirit paved the way for future research in this vital area.

Jad:

It's a testament to his vision, his willingness to explore all avenues for improving tree care, and really it's just the beginning of understanding the breadth and depth of Lonsdale's contributions to the world of arboriculture.

Lilly:

I'm eager to dig deeper into his work and see what other gems we can uncover. It really is, and it wasn't just about finding those practical solutions. Lonsdale also delved into these deeper philosophical questions about our relationship with trees and, well, nature in general.

Jad:

Oh, interesting Like what.

Lilly:

In his webinar he talks about how we tend to view decay in a negative light.

Jad:

Yeah, I could see that.

Lilly:

We're so focused on trees as a commodity, as a source of timber or other products. But from the tree's perspective, decay is just a natural process, part of its life cycle.

Jad:

That's a powerful shift in perspective.

Lilly:

He encourages us to see decay not as a weakness, not as a disease, but as this integral part of the natural world.

Jad:

Right Providing habitat for other organisms contributing to nutrient recycling. Natural world Right Providing habitat for other organisms contributing to nutrient recycling Exactly.

Lilly:

He even points out that we, as humans have benefited from decay processes throughout history finding shelter in the hollows created by decay.

Jad:

It's true, it really challenges us to reconsider that very human-centered view we often have of nature To recognize the value of all living things, even in their decay. It's a humbling thought. Even in death, trees continue to give back to the ecosystem.

Lilly:

Supporting a whole web of life that goes far beyond our own needs.

Jad:

We're just a small part of something so much bigger.

Lilly:

Exactly. The health of the planet depends on the well-being of all its inhabitants, from the tiniest fungi to those grand old trees.

Jad:

Lonsdale also tackled this question about whether decay fungi are really parasites or pathogenic.

Lilly:

Right, challenging how we traditionally think about fungi in the forest.

Jad:

So he's questioning those labels.

Lilly:

He argues that terms like parasite and pathogen are often well human constructs based on our perception of fungi as harmful.

Jad:

Right, we see a fungus on a tree and automatically assume it's bad news.

Lilly:

He uses this example of a fungus fruiting on a living tree. We see that fruiting body and assume it's causing harm.

Jad:

But it might just be living on the dead tissues.

Lilly:

Exactly Not actually harming the living parts of the tree. He acknowledges that some fungi can of course attack and kill living tissues, but suggests that in many cases the relationship between fungi and trees is much more complex.

Jad:

More of a balancing act.

Lilly:

Right, it's this delicate balance between the tree's defenses and the fungus's ability to overcome those defenses.

Jad:

He calls it co-evolution right.

Lilly:

Yes, trees and fungi have evolved together, developing intricate strategies for both defense and attack.

Jad:

Kind of like an ongoing arms race.

Lilly:

Precisely, and sometimes this co-evolution leads to a kind of harmonious coexistence where both the tree and the fungus actually benefit.

Jad:

Interesting, like a symbiotic relationship.

Lilly:

Think of fungi that colonize the heartwood of certain species like oak or yew. They break down the heartwood, creating cavities that can provide valuable habitat, but they don't typically invade the living sapwood, so the tree can keep thriving. But I imagine there are also cases where that balance tips and the fungus becomes more aggressive Of course, honey fungus is a prime example, a notorious root pathogen that can be devastating, and there are also fungi that produce toxins that can weaken the tree's defenses, allowing the fungus to spread.

Jad:

So it's not a simple black and white situation, it's a spectrum.

Lilly:

A spectrum of relationships, from benign coexistence to outright attack, and the context matters too.

Jad:

Right. A fungus that might be relatively harmless in a natural forest could become a serious threat in a stressed urban environment. Exactly.

Lilly:

Pollution, compaction all those urban stressors make trees more vulnerable.

Jad:

So we need to consider the specific tree, the environment and the potential risks when assessing the impact of a particular fungus.

Lilly:

Absolutely, and Lonsdale pointed out that our understanding of these relationships is constantly evolving.

Jad:

What we might consider a pathogen today could be seen differently in the future.

Lilly:

As our knowledge grows, our perspective shifts.

Jad:

It's a reminder to be open to new research and be ready to adapt our practices.

Lilly:

To approach tree care with a healthy dose of humility, recognizing there's still so much we don't know.

Jad:

Which brings us back to those wound paints. For so long they were considered a must-have in tree care, but Lonsdale's research really challenged that.

Lilly:

He found that a lot of the claims about wound paints, especially their ability to prevent decay, weren't actually backed up by evidence.

Jad:

So they weren't as effective as people thought.

Lilly:

He talks about how wound paints often failed to adhere properly, creating these pockets where moisture could get trapped, actually making it a better environment for fungi to grow.

Jad:

Oh wow, so it could backfire.

Lilly:

And, as we talked about earlier, the discovery of those latent fungi in the sapwood meant that wound paints weren't necessarily keeping fungi out.

Jad:

Because they were already there.

Lilly:

Exactly. He even found that some wound paints contained chemicals that could harm the tree's tissues, slowing down the healing process.

Jad:

So instead of promoting healing, they might actually hinder it.

Lilly:

His research really shifted the focus away from trying to create this artificial barrier and towards supporting the tree's natural defenses.

Jad:

So proper pruning techniques become even more crucial.

Lilly:

Minimizing wound size, helping the tree to compartmentalize effectively. He didn't completely dismiss wound paints, though he suggested that in some cases a very durable wound paint could potentially be helpful in restricting decay, especially if it prevents the wood from drying out too much, which can make it more susceptible to fungi.

Jad:

So there might be a place for it, but it's not a one-size-fits-all solution.

Lilly:

Exactly, and the main focus should always be on those natural defenses. Wound paints should be used carefully, if at all.

Jad:

It all comes back to critical thinking, evaluating the evidence, weighing the pros and cons, not just blindly following what's always been done.

Lilly:

That's the essence of good arboriculture.

Jad:

And Lonsdale's research has had such a huge impact on how we approach tree care today.

Lilly:

Speaking of impact, his work on biocontrol agents was truly pioneering.

Jad:

Right, using those natural organisms to fight tree diseases. Such a fascinating concept. He got some promising results, but those regulatory hurdles got in the way.

Lilly:

Unfortunately, yeah, new regulations made it too expensive to register the biocontrol agents, so the research was pretty much stopped.

Jad:

What a shame, especially with the growing concerns about the environmental impact of conventional pesticides.

Lilly:

It was a setback, but his work in that area really laid the foundation for future research. There's a renewed interest in biocontrol agents now as a more sustainable approach.

Jad:

Hopefully we can pick up where you left off.

Lilly:

I think we will, and it's a reminder that scientific progress isn't always a straight line. Sometimes valuable research gets put on hold, but Lonsdale's legacy goes beyond those individual research projects.

Jad:

It's about that critical thinking, questioning assumptions and really understanding the complex processes involved in tree care.

Lilly:

His work continues to inform our practices today. His questions are still sparking new research directions. His impact will be felt for a long time to come.

Jad:

In one of the articles there's a quote from Lonsdale that stuck with me. He said it is therefore with hope for the future care of this great heritage that I approach the end of my work on this book Really captures his dedication to trees and to passing on that knowledge.

Lilly:

Beautiful and it's a call to action for all of us in arboriculture to continue his legacy Research, education, advocacy all essential for a healthy urban forest.

Jad:

Well said, his work wasn't just about those practical fixes. It was about expanding our understanding of how nature works.

Lilly:

Giving us that deeper sense of purpose and responsibility in our work as arborists.

Jad:

He was a scientist, an educator and a true advocate for trees, and his influence is still felt today.

Lilly:

Absolutely. He reminds us that there's always more to learn, more to discover, more to appreciate about these incredible trees.

Jad:

So, thinking about your own work, what aspect of David Lonsdale's research has resonated most with you? How do you see yourself applying his insights?

Lilly:

That's a good question. Maybe it's that emphasis on observation, really taking the time to see the tree, its history, its strengths and weaknesses. Or perhaps it's that commitment to research, always questioning, seeking evidence, not just relying on assumptions.

Jad:

Or maybe it's that passion for ancient trees, recognizing their importance and working to protect them.

Lilly:

Right. Whichever part speaks to you, I encourage you to explore it further. Dive into his publications, the principles of tree hazard assessment and management, his work on those Lonsdale units.

Jad:

So much valuable knowledge to be gained from those resources.

Lilly:

They can really enhance your understanding of tree biology. And as you move forward in your career, remember Lonsdale's commitment to education share your knowledge, mentor others, help our profession to grow and evolve.

Jad:

Never stop questioning, never stop learning and never lose that passion for trees.

Lilly:

Well said.

Jad:

I'll leave you with a final thought. Do you think Lonsdale's passion for both entomology and arboriculture gave him that unique perspective on the interconnectedness of nature, and how might that perspective inform your own approach to tree care?

Lilly:

Something to think about as you continue your work in this important field.

Jad:

Until next time, keep exploring, keep learning and keep caring for our amazing urban forests.

Roger:

Thank you for joining us on this episode of Talking Trees. Today we reflected on the remarkable legacy of Dr David Lonsdale, drawing insights from the Arboricultural Association, the British Mycological Society, the Arboricultural Journal and his own webinar. We hope this discussion has provided a clear overview of his contributions to arboriculture entomology and mycology. We appreciate your attention and look forward to our next conversation.

People on this episode

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Jaroslav Kolařík

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Denisa Grábner

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Josef Grábner

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